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Structural characterization of electron‐beam crosslinked thermoplastic elastomeric films from blends of polyethylene and ethylene‐vinyl acetate copolymers
Journal of Applied Polymer Science
Abstract
Films were prepared from a blend of low-density polyethylene (LDPE) and ethylene-vinyl acetate (EVA) containing 45% VA and ditrimethylol propane tetraacrylate (DTMPTA). Electron-beam initiated crosslinking of these films was carried out over a range of radiation doses (20–500 kGy), concentrations of DTMPTA (1–5 parts by weight), and blend compositions. The IR studies revealed that oxidation and crosslinking dominated up to an irradiation dose of 100 kGy. At higher irradiation doses chain scission and disproportionation predominated among all the competitive processes for the 50:50 blend without DTMPTA. The gel fraction of the films increased with the increase in irradiation dose, DTMPTA level, and EVA content of the blends. X-ray diffraction and differential scanning calorimetry studies showed that the crystalline portion of the blends was only affected by radiation at higher irradiation doses (≥200 kGy). Scanning electron microscopy studies indicated that in the 50:50 blend the LDPE formed the continuous phase, which was further confirmed by atomic force microscopy and transmission electron microscopy studies. However, a co-continuous morphology was formed when the EVA content was increased. When DTMPTA was added to the blends (≥3 wt %), the 50:50 blend exhibited a co-continuous morphology. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1936–1950, 2001
... They also reported that at a constant irradiation dose, increment of EVA composition led to reduced heat shrinkage. Chattopadhyay et al. also investigated thermo-physical properties and structure of electron-beam crosslinked films of PE/ EVA blend (Chattopadhyay et al., 2001a(Chattopadhyay et al., , 2001b. It was shown that the modulus and tensile strength increased and the permanent set decreased with increase in the radiation dose (Chattopadhyay et al., 2001a). ...
... The dynamic mechanical thermal analysis data revealed two-phase structure of PE/EVA blends and that the glass transition temperatures (T g ) of the blends were increased by irradiation (Chattopadhyay et al., 2001a), as also reported by Sethi et al., 2000). It was also found that the crystalline portion of the PE/EVA blends was influenced only at radiation doses higher than 200 kGy (Chattopadhyay et al., 2001b). ...
... While the presence of a radiation sensitizer changed the morphology type, the microstructure of the blend was not affected by irradiation (Chattopadhyay et al., 2001b). Dalai and Wenexiu examined the factors affecting the irradiation crosslinking of LDPE/EVA blends (Dalai and Wenxiu, 2002). ...
Gel content, mechanical properties and morphology of immiscible PE/EVA blends irradiated by high energy electron beam were studied. The results of gel content measurements showed that the capability of cross-linking of the blend samples increased with an increase of the EVA composition. Also, the gel content for most compositions of the blends displayed a positive deviation from the additive rule. The results of mechanical properties showed that the tensile strength and elongation at break of the samples increased and decreased, respectively, with irradiation dose. On the other hand, the mechanical properties of the irradiated blends also depicted a positive deviation from additive rule contrary to the un-irradiated blends. A synergistic effect observed for the mechanical properties improvement of the irradiated blends and it was attributed to the probable formation of the PE-graft-EVA copolymers at the interface of the blends during the irradiation process. A theoretical analysis revealed that irradiation induced synergistic effect was more significant for EVA-rich blends with weaker interfacial interaction as compared to PE-rich blends. The morphological analysis indicated that the blend morphology was not affected obviously, whereas it was stabilized by irradiation.
... On the other hand, many efforts and energy are used to over- come the problems caused by plastic wastes, particularly those produced every year by the packaging industry. Increasing costs for the removal, incineration and landfill of municipal wastes urge the packaging industry to shift their productions to more sustainable packages ( Brogly et al., 1997). In this study, we also consider the applicability of biodegradable re- sins for multilayer packaging, and in particular for seal layer. ...
... It also decreases the enthalpy of melting and shifts the melting point to lower temperatures. By increasing the EVA content, another melting peak appears at lower temperatures due to EVA chains crystal formation, which contain sequences of ethylene groups capable of forming fine lamellas ( Brogly et al., 1997). ...
... It should be mentioned here that it was not possi- ble to add the PE-g-ma compatibilizer because of FDA restric- tions concerning contact with food. Finally, because of the large difference in viscosity of the re- sins, as illustrated in Fig. 6, the morphology developed in the film blowing die could not be of the droplet-matrix type but rather co-continuous structure as reported in literature (Chattopadhyay et al., 2001;Peón et al., 2003). The complex viscosity ( g *) of LDPE and EVA resins in Fig. 6s hows al arge differ- ence in their viscosities at shear rates in the range of the film blowing process. ...
Seal strength behavior of low density polyethylene and ethylene vinyl acetate copolymer (PE/EVA) blends as well as that of blends of a seal grade PLA with aliphatic polyester (PCL) was studied. Polyethylene is commonly used for seal application in packaging multilayer structures and amorphous PLA is considered to be its counterpart for compostable and/or biodegradables ones. Incorporation of EVA in polyethylene improves its sealability in terms of a decrease in seal initiation temperature and broadness of sealability plateau. This was interpreted as due to the formation of finer crystals, a decrease in the melting point and presence of vinyl acetate polar group. These were supported by results obtained from differential scanning calorimetry (DSC) and Scanning electron microscopy (SEM). For the PLA/PCL system, the dispersed phase was stretched into elongated ellipsoidal domains. This type of morphology affected the mechanical and seal properties of the blends. As a result of blending, both hot-tack initiation temperature and strength as well as seal initiation temperature were enhanced. The enhancement in these seal properties was significant when the concentration of the dispersed phase exceeded 20 wt% in the blend. Hot-tack strength of up to twice of pure PLA was achieved through blending. This was attributed to the lower glass transition temperature of PCL, resulting in enhanced mobility of PLA chains and also the high aspect ratio of the dispersed phase. The maximum obtained hot-tack strength (1 200 g/25 mm) at 40% dispersed content compared advantageously to commercially available polyolefin based sealant resins. The seal and hottack initiation temperatures were shifted to lower temperatures by as much as 30°C, which can allow faster and more energy efficient sealing process.
... Where A 1738 is the absorbance of the ketonic carbonyl stretching vibration 20 at 1738 cm À1 and A 2850 is the absorbance of the methylene C-H symmetric stretching vibration at 2850 cm À1 ; the latter absorption is an internal standard that compensates for differences in film thickness. 21 Results and discussion Crosslink evaluation and phase morphology of irradiated nanocomposites Generally, the yield of irradiation-induced crosslinking can be estimated from the gel fraction results. 22 The gel fraction yield increased with increment in irradiation dosage, as shown in Figure 1. ...
... These indicate that not all the cations on the surface of the silicate layers were substituted with octadecylamine Figure 8 shows the variation of area under absorbance at 1462 cm À1 as a result of C-H bending of >-CH 2 . 21 It is clear that the absorption increases at 100 kGy and then decrease at 200 kGy for the neat EVA/SMR L and its nanocomposites. Large amount of free radicals are formed at 100 kGy due to chain scission, 30 thus increase >-CH 2 , whereas at 200 kGy this radicals can recombine and form crosslinking. ...
... This peak corresponds to C-O stretching. 21 At 0 and 8 phr organoclay loading, the area increased up to 100 kGy and then decreased at 200 kGy. At 100 kGy irradiation dosage degradation due to oxidation is dominant. ...
The effects of organoclay loading and electron beam irradiation on the crosslinking and degradation of ethylene(vinyl acetate) copolymer (EVA)/natural rubber, grade Standard Malaysian Natural Rubber (SMR L) nanocomposites was studied. The nanocomposites were prepared through the melt blending technique with the ratio of EVA: SMR L fixed at 50:50 and organoclay loading varied from 0 to10 phr. The samples were irradiated using a 3.0 MeV EB machine with doses ranging from 50 to 200 kGy. At irradiation dose 50–150 kGy organoclay reduces the crosslinking yield significantly as evidenced from the gel fraction results and thus, storage modulus decreases and tan deltamax values increases for the nanocomposites compared to neat EVA/SMR L. However, at 200 kGy the crosslinking yield was not much affected by the organoclay and thus, the storage modulus increased and tan deltamax decreased. Scanning electron micrograph images show that different level of irradiation dose form different phase morphology on the nanocomposites. Analysis on Fourier transform infrared spectrums and carbonyl index values proved that the nanoscale dispersion and barrier effect of organoclay influence the crosslinking and degradation of the nanocomposites thus gives a significant effect on the dynamic mechanical properties.
... A band of several peaks resulted from oxidative degradation due to gamma irradiation appears in the range of 875-1370 cm −1 . This band may be attributed to CO stretching and OH bending [61,62]. Another additional peak showed upon irradiation around 1720 cm −1 . ...
... Another additional peak showed upon irradiation around 1720 cm −1 . This peak was reported by many researchers and it corresponds to CO bond stretching in carbonyl groups formed due to oxidation as well [27,29,40,62,63]. Finally, a new peak can be observed around 3680 cm −1 ; this peak may be attributed to the stretching of OH bond in alcohol groups as an oxidation product post-irradiation [64]. ...
Effect of gamma radiation on the mechanical and structural properties of polylactic acid (PLA) and high-density polyethylene (HDPE) is analyzed. Samples were irradiated in ambient conditions with doses in the range of (0–175 kGy) using 60Co gamma irradiation facility. Experimental results showed a clear effect of gamma radiation on polymer properties through the action of crosslinking, chain scission and oxidative degradation. Tensile testing results for both polymers showed a decrease in the tensile strength and ductility at high irradiation doses, suggesting that the effect of both chain scission and oxidative degradation is dominant over crosslinking for higher doses. Results from Fourier transform infrared (FTIR) spectroscopy show that signature peaks of both PLA and HDPE were present after irradiation indicating that exposure to gamma radiation does not lead to diminishing their corresponding structural modes. Nevertheless, new peaks were observed upon irradiation of HDPE samples. These new peaks are attributed to modes of different oxygen bonds in oxidation products such as carbonyl groups and alcohol groups. Finally, X-ray diffraction (XRD) results show that both polymers exhibit increased crystallinity with increased radiation exposure due to chain splitting that is stimulated by oxidative reactions.
... Irradiation doses were commonly used in the presence of cross-linking agent, such as trimethylol propane trimethylacrylate (TMPTMA) or ditrimethylol propane tetraacrylate (DTMPTA), in blends containing iPP/LDPE 53 or LDPE/EVA, 54,55 respectively. In such blends, irradiation in the presence of trimethylol propane acrylates was particularly efficient, regarding tensile strength, when the LDPE content was high. ...
... Irradiation of LDPE/EVA blends has been extensively studied because of their particular interest as heat-shrinkable materials for the wire and cable industry. [45][46][47][48][49]54,55,74,[97][98][99][100][101][102][103] Heat-shrinkable materials are kind of shape memory materials with heat as their stimulus. ...
... Such reduction in C-H stretching peak intensity may be ascribed to the hydrogen abstraction and resulting crosslink formation in the EVA phase upon irradiation. [27,33,34] ...
... The T g value of the blends further increases after EBR and it can be associated with the formation of three dimensional network in EVA phase that cause severe restriction in chain mobility. [27,33] The melting temperature corresponding to EVA does not show much change in the MDI-modified blends. However, after electron beam irradiation, there is a significant reduction in the melting temperature and the T m was found to decrease with increasing radiation dosage. ...
Ethylene vinyl acetate (EVA)/thermoplastic polyurethane (TPU) blend at various blend ratios has been modified via reactive processing with 4,4′-methylene diphenyl diisocyanate (MDI). Modification of the blends with even small amount of MDI shows significant improvement in physico-mechanical properties for EVA/TPU 50/50 and 30/70 blends, and it is also supported by the superior melt rheological behavior and dramatic improvement in oil resistance property. After the treatment of electron beam (dose range: 50–150 kGy), radiation crosslinked EVA/TPU (30:70) blend reveals further improvement in various properties. This particular material can find potential application as cable sheathing component.
... The X-ray diffraction (XRD) patterns of ZnO nano-particles prepared at various annealing temperatures were recorded by the D8 The area under the crystalline and amorphous portions was determined in arbitrary units and the degree of crystallinity (Dc) was calculated using the relation [9]. ...
... where Ia and Ic are the integrated intensity corresponding to amorphous and crystalline phases, respectively. Also, the grain size (t), interchain distance (r), interplanar distance (d) and distortion parameter (lattice strain) (g) were calculated as follows [9][10][11]: ...
ZnO nano-particles have been synthesized by simple chemical route using a starting solution consisting of zinc acetate and citric acid as a surfactant agent. The structural properties of the prepared ZnO nano-particles annealed at different temperatures have been characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. The XRD patterns show ZnO-wurtize phase in the nano-powders, and size of crystals increases by increasing the annealing temperatures. The TEM images show nano-particles as clusters with size in the range of 10-20 nm. Electron diffraction pattern of nano-powders annealed at 900°C temperature shows a well distribution of spherical particles due to the effect of citric acid as surfactant in chemical process. Thick films prepared by screen printing technique from zinc oxide nano-powders annealed at different temperatures (500–900 °C), characterized by SEM analysis and tested for various gases. The film prepared from ZnO powder annealed at 700°C shows the higher sensitivity to H 2 S gas for 10 ppm gas concentration.
... Irradiation doses were commonly used in the presence of cross-linking agent, such as trimethylol propane trimethylacrylate (TMPTMA) or ditrimethylol propane tetraacrylate (DTMPTA), in blends containing iPP/LDPE 53 or LDPE/EVA, 54,55 respectively. In such blends, irradiation in the presence of trimethylol propane acrylates was particularly efficient, regarding tensile strength, when the LDPE content was high. ...
... Irradiation of LDPE/EVA blends has been extensively studied because of their particular interest as heat-shrinkable materials for the wire and cable industry. [45][46][47][48][49]54,55,74,[97][98][99][100][101][102][103] Heat-shrinkable materials are kind of shape memory materials with heat as their stimulus. ...
... The peaks (*) marked are attributed to alumina. The area under the crystalline and amorphous portions was determined in arbitrary units and the degree of crystallinity (Dc) was calculated using the relation [22]. ...
... where Ia and Ic are the integrated intensity corresponding to amorphous and crystalline phases, respectively. Also, the grain size (t), interchain distance (r), interplanar distance (d) and distortion parameter (lattice strain) (g) were calculated as follows [22][23][24]: ...
The effect of variation of annealing temperature on the gas sensing characteristics of SnO2 thin films, which have been prepared by spray pyrolysis on alumina substrate at 350 oC, is investigated systematically for various gases at different operating temperature. The XRD, UV-visible spectroscopy and SEM techniques were employed to establish the structural, optical and morphological characteristics of the materials, resp. The X-ray diffraction results showed an increase in the crystallinity at higher annealing temperature. A high value of sensitivity is obtained for H2S gas at an optimum temperature of 100 oC is improved considerably. A SnO2 gas sensor annealed at 950 oC with sensitivity as high as 24 %, 4 times higher than that of sensor annealed at 550oC, are obtained for 80 ppm of H2S. The degree of crystallinity and grain size calculated from the XRD patterns has been found increasing with annealing temp
... The X-ray diffraction (XRD) patterns of ZnO nano-particles prepared at various annealing temperatures were recorded by the D8 The area under the crystalline and amorphous portions was determined in arbitrary units and the degree of crystallinity (Dc) was calculated using the relation [9]. ...
... where Ia and Ic are the integrated intensity corresponding to amorphous and crystalline phases, respectively. Also, the grain size (t), interchain distance (r), interplanar distance (d) and distortion parameter (lattice strain) (g) were calculated as follows [9][10][11]: ...
Nanostructured ZnO powder was synthesised by a simple chemical route. The material was characterised by XRD, UV, SEM and TEM techniques. XRD and TEM studies confirm that a nanostructured ZnO is obtained by using simple chemical route. The nanopowder was fired at an optimised temperature of 200°C for 1/2 h. The prepared powder had crystallite size in the range from 19 to 41 nm. Thick films of synthesised ZnO powder were prepared by screen printing technique. The gas sensing performances of these films for various gases were tested. Films showed highest response to H 2 S (100 ppm) gas at 300°C temperature with poor responses to others. The quick response and fast recovery are the main features of this sensor. The effects of microstructure, operating temperature and gas concentration on the gas response, selectivity, response time and recovery time of the sensor in the presence of H 2 S gas and others were studied and discussed.
... The study of the electron beam effects on EVA, including the electron beam modification of EVA is already a classical area of work [100][101][102][103][104], in contrast to the more recent research area of the microwave effect on EVA [105]. As in the previously mentioned research trends, EVA copolymers [106][107][108][109][110] and blends were initially investigated (and, accordingly, electron beaminduced cross linking [111][112][113], interest in which has been renewed in the 21 st century [114][115][116][117]), then the research focus was moved to EVA composites and, in particular, nanocomposites (including clay filled or mineral fiber reinforced ones) [118][119][120][121][122][123]. Interest in EVA-containing polymer blends remains due to the technological optimality of the electron beam irradiation induced compatibilization [124] and the multifactor nature of the irradiation effect observed [125][126][127]. ...
Manuscript submitted to MSF post-conference publication (full version: 41 p.): Jun 7, 2022. Manuscript ID: 0030. Registration date: Jun 14, 2022. Revised (truncated) version: Aug 18, 2022. Accepted: Aug 22, 2022. Rejcted for publication by Trans Tech Publication by a regional office in Dnipro city (due to the international sanctions against Russian Federation): Feb 9, 2023.
... The study of the electron beam effects on EVA, including the electron beam modification of EVA is already a classical area of work [100][101][102][103][104], in contrast to the more recent research area of the microwave effect on EVA [105]. As in the previously mentioned research trends, EVA copolymers [106][107][108][109][110] and blends were initially investigated (and, accordingly, electron beaminduced cross linking [111][112][113], interest in which has been renewed in the 21 st century [114][115][116][117]), then the research focus was moved to EVA composites and, in particular, nanocomposites (including clay filled or mineral fiber reinforced ones) [118][119][120][121][122][123]. Interest in EVA-containing polymer blends remains due to the technological optimality of the electron beam irradiation induced compatibilization [124] and the multifactor nature of the irradiation effect observed [125][126][127]. ...
The article begins with a comprehensive review of the topic of EVA-containing polymer composites for tissue engineering on ethylene-vinyl acetate copolymer-based systems. The article focuses on the problem of textural and (bio)chemical biocompatibility of the material. As a solution to the first problem, it is proposed to use electron microscopy and correlation spectral image analysis, which emulates laser diffraction (2D FFT implemented with the FFTW library in QAVIS software). The article also describes the modernization and digitization of an electron microscope, thanks to which such analysis becomes possible in a video stream and in real time or post factum. Also, eleven tables of analysis results are given so that each specialist in the field of cell biology and regenerative medicine can independently assess the suitability of certain polymer compositions with different ratios of components for his tasks.
... In the region of 500-600 cm −1 , a band of multiple peaks resulting from oxidative deterioration due to gamma irradiation occurs. CO stretching and OH bending are thought to be responsible for this band [31]. Another peak appeared around 1750 cm −1 after irradiation, and its intensity increased as the radiation dose increased. ...
PLA and its nanocomposite containing 3% chitosan nanoparticles (PLA-3CsNP) were studied to see how γ-irradiation affected their characteristics. Different doses of γ-irradiation were applied to the investigated materials under inquiry (5-40 kGy) using 60 Co at ambient conditions. The irradiation materials were characterized by FT-IR, GPC, mechanical tensile test, DSC, XRD, and TGA in solid and chloroform solutions. The molecular weight of the studied materials was lowered when the irradiation dose was increased, indicating that γ-irradiation had the dominating effect through oxidative degradation, and chain scission. The addition of chitosan to PLA reduces the impact of γ-irradiation, while the samples irradiated in solution showed more degradation after irradiation than irradiated solid films. Irradiation caused a decrease in tensile strength and elongation at break values. Both the melting temperature (Tm) and the glass transition temperature (Tg) decreased as the irradiation dose was increased. The crystallization peak temperatures were reduced when pure PLA was irradiated in solution. The thermal stability of PLA was diminished as the irradiation dose was raised, and this effect was more pronounced in samples irradiated in chloroform solution.
... These peaks are the consequence of gamma-irradiation-induced oxidative damage. These peaks are believed to be caused by OH bending [38]. Otherwise, some of the detected peaks were reduced after irradiation of PVC films. ...
This study aims to provide more information about the gamma radiation effects on the PVC films used for the production of
urine and drainage bags (medical products). The PVC films were irradiated by gamma radiation using different doses namely,
20, 40, 60, 80, 80, 100, 120, and 140 kGy. The gamma radiation effects on the unirradiated and irradiated PVC films were
examined using FTIR, XRD, TGA, DSC, SEM, EDX, and mechanical properties. In conclusion, the results showed that
the physicochemical properties of PVC films were affected by the standard gamma radiation dose of sterilization (20 kGy).
... In the region of 500-600 cm −1 , a band of multiple peaks resulting from oxidative deterioration due to gamma irradiation occurs. CO stretching and OH bending are thought to be responsible for this band [31]. Another peak appeared around 1750 cm −1 after irradiation, and its intensity increased as the radiation dose increased. ...
PLA and its nanocomposite containing 3% chitosan nanoparticles (PLA-3CsNP) were studied to see how γ -irradiation affected their characteristics. Different doses of γ -irradiation were applied to the investigated materials under inquiry (5–40 kGy) using ⁶⁰ Co at ambient conditions. The irradiation materials were characterized by FT-IR, GPC, mechanical tensile test, DSC, XRD, and TGA in solid and chloroform solutions. The molecular weight of the studied materials was lowered when the irradiation dose was increased, indicating that γ-irradiation had the dominating effect through oxidative degradation, and chain scission. The addition of chitosan to PLA reduces the impact of γ-irradiation, while the samples irradiated in solution showed more degradation after irradiation than irradiated solid films. Irradiation caused a decrease in tensile strength and elongation at break values. Both the melting temperature (Tm) and the glass transition temperature (Tg) decreased as the irradiation dose was increased. The crystallization peak temperatures were reduced when pure PLA was irradiated in solution. The thermal stability of PLA was diminished as the irradiation dose was raised, and this effect was more pronounced in samples irradiated in chloroform solution.
... In the region of 500-600 cm − 1 , a band of multiple peaks resulting from oxidative deterioration due to gamma irradiation occurs. CO stretching and OH bending are thought to be responsible for this band (Chattopadhyay et al. 2001). Another peak appeared around1750 cm − 1 after irradiation, and its intensity increased as the radiation dose increased. ...
PLA and its nanocomposite containing 3% chitosan nanoparticles (PLA-3CsNP) were studied to see how γ -irradiation affected their characteristics. Different doses of γ -irradiation were applied to the investigated materials under inquiry (5–40 kGy) using ⁶⁰ Co at ambient condition. The irradiation materials were characterized by FT-IR, GPC, mechanical tensile test, DSC, XRD, and TGA in solid and chloroform solutions. The molecular weight of the studied materials was lowered when the irradiation dose was increased, indicating that γ-irradiation had the dominating effect through oxidative degradation, and chain scission. The addition of chitosan to PLA reduces the impact of γ-irradiation, while the samples irradiated in solution showed more degradation after irradiation than irradiated solid films. Irradiation caused a decrease in tensile strength and elongation at break values. Both the melting temperature (Tm) and the glass transition temperature (Tg) decreased as the irradiation dose was increased. The cold crystallization peak temperatures were reduced when pure PLA was irradiated in solution. The thermal stability of PLA was diminished as the irradiation dose was raised, and this effect was more pronounced in samples irradiated in chloroform solution.
... The band around 1238 cm −1 is assigned to the asymmetric C-O-C deformation in the acetate group, while at 1022 cm −1 it is associated with the symmetric C-O-C group of the acetate. The bands at 720 cm −1 and 610 cm −1 are characteristic of the vibration of groups CH 2 and C=O [41,42], respectively. However, the chemical modification process of EVA using maleic anhydride, dicumyl peroxide and the styrene monomer promoted the appearance of new bands in the FTIR spectrum, as seen in Fig. 3. Figure 3 illustrates the expanded region of FTIR spectrum of the neat EVA and EVA-g-MA, in the range from 1825 to 1750 cm −1 . ...
The functionalization of the ethylene–vinyl acetate copolymer (EVA) was carried out in an internal mixer, using maleic anhydride (MA), dicumyl peroxide (DCP) and styrene monomer (St) as additives. Torque rheometry, Fourier transform infrared spectroscopy (FTIR), titration, gel content, thermogravimetry (TG) and differential scanning calorimetry (DSC) were evaluated. The EVA/MA/DCP and EVA/MA/DCP/St torque curves showed a significant increase, indicating the cross-linking process. FTIR confirmed the appearance of a new band in the EVA chain, at 1780 cm−1, attributed to the carbonyl group of maleic anhydride. However, maleic anhydride grafting to the EVA/MA/DCP system only occurred for the 5% MA/0.3% DCP ratio. When the EVA/MA/DCP system is additivation with the styrene monomer (St), all compositions grafted maleic anhydride into the EVA chain, suggesting that styrene increases the effectiveness of the degree of grafting. In addition, FTIR indicated the emergence of a band at 702 cm−1, due to the vibration of the aromatic core of styrene and, therefore, forming a multiphase copolymer (EVA-g-(St-co-MA)). The thermal stability was practically not altered when functionalizing the EVA with maleic anhydride, as verified by TG. The crystalline melting temperature, the crystallization temperature, the enthalpy of crystalline melting and the degree of crystallinity decreased with the EVA functionalization process. In general, a high degree of grafting of maleic anhydride in the EVA chain is difficult, due to the competitive effect with the cross-linking process.
... It is essential that in a continuous plastic phase, the rubber phase should be dispersed uniformly, and the finer the dispersed phase the better are the properties. A number of TPEs from dynamically vulcanized rubber-plastic blends have been developed by Bhowmick and coworkers [98][99][100][101][102]. ...
... Therefore, with increasing alpha fluences the intensities of irradiated Table 3. This disorder structure can be attributed to the cross linking that causes a reduction in the crystalline structure [41]. Also, it can be explained by the formation of new bonds between the neighboring chains causes a change in the regularity of the arrangement of the crystallites into disorder as a consequence of the molecular chains cross-linking. ...
Cellulose Nitrate (CN-85) polymer samples were irradiated by alpha particles with different fluences varying from 1.45 × 10⁶ to 7.2 × 10⁶ particles/cm² using a ²⁴¹Am source. The optical and structural alterations produced in CN-85 nuclear track detector (NTD) by alpha particles were studied using Ultraviolet-visible, photoluminescence spectroscopy and X-ray diffraction techniques. The results of UV–VIS analysis demonstrate that the transmittance diminishes as the fluences of alpha particle increase. The effect of alpha irradiation on direct and indirect optical band energy gap (Eg) was observed, and the Urbach's energy (Eu) calculations reveal a reverse linear relation between Eu and Eg. The integrated intensity (I) under the PL spectra exhibits a linear relation with the alpha-particle fluences through the specified range of fluences. This linear relation gives the possibility to use the CN-85 detector for alpha particle detection using photoluminescence spectroscopy. X-ray diffraction of the irradiated CN-85 samples show a broadening in the FWHM of diffracted peak and this is due to the decrease in the crystallite size that indicates the dominant of disorder atomic structure in alpha irradiated samples. The obtained results show an improvement in the studied properties of the CN-85 polymer after irradiated with the alpha particles.
... It was discovered that the crystalline phase of the blends is affected by electron-beam radiation only at higher doses (200 kGy and above), the gel fraction increases with increases of the radiation dose, and the ethylene-vinyl acetate and ditrimethylol propane tetraacrylate content. The morphology of blends does not change after irradiation [2,3]. ...
Some polymers need a cross-linking agent for the controlled cross-linking process of polymers with a tendency to degradation during the radiation cross-linking process. While, on the other hand, other polymers do not need a cross-linking agent—predominantly there are cross-linking polymers. The Thermo-Plastic Elastomer (TPE) that was used belongs to this group of predominantly cross-linking polymers; however, this agent is added because of faster reaction times and smaller irradiation doses. Microindentation–tensile and tensile impact tests were carried out on a thermoplastic sample—with, and without, a cross-linking agent. Small changes were measured between these materials at low radiation doses, (up to 66 kGy); nevertheless, at higher doses, the influence of the cross-linking agent on the mechanical properties is significant.
... From these spectra show that the XRD patterns of CNT at the angular (2θ) of 42°, 62° and 76° are shown at figure 3.3a of polystyrene-acrylonitrile-CNT in the same angular (2θ) and not appear at figure-3b of polystyrene-acrylonitrile. These peaks are well characterized in grafted polymer and correspond to specific crystallographic planes 10 . The intensity of the crystalline peaks of grafted polymer is high and sharp. ...
Acrylonitrile was successfully grafted on polystyrene modified with carbon nanotubes using gamma-irradiation technique. This
process was carried out at various gamma doses (0.2-1.5 Mrad). The new grafted polymer (GP) was characterized and its
properties were investigated. In this study, it was found that 2 gm of polystyrene, 90% (w/w) acrylonitrile monomer, 2% (w/w)
ferrous ammonium sulfate (FAS) catalyst, 1 mg carbon nanotubes powder and 1.25 Mrad gamma dose are the optimum
conditions required for the polymerization of GP. The grafted polymer was proved true by Fourier transform infrared
spectroscopy (FTIR), UV-Visible spectroscopy and XRD. A mechanism is presented to explain the formation of GP modified
with carbon nanotubes.
... While the chief difficulty opposite us during synthesizing a graft copolymers reaction, is the lack of commercial methods of synthesis and lower present graft yield. It is well known that, the most significant methods of synthesis involve the employ of chemical free radical initiator i.e. conventional method [13][14][15][16] high energy radiations i.e. gamma and X-ray, UV-radiation based method, and recently the microwave based methods [17][18][19][20]. The conventional (physical method) process of grafting uses a chemical free radical initiator to generate a steady distribution of the free radical sites on the polymer backbone, where the monomer of the graft gets added up to form the graft chain. ...
Polysaccharides are bio-degradable, inexpensive and easily available from consistent agricultural resources. Polysaccharides and their derivatives represent a group of polymer widely used in pharmaceutical and biomedical fields. The biodegradability of natural polymers reduces their shelf life. Grafting copolymerization technique is a most effective fascinating way for chemical modification of native characteristics of polysaccharides with maximum possibilities for improving the properties of polysaccharides and enhanced the range of exploitation. While the major difficulty facing us during synthesizing a graft copolymers reaction, is the lack of commercial methods of synthesis and lower percent graft yield. It is well known that, the most important methods of synthesis engage the employ of chemical free radical initiator i.e. conventional based methods. Graft copolymerization through γ-radiation method is a better method of grafting in comparison to chemical method and exhibits a great potential to synthesize the graft copolymers by virtue of its higher efficiency, low cost, higher thermal stability as well as enhanced the yield of graft copolymer. Future prospective of irradiation technique would be significant impacts to develop of polymerization.
... Interplanar distance d was determined using Bragg's condition 2dsin = n . Degree of crystallinity [19], grain size, interplanar distance, average texture coefficient, dislocation density, lattice strain etc. were also determined using the relations (eq.1-7) [20][21][22] and systematically tabulated in Table 2. ...
Nanocrystalline SnO2 thin films were successfully prepared using Physical Vapour Deposition technique and were annealed at 400oC. Structural, morphological, elemental, compositional, optical, and electrical and gas sensing properties were studied using XRD, FESEM, EDXS, UV-Vis Spectrophotometer, DC resistance measurement method respectively. Acetone, Cl2, CO2, Ethanol, H2S and NH3 sensing performance of Nanocrystalline physically vaporized SnO2 thin films were investigated and reported in this paper. The results were systematically tabulated, interpreted and discussed.
Keywords: SnO2 thin film, PVD technique, XRD, FESEM, gas sensor, sensitivity.
... It has been found that the decreases the peak intensities usually related to the deceases the crystallinity of materials. Furthermore, interplanar distance (d), interchain distance (r), micro strain (), and distortion parameter (g) were calculated as follows [35][36][37][38]. Table 1shows the different XRD parameters for all the samples. ...
A systematic investigation on the synthesis, characterization, optical and magnetic
properties of (Co-Mn) co doped ZnO nanoparticles synthesized by sol-gel method is
reported. Structural, Optical and magnetic properties of present sample have been
characterized by X-ray diffraction (XRD), UV-VIS-NIR spectroscopy and VSM techniques. The
single- phased wurtzite structure has been confirmed by XRD analysis. The nanoparticles
nature of the samples and their crystallinity has been investigated by TEM measurements.
Optical studies revealed red shift (3.315–3.289 eV) with increasing Mn doping
concentration in the absorbance spectrum. Magnetization studies showed that
Zn0.7Co0.2Mn0.1O exhibits ferromagnetic behavior.
Graphical abstract
... These difficulties in the preparation of film samples for SEM or TEM show the main advantage of AFM, in which the sample can be used without any preparation. Although previous research has combined chemical etching of sample surfaces with AFM observation [7,14], the challenge of AFM is to obtain topographical and microstructural information while avoiding the use of specific etching or washing. ...
Atomic force microscopy (AFM) has been used for the characterization of the surface topography and microstructure of polyethylene (PE) films with thickness of about 50 μm. Different compositions of the films were tested, including mixtures of LDPE fabricated with metallocene polyethylene (mPE). The characteristics of the fibrils and spherulites of the films have been observed by means of AFM without any preparation of the samples, allowing also differentiation of the amorphous and crystalline zones. A method is proposed for the quantification of the proportion of crystallinity based on the roughness of the films.
This work aimed to develop compatible blend between natural rubber (NR) and ethylene propylene diene rubber waste (w-EPDM). This was done by introducing third rubber matrix and electron-beam (EB) irradiation. As for the first method, natural rubber latex (NRL) was added where it was mixed with w-EPDM prior to blend with NRL on a two-roll mill. However, the latter route was prepared differently, EB-exposed to the samples in the presence of trimethylolpropane triacrylate (TMPTA) as cross-linking promoter. By applying these two methods, the compatible blends of NR and w-EPDM were successfully prepared. The blends exhibited good cure properties, solvent resistance, tensile, and dynamic mechanical properties. NR and w-EPDM were more entangled after introducing these two methods.
For the last couple of decades, high-energy electron beam radiation is being used for cross-linking and curing polymers and polymer blends. Thermoplastic elastomers (TPEs) blends are gaining importance in recent years because they offer several practical advantages over thermoset rubbers (cross-linked). They show higher mechanical properties than vulcanized rubber but can be rapidly processed and fabricated like thermoplastics. This chapter includes the effect of electron beam radiation on various properties of a series of thermoplastic elastomeric blends such as EPDM-PP, EPDM-PE, NBR-PP, and NBR-PE. The role of the electron beam in controlling various properties of EPDM, PP, PE, and NBR is discussed in this chapter. This chapter also discusses the EB-assisted preparation of thermoplastic elastomer blends. It is observed that up to a certain dose of EB encourages cross-linking leading to various useful properties. If dose is very high depending on the systems, the degradation starts deteriorating the properties. The structure–property relationship has been established for every system. Overall, the chapter is providing information on the preparation, modification of properties, and possible applications of various thermoplastic elastomer blends.
Radiation processing is an excellent commercially viable technology to improve various properties of polymeric products in a solid state without using chemical catalysts at room temperature. Thermoplastic elastomers (TPEs) possess some disadvantages like poor set and chemical/oil resistance as compared to a crosslinked elastomer which can be significantly improved by the ‘dynamic vulcanization process’. But it imparts compounding complexity and trims down the purity of the TPE systems. In this regard, electron beam (EB) modification of these blends at a controlled radiation dose is one of the best alternatives. To widen the diversity of polymers, another well-known approach is to modify their technical properties by the addition of nanofillers. Controlled irradiation can potentially be an effective way of tailoring the technical properties of such polymeric nanocomposites. This chapter aims to explore some expected and unexpected achievements in recent developments of the radiation processed hybrid organic–inorganic polymer nanocomposites based on a nanosilica-reinforced (LDPE/EVA) TPE system. A brief overview of the simultaneous effect of nanosilica and controlled EB irradiation on the mechanical, rheological, thermal, and electrical properties of this model system is outlined which will help to give valuable insights into new research directions. This green technique studied can be potentially extended for the improvement of the technical properties of conventional TPE systems.KeywordsRadiation crosslinkingTPEPolymer nanocompositesSilica nanoparticleDispersionsReinforcement
Impedance spectroscopy analysis has been employed to investigate the effect of melt mixing time on electrical conduction mechanism, direct contact or electron tunneling, of a polymer blend using a conductive masterbatch. A novel approach is proposed to correlate the dispersion/distribution states of conductive nanoparticles within the phases, achieved through kinetic control of the conductive masterbatch, and their impedance properties. A blend of polypropylene and ethylene-vinyl acetate copolymer (PP/EVA) was considered as a case study for the matrix. An electrically conductive masterbatch of multiwalled carbon nanotubes (MWCNTs) in polypropylene-grafted-maleic anhydride (PP-g-MA) was added to the blend. The masterbatch in varying amounts was mixed with PP/EVA in a range of 1 min–4.5 min. The co-continuous morphology of the ternary polymer blend was validated via scanning electron microscopy micrographs. The atomic force microscopy (AFM) results showed that as the mixing time of the masterbatch increases the interconnected structures within the conductive interphase decrease. Impedance spectroscopy using alternating current was employed to probe the conduction mechanism in the composite blends. The impedance spectroscopy results revealed that for samples with low mixing time, a dielectric relaxation peak occurs at high frequencies due to the existence of more conductive pathways as a consequence of the interconnected structures of the masterbatch phase. Also, the major contribution of conductance was direct contact in the samples with low mixing times while electron tunneling mechanism was considerable for the samples with high mixing times. Dielectric constant was increased as a result of interfacial polarization boosting with mixing time. The percolation threshold was considerably decreased from 0.95 v% for simultaneous direct mixing method to 0.16 v% for the masterbatch method.
The effects of electron beam (EB) radiation in thermoplastic elastomers based on SEBS/TPU and SEBS‐g‐MA/TPU are evaluated. 60/40 blend of both the systems were subjected to EB using an ILU type industrial accelerator. Radiation dose was varied from 0 to 100 kGy, and the sol–gel content evaluation along with detailed analysis of mechanical, thermal, rheological, and morphological implications was conducted. The interplay between crosslinking and chain scission was quantified using the Charlesby‐Pinner equation. Both the blends showed the presence of a three‐dimensional cross‐linked network in them after the irradiation. The tensile strength of SEBS/TPU was found to deteriorate with an increase in radiation dose, but an opposite trend was observed in SEBS‐g‐MA/TPU. Improvement in interfacial adhesion between SEBS‐g‐MA and TPU was confirmed. The morphological analysis through atomic force microscopy and scanning electron microscopy clearly showed the appearance of rough ridges and pits due to irradiation along with the cross‐linked networks. From differential scanning calorimetry analysis, the changes in glass transitions and melting endotherm were assessed. Thermogravimetric analysis results indicated an improvement in the thermal stability of the blends. The storage modulus and complex viscosity of the samples enhanced as perceived from the rheological measurements. X‐ray diffraction patterns of the blends also showed considerable variation after irradiation.
Nowadays, ion bombardment became one of the powerful methods usually carried out to modify the surface characteristics of the polymeric materials. In this work, low-density polyethylene (LDPE) polymer samples were bombarded with different fluences by 130 keV He-ion beam. The X-ray diffraction patterns of the untreated sample as well as those exposed to He-ion beam revealed the crystalline nature of the samples. The effects of He-ion beam bombardment on the structural parameters e.g. crystal size, dislocation density, inter-chain separation, micro-strain, and distortion were studied. The optical absorption coefficient and refractive index were calculated as a function of He-ion beam fluences. The optical energy gap and Urbach energy were also evaluated. Wemple-DiDomenico effective single oscillator and Sellmeier models were both used to describe adequately the refractive index dispersion in the low absorption region. Graphical representation of the complex dielectric constant and dissipation factor was also presented. A significant modification in the structural and optical parameters was obtained by ion bombardment technique.
Graphene nanoplatelets (GnP) and α-MnO2 decorated GnP were integrated into an ethylene vinyl acetate (EVA) matrix using the dual mixing method (solution followed by melt mixing). GnP was added in 1, 3, 5, 8, 10 and 15 phr loadings into an EVA matrix to obtain composites and evaluate their various properties suitable for mechanical and electrical applications. The graphene nanoplatelets were further decorated with α-MnO2 which was subsequently integrated into EVA at an 8 phr loading to form composites. It was observed in the GnP-EVA composites, that with an increasing GnP content, a substantial increase in the tensile strength (188%) over the neat polymer was observed at a 10 phr loading but reduced thereafter at a 15 phr loading. Dielectric permittivity of the composites were observed to increase with an increasing filler loading, the addition of α-MnO2 also having a beneficial effect. Conductivity as well as the electromagnetic interference shielding performance were improved with increasing GnP concentrations. A maximum 28 dB of shielding was observed in the 15 phr loaded GnP-EVA composite whereas the α-MnO2 decorated GnP-EVA composite showed a shielding efficiency of 22 dB at a concentration of 8 phr for a thickness of 2 mm with excellent thermal and mechanical properties. Overall, the composite material will find its application as a flexible EMI shielding material.
Heterogeneous blends of millable polyurethane (MPU) and ethylene-co-vinyl acetate (EVA) elastomers have been prepared by conventional open mill mixing, and subsequently cured with DCP as curing agent. The prepared blends were characterized by TGA, DSC, XRD and DMA techniques. Mechanical and solvent transport features have been evaluated. Examination of EVA phase crystallization dynamics revealed that the 50:50 blend possessed a higher energy barrier during crystallization. When EVA became the minor or major phase, the system offers similar energy barrier features. Solvent transport mechanism has been found to shift towards non-Fickian for blends with EVA as the major phase. Mechanical properties have been found to be complementary to the observed crystalline features of the blends. A blend with EVA to MPU ratio 80:20 is highlighted as a soft and strong material, with enhanced solvent resistance features suitable as a matrix for different engineering applications.
Development of MPU/EVA blends
Ethylene vinyl acetate/Thermoplastic polyurethane/Layered double hydroxide (EVA/TPU/LDH) nanocomposites were prepared with varying LDH content via melt mixing technique. The nanocomposites show significant improvement in tensile strength and modulus and the optimum improvement was obtained for E70L3 containing 3 wt% LDH. X-ray diffraction study (XRD) suggested the possible crystal disordering and partial exfoliation of LDH layers in the matrix and this exfoliation is also supported by transmission electron microscopy (TEM) study. Dynamic mechanical thermal analysis shows that the storage moduli of the nanocomposites are higher as compared to the unfilled blend. FTIR study also depicts the interaction between the polymer matrix and nanofiller. Thermogravimetric analysis indicates the better thermal stability and higher char residue for the exfoliated nanocomposites. The presence of the LDH positively affects the flame retardance characteristics with a steady increase in limiting oxygen index (LOI) value. Melt rheological analysis exhibits significant changes in the value of relaxation exponent and shear thinning exponent for the nanocomposites as compared to the neat blend. Thus, LDH turn out to be an excellent multifunctional additive for this blend system.
Reactive blending has been carried out by the melt mixing of linear low density polyethylene (LLDPE) and silicone rubber containing vinyl group (PMVS) to obtain grafted and crosslinked blends. Two methods involving the use of free radicals generated from (a) thermomechanical shear and (b) peroxide decomposition were used to prepare the LLDPE/PMVS blends. The occurrence of grafting and crosslinking of the PMVS molecular chains was deduced by considering the mixing torque, solvent extraction data and evidence from the Fourier transform infrared spectra (FTIR), as well as differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The experimental results indicated that reactive blending significantly improved the interfacial adhesion between the two phases and that peroxide decomposition had a higher initiation efficiency in respect of grafting and crosslinking than thermomechanical shear.
Thermogravimetric analysis (TGA) showed that reactive blending with PMVS improved the thermal stability of LLDPE. Dynamic rheological behaviour and melt flow rate (MFR) results suggested that grafting and crosslinking between the two components increased the viscoelasticity of the blends and the addition of PMVS improved the processability of the LLDPE.
Crosslinking by peroxides gave a higher tensile strength than thermomechanical shear but a lower elongation at break. The limiting oxygen index (LOI) test indicated that the flame retardancy of the LLDPE/PMVS blend increased with increasing amounts of PMVS.
A series of ethylene vinyl acetate (EVA)/ethylene-propylene diene elastomer (EPDM) blends (50/50 ratio) with four types of EVAs were prepared using brabender type batch mixer followed by compression molding. All compression-molded samples were exposed to gamma radiation at 500, 1000, and 1500 kGy doses and were subjected to mechanical, compression set, thermal and morphological test. The % retention in tensile strength, elongation, and hardness were found higher for higher vinyl acetate (VA) containing radiation aged EVA/EPDM blends. The compression set value was decreased with increase of VA content. The thermal degradation kinetics of high VA containing irradiated blend (EVA40/EPDM) (EVA40 is 40%VA containing EVA) was found slower than those of lower VA containing blend (EVA18/EPDM). The surface morphology for EVA18/EPDM sample was transformed into more irregular one with more cracks and fragmented segments by aging at 1500 kGy dose while surface for EVA40/EPDM sample was found comparatively smooth, fine, and continuous with very few cracks and fragmented parts at similar dose. Thus, from the measured properties and morphology, it was revealed that the degree of degradation of blends kept on decreasing with increase in VA content. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 136, 46216.
In the present investigation, high density polyethylene (HDPE) polymer has been used to study the alterations in its properties under gamma-irradiation. Physico-chemical properties have been investigated with different spectroscopy techniques, Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD), biocompatibility properties, as well as, mechanical properties change. The FT-IR analysis shows the formation of new band at 1716 cm⁻¹ that is attributed to the oxidation of irradiated polymer chains, which is due to the formation of carbonyl groups (C=O). XRD patterns show that a decrease in the crystallite size and increase in the Full Width at Half Maximum (FWHM). This means that the crystallinity of irradiated samples is decreased with increase in gamma dose. The contact angle measurements show an increase in the surface free energy as the gamma irradiation increases. The measurements of mechanical properties of irradiated HDPE samples were discussed.
A novel thermoplastic vulcanizate (TPV) based on the blends of ethylene vinyl acetate/thermoplastic polyurethane (EVA/TPU) at various blend ratios has been developed via dynamic vulcanization at 180°C using di-(2-tert-butyl peroxy isopropyl) benzene (DTBPIB) peroxide as the cross-linking agent. Modification of the EVA/TPU blends via dynamic crosslinking significantly improves the tensile strength and modulus of the system and the improvement is more significant for EVA/TPU 50/50 and 60/40 blends. AFM study shows that crosslinked EVA particles are dispersed in the continuous TPU matrix and the dispersed EVA domain sizes are relatively smaller in EVA/TPU 50/50 and 60/40 blends leading to good mechanical properties. FTIR spectroscopy has been used to characterize the specific chemical changes occurring due to dynamic vulcanization. This TPV has excellent retention of physico-mechanical properties even after reprocessing twice and the blends also have very good thermal resistance as indicated by aging study. The samples were found to exhibit remarkable improvement in oil resistance property as compared to their uncrosslinked counterpart. The creep behavior of the blends significantly improves after dynamic crosslinking and blends with higher TPU content show better creep resistance. Volume resistivity of all the peroxide vulcanized blends is in the range of 1013 ohm cm, which is suitable for cable sheathing application.
The chapter provides introduction to radiation processing of solid state materials, using commercially available sources of ionizing radiation, i.e., radio-isotopic and/or accelerated electron beam installations. Dosimetry is described as the method of controlling progress of changes in irradiated material. Distribution of doses in irradiated material is described, allowing proper processing of polymers. Basics of radiation chemistry of polymers is explained, in particular of elastomers. Radiation-induced crosslinking is most interesting reaction, but it can be accompanied by undesired phenomena like chain scission. Specific phenomena like energy transfer occur in radiation processing; therefore, composites of elastomers with components of different radiation characteristics may show unexpected results. Examples of selected cases are described in details. Comparisons between traditional methods of crosslinking with these using ionizing radiation allow consideration of introduction of the latter into industrial praxis.
Most rubber materials are subjected to oxidation. The rate of oxidation depends on the type of rubber, processing method, and end-use conditions. The oxidation of rubber can result in the loss of physical properties, such as tensile strength, elongation, and flexibility. Hence, the service life is determined by oxidation stability. Thermal properties are relevant to the potential use of polymeric materials in many consumer oriented applications. Thermo-oxidative ageing and thermogravimetric analysis (TGA) have been proven to be successful techniques in determining the thermal stability of polymers and polymer blends. In this article, preparation of a series of natural rubber/recycled ethylene-propylene-diene rubber (NR/R-EPDM) blends is described. Processing of the blends, by means of introducing pre-vulcanised EPDM and electron beam (EB) irradiation, was carried out. Two thermal analysis methods, namely thermo-oxidative ageing and thermogravimetric analysis, were conducted. The results indicated that pre-vulcanising EPDM for 1.45min (ts - 2) is sufficient to gain the optimum retained tensile and elongation at break. It was simultaneously observed that the introduction of pre-vulcanised EPDM increased decomposition temperature and activation energy by showing optimum values at a pre-vulcanising time of 3.45 min (ts). In the latter study, the retained properties increased after EB irradiation. The results can be verified by the thermal decomposition temperature and their activation energy. The obtained TG profiles and the calculated kinetic parameters indicated that introducing EB irradiation into the blends enhanced their thermal stability. The thermal stability of the blends, processed by these two means, is significantly enhanced; irrespective of pre-vulcanising time or irradiation dose.
The effects of electron beam radiation (EBR) on the blends of Ethylene vinyl acetate/Thermoplastic Polyurethane (EVA/TPU) at two different blend ratios prepared via melt blending technique were investigated. All the samples were irradiated by using a 2.5 MeV electron beam accelerating energy over a dose range from 25 to 200 kGy. The blends exhibit drastic improvement in the mechanical properties with increasing radiation dose upto an optimum dosage, beyond which the properties began to deteriorate. Modification of the blends via EBR enhances the elastic recovery of the blends resulting significant improvement in tension set behaviour. DSC study shows that electron beam irradiation causes a marginal change in melting temperature (Tm), glass transition temperature (Tg) and crystallization peak temperature (Tc) of EVA/TPU blends. Dynamic mechanical analysis (DMA) was conducted to investigate the change of loss tangent and storage modulus with varying radiation dose. Thermogravimetric analysis (TGA) suggests that irradiation induced crosslinks also help to improve the thermal stability of the blends to some extent. Scanning electron microscopy (SEM) study was performed to explore the changes in morphology before and after irradiation. All the irradiated blends have higher electrical resistivity than the blends without irradiation and the volume resistivity increases upto 150 kGy. The samples were found to exhibit remarkable improvement in oil resistance property after irradiation which is more prominent in EVA/TPU 70/30 blends.
The optical and structural response of low density polyethylene (LDPE) under the influence of 80 MeV N6+
ion at various fluences (5 1011 to 1 1013 ions/cm2
) and gamma rays at doses 100 and 1000 kGy were
studied using UV–Vis spectroscopy and X-ray diffraction (XRD). The optical absorption spectra of N6+ ion
irradiated LDPE showed a shift in the absorption edge towards higher wavelength side, which indicated a
significant decrease in the direct and indirect band gaps of the films. The optical data showed decrease in
the calculated band gap with increasing gamma dose. The diffraction pattern of pristine sample showed
the semi crystalline nature of the polymer. The decrease in peak intensity and hence increase in amorphous
nature was observed in N6+ ion irradiated samples. The opposite behavior is seen in case of gamma
ray exposed samples at 100 kGy dose. The crystallite size (L) decreased but the other factors like interchain
separation (R), interplanar distance (d), micro strain (e), dislocation density (d) and distortion
parameters (g) increased for N6+ ion irradiated samples.
Ethylene vinyl acetate (EVA) copolymer and thermoplastic polyurethane (TPU) with different blending ratios were melt mixed in an internal mixer. The blends were then exposed to electron beam (EB) irradiation with different doses of 50, 100, 150, 200 and 250 kGy. FTIR spectroscopy and dynamic mechanical thermal analysis (DMTA) were used to investigate the effect of cross-linking and blending ratio on chemical structure as well as solid state viscoelastic properties of the blends. FTIR spectroscopy showed interchain cross-linking during melt blending and also radiation cross-linking during solid state irradiation. Observation of one damping peak for blends at almost all blending ratios was an indication of miscibility of these blends. The results indicated formation of interchain cross-linking stabilised with exposure to EB irradiation. Mechanical properties of the blends were investigated via stress–strain curves. Modulus showed a monotonic increasing trend with the radiation dose, but tensile strength and elongation at break were initially increased and then decreased with increasing radiation dose. This was attributed to two competing parallel factors of strain induced crystallisation and degree of cross-linking.
Electron beam crosslinked EVA/SMR L/organoclay nanocomposites had been produced by using a crosslink promoter, TMPTA. The EVA to SMR L ratio was fixed at 50:50 and the organoclay loading used was 2 phr and 8 phr. When the nanocomposites were irradiated up to 200 kGy without TMPTA, the gel fraction was below 55%, but with addition of 3 phr TMPTA the gel fraction increased to 80%. Different level of irradiation dose also was found to form different phase morphology on the nanocomposites as shown in the SEM micrographs. Analysis on FT-IR spectrum proved that the addition of TMPTA improved the crosslinking and grafting, whereas incorporation of organoclay reduces oxidative degradation of the nanocomposites. DMA analysis showed that both storage modulus and glass transition values increased with addition of TMPTA at all irradiation doses. However, the improvement of thermal decomposition temperatures of nanocomposites with TMPTA were lower compared to non-irradiated nanocomposites.
Thermosets obtained by reacting highly functionalized maleic anhydride-grafted polyethylene and a polyetherdiamine at several NH2/MA molar ratios were characterized for their gel content, thermal, mechanical, and thermo-mechanical behavior. Gel content varied with composition and a maximum (57%) observed when NH2/MA molar ratio was 1.5. Two melting transitions were observed for thermosets, representing the semicrystalline polyethylene fraction in the gel and sol part of the material in contrast to a single transition for the starting polyethylene. Overall crosslinking suppressed the crystallinity of the polyethylene in the thermoset. A single Tg observed in the DMA analysis suggested phase mixing between the polyethylene and polyether chains. A shift in the Tg observed was related to the degree of crosslinking in the thermosets. Tensile properties of the thermosets were observed to be a strong function of composition and the degree of crosslinking and the optimum mechanical performance was shown by thermosets when NH2/MA molar ratio was 1.5 and 2.0. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Mechanical and dynamic mechanical properties of natural rubber/recycled ethylene-propylene-diene rubber (NR/R-EPDM) blends were simultanoeusly enhanced by electron beam (EB) irradiation. The cross-linking promoter, trimethylolpropane triacrylate (TMPTA), was also introduced into the blends to induce the cross-linking. By applying EB irradiation, the tensile modulus, hardness, swelling, cross-link density, and storage modulus increased with increase in the irradiation dose; an irradiation dose of 50 kGy was efficient to gain optimum tensile strength. The formation of irradiation-induced cross-links after EB irradiation is a major concern for the enhancement of mechanical, swelling resistance, and dynamic mechanical properties of the blends.
This article describes the structure changes of high-density polyethylene (HDPE) during stress and photo-oxidative aging experiments, and the relationship between different materials and cracking time. The three most representative grades of HDPE are 9070, TR480, and 2480NT. The average molecular weight, the comonomer type, and content of materials were measured by high-temperature gel permeation chromatography, 13C nuclear magnetic resonance (NMR) spectroscopy, and successive self-nucleation and annealing technique. Moreover, tensile testing was done to distinguish different toughness of materials. The samples were exposed to 5 MPa stress and ultraviolet irradiation in an aging oven, and observed at time intervals. The changes in structure were characterized by metallurgical microscopy, differential scanning calorimetry, attenuated total reflection-Fourier transform infrared spectroscopy, X-ray diffraction, and gel content measurements. With increasing time, the crystallinity increased, whereas melting point and oxygen induction times decreased. Meanwhile, the carbonyl index values and gel content reached about 10% until the samples were cracked. The results manifested that the resistance to cracking of the different HDPEs followed the order: 2480NT > TR480 > 9070. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40904.
Abstract Compounding is a unique requirement of the rubber, generally not
found in other material. The performance properties can be controlled by properly
selecting and adjusting various compounding ingredients. The stages of rubber
product manufacturing are broken down into three primary classes: selection of
compounding ingredients, mixing or compounding, and vulcanization techniques
or final product manufacturing process. The present chapter gives a brief introduction of the all classes with their importance. By proper selection of the variables in each class, the properties can be manipulated from virtually
incompressible with a bulk modulus some thousand times greater than shear
modulus, to large extent impermeable to gases and liquids and with excellent
recovering and abrasion resistance etc.
This paper is concerned with the technology of thermoplastic natural rubber/polyolefin blends that provide a wide variety of hard, flexible materials which can be prepared in conventional rubber mixing equipment and injection molded in overall cycle times of 13-40 seconds plus the dry cycle and mold stripping times. Injection molding cycle times are significantly shorter than the cycle times required by materials which need to be vulcanized. The physical properties of the blends suggest that they will be useful as stiff, flexible components in the car and footwear industries. They are sufficiently stiff in the working temperature range of minus 30 to plus 70 degree C to be considered for front and rear end components of cars. They have a desirably small temperature coefficient of stiffness in this range which makes them competitive with or superior to other materials such as polyurethanes or EPDM.
A study of dynamic mechanical thermal analysis of electron beam irradiated low-density polyethylene grafted with methyl methacrylate monomer has been performed. Three types of relaxations, namely, γ-, β- and α-, have been observed in the dynamic mechanical spectra of the samples. The effects of grafting and irradiation on these relaxations have been investigated.
Nylon-6 and acrylate rubber (ACM) were melt blended in a Brabender Plasticorder at 220°C and 40 rpm rotor speed. The reactive nature of the blend is reflected in the mixing torque behavior of the blends at different compositions. The solubility characteristics of the blends in formic acid solution gives an approximate idea of the amount of nylon-6 grafted onto ACM and vice-versa. A reaction mechanism is proposed based on the well known epoxy-amine and epoxy-acid reactions and is confirmed by infrared spectroscopic studies of the blends. The influence of interaction between the two polymers on the mechanical and the dynamic mechanical properties of the blends is analyzed in detail, and the results are interpreted on the basis of the formation of nylon-ACM graft copolymer at the interfaces. The dynamic mechanical thermal analysis (DMTA) reveals a two phase morphological structure, indicating incompatibility of the blend components. The grafting reaction results in dramatic increase in both the storage modulus and the Young's modulus of blends. The presence of grafted rubber chains is reflected in the secondary transition of the rubber loss peak at higher temperature. Also, a substantial improvement in the damping properties of the blends in the service temperature range (i.e., 25 to 175°C) is revealed from the DMTA results. The dynamic vulcanization of the ACM phase during melt mixing improves the elongation at break values of the blends.
Acrylamide was graft copolymerized onto LDPE, EVA and LDPE/EVA films using gamma radiation. The effects of different parameters such as monomer concentration, inhibitor concentration and radiation dose on the graft yield was studied. The grafted films obtained were characterized by using their water uptake, spectroscopic analysis and thermal analysis using differential scanning calorimetry. It was found that such grafted films can be used for copper ion recovery from their aqueuos solutions with an efficiency of up to 98%. It was also established that grafted films deteriorate very rapidly under the effect of UV radiation as the grafted part acts as photosensitizer.
The value of additives for increasing yields in radiation grafting reactions is discussed. The possible significance of the work in concurrent grafting during radiation curing is evaluated. Additives previously found to be effective in radiation grafting and reviewed here include acids, inorganic salts, organic inclusion compounds like urea, multifunctional acrylates and methacrylates. Synergistic effects in performance between the first three groups and the latter two have also been observed. Two new classes of compounds as additives in radiation grafting are reported and their reactivities compared with the earlier series. These new additives are oligomer acrylates and photoinitiators. In a mechanistic discussion related to these additives, a novel proposal involving partitioning phenomena is outlined to explain their modes of action.
The effect of electron beam irradiation at different radiation doses (2, 5, 10, 15, and 20 Mrad) on trimethylol propane trimethacrylol propane trimethacrylate (TMPTMA), ethylene vinyl acetate (EVA, 12% vinyl acetate content), and their blends (0.5, 1, 1.5, 2, 2.5, 3, and 5 parts/100 parts EVA) was investigated. An IR study showed some residual unsaturations retained in irradiated pure TMPTMA, while in blends all unsaturations were used up at a very early stage of irradiation. The concentration of the carbonyl group due to air oxidation increased in pure EVA and blends, but it reached a maximum at the 1.5-part TMPTMA level and 5-Mrad dose. some ether linkages were formed during irradiation in pure EVA and the blends, although in pure EVA the concentration of ether linkages reached a maximum at the 2-Mrad dose and then decreased and in the blends it increased with an increase in radiation dose. Gel content showed an increasing trend with an increase in radiation dose, but it increased marginally with TMPTMA level. A blend of EVA with 1 part TMPTMA produced more gel than pure EVA at the same irradiation dose. © 1996 John Wiley & Sons, Inc.
The crosslinking of moulded plastic parts extends the range of application of thermoplastic polymers by the improvement of their thermal and chemical stability. Radiation processing is unique for many of these products because the application of other crosslinking methods is not possible or has at least large drawbacks.Some technical aspects of the radiation treatment of moulded plastic parts on a production scale are discussed. Accelerators, supplying electron beams with energies above 2 MeV, are generally the preferred radiation source in this field. The temperature rise within the irradiated product has to be taken into account when higher doses must be applied.Examples of areas of application are given in which the improvement of the thermal stability and the resistance against stress corrosion of moulded plastic parts by radiation crosslinking are of importance. The reduction of the premeation rate through polymers resulting from crosslinking, is of interest for the gas tanks of passenger cars. The production of plastic parts with different properties in fractions of one single item by using shielding masks opens the designer new possibilities. In the case of elastomers a radiation treatment can supplement the heat vulcanization process and improve the uniformity of the product quality.
The effect of electron beam irradiation and EVA content upon the gel- forming processes in LOPE-EVA films has been studied. The yields of the gel- forming processes in the dose interval (0-250) kGy are different for each dose, but do not depend on the dose rate of the electron beam irradiation, while the different dose rates have different effect upon the gel formation in pure LDPE films. The EVA component reduces strongly the changes in the radiationally sensitive sublevels at irradiation and thus the decisive role of the dose rate is excluded. The gel content does not depend on the percentage of EVA in the LDPE-EVA mixtures either. The effectiveness of the gel-forming processes at irradition of the LDPE-EVA films with doses above 16 Mrad is considerably reduced, because the radiation-induced chemical crosslinking is realized predominantly between already crosslinked macromolecular chains.
The equation for the sol fraction (s) of a cross-linked polymer network becomes readily tractable when applied to special cases of the generalized distribution function n(u) = C(u/u1)lambda -1 exp (-lambda u/u1). For values of lambda = ∞ , 1 and 0 respectively, this function yields the uniform distribution, the exponential distribution and a hypothetical pseudo-random distribution. Assuming that cross-linking and fracture occur at random and in proportion to the radiation dose, simple expressions are derived relating sol fraction to radiation dose (r) for each of the three distributions. The most useful of these is the relation involving the fracture density per unit dose (p0) and the density of cross-linked units per unit dose (q0). s + surd s = p0/q0 + 1/q0u1r. This holds strictly for exponential distributions, whether or not main-chain fracture occurs simultaneously with cross-linking, and also holds at high doses for the other distributions considered, providing that cross-linking is accompanied by fracture. This treatment is applied to experimental results on low-density and high-density polyethylenes, polyvinyl acetates, polyvinyl chloride, polypropylene and polyalkyl acrylates. The relevant radiation parameters p0, q0 and the corresponding G values are deduced. It is found, in the case of polyethylene, that q0 is, within experimental error, independent of the molecular weight, degree of branching or crystallinity, but is affected by the presence of air. Similar values of q0 are also observed for polyvinyl acetate and polyvinyl chloride.
The heat shrinkability of electron-beam-irradiated thermoplastic elastomeric films from blends of ethylene–vinylacetate copolymer (EVA) and low-density polyethylene (LDPE) has been investigated in this paper. The effects of temperature, time and extent of stretching and shrinkage temperature and time have been reported. Based on the above data, the optimized conditions in terms of high heat shrinkage and low amnesia rating have been evaluated. Influence of radiation doses (0–500kGy), multifunctional sensitizer levels (ditrimethylol propane tetraacrylate, DTMPTA), and blend proportions on heat shrinkability has been explained with the help of gel fraction and X-ray data. With the increase in radiation dose, gel fraction increases, which in turn gives rise to low values of heat shrinkage and amnesia rating. At a constant radiation dose and blend ratio, percent heat shrinkage is found to decrease with increase in DTMPTA level. Gel content increases with the increase in EVA content of the blend at a constant radiation dose and monomer level, giving rise to decrease in heat shrinkability. Heat shrinkage increases with the increase in percent crystallinity, although the amnesia rating follows the reverse trend.
Natural rubber–polyolefin (70/30) blends have been studied by incorporation of modified rubber and plastic phases with a view to make the heterogeneous phases compatible. The modified rubbers used were epoxidized natural rubber (ENR) and sulfonated ethylene–propylene diene rubber (S-EPDM) at a level of 20 parts. Other rubbers such as chlorinated polyethylene (CPE) and ethylene propylene diene rubbers (EPDM) were also used at a level of 20 parts in the natural rubber–polyethylene (NR/PE) systems. The plastic phase was chemically modified with maleic anhydride (MA) in presence of benzoyl peroxide (BPO) and used at a concentration of 10% of PE, i.e., PEm. The tensile properties such as the modulus, elongation at break, tensile strength, and hysteresis were studied. NR/ENR/PEm/PE shows the greatest improvement in tensile strength (45% over control NR/PE). NR/S-EPDM/PEm/PE also shows similar improvement, although the hysteresis loss decreases. The change in these properties could be related to the adhesive strength. This was found to be improved by the incorporation of modified rubber and modified plastic phases. The best adhesion values have been obtained with NR/ENR/PEm/PE and NR/S-EPDM/PEm/PE. Thus, a correlation between tensile and adhesive strength was obtained for all the systems. The increase in adhesive strength is due to chemical reactions between the various phases. Probable chemical reactions have been suggested. Morphological observations show that the phases are interpenetrating, and this is consistent with the increased tensile strength. The natural rubber–polypropylene (NR/PP) systems do not offer good strength properties with the modified PP and modified rubbers. The adhesive strength also decreases with the incorporation of the modified system. The hysteresis properties show some improvement.
Electron beam-initiated crosslinking of films prepared from a blend of low-density polyethylene (LDPE) and ethylene–vinyl acetate (EVA) containing 45% vinyl acetate, with ditrimethylol propane tetraacrylate (DTMPTA), was carried out over a range of radiation doses (20–500 kGy), concentration of DTMPTA (1–5 parts by weight), and blend compositions. The gel fraction of the films increases with increase in the irradiation dose, DTMPTA level, and EVA content of the blends. The mechanical and dynamic mechanical properties of the films are also changed with the above variables. Reprocessibility studies revealed that the blends irradiated at 50 kGy and below are thermoplastic elastomers with a low permanent set. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1877–1889, 2001
Electron-beam (EB)-initiated grafting of triallyl cyanurate (TAC) onto polyethylene (PE) has been carried out over a range of radiation dose (2–20 Mrad) and concentrations of TAC (0.5–3 parts by weight). The grafting level, as determined from IR spectroscopy, is maximum at a 10 Mrad radiation does using 1 part TAC. With increasing TAC level at a 15 Mrad dose, the grafting level is higher only after 1.5 parts TAC. The gel content increases with radiation dose in the initial stages. X-ray studies indicate two peaks at 10.6–10.8° and 11.7–11.9° and the corresponding interplaner distances of 4.15 and 3.80 Å. With increase in radiation dose or TAC level, the crystallinity decreases in the initial stage and then increases. It shows a decreasing trend again at higher radiation dose. The interplanar distance or the interchain distance of the modified polymer does not change. However, the crystallite size increases initially and then decreases. The tensile properties are relatively insensitive to the variation of radiation dose because of the interplay of various factors. The dielectric loss, tan δ, shows a maximum at a 10 Mrad dose and minimum at 5 and 15 Mrad due to changes of polarity and the carrier mobility. © 1994 John Wiley & Sons, Inc.
Dynamic mechanical properties determined with a torsion pendulum were used to ascertain the glass transition temperature Tg of poly-ε-caprolactone. By measurements on compatible blends of poly-ε-caprolactone and poly(vinyl chloride), the Tg of amorphous poly-ε-caprolactone was shown to be 202°K at about 1 cps. This is 16°K lower than the Tg of annealed, crystalline polymer. The blend transition data were well fitted by both the Fox and the Gordon-Taylor expressions. The Fox expression was also used to describe the decrease from 233°K of the secondary low-temperature relaxation due to poly(vinyl chloride) by assuming the low temperature relaxation of poly-ε-caprolactone, 138°K, was responsible for the decrease in the blends. The 138°K relaxation due to poly-ε-caprolactone was decreased when more than 50% poly(vinyl chloride) was present.
An investigation has been carried out into the effect of irradiation dose and the amount of the unsaturated monomer trimethylolpropane trimethacrylate (TMPTMA) on the irradiation of a di-iso-octyl phthalate (DIOP) plasticized PVC compound. The type of network structure produced and the extent of deterioration of the PVC after crosslinking have been studied. Within the dose range studied, the degradation caused by the electron beam was found to be minimal, but the residual unsaturation in the crosslinked PVC was significant, implying inefficient use of crosslinking agent. Gel yield increased with increased irradiation dose and TMPTMA content, but crosslink density decreased at higher irradiation levels, suggesting the formation of a looser network. The phthalate plasticizer was not involved in gel formation.
The influence of electron beam irradiation on the mechanical and dynamic mechanical properties, gel fraction and crosslink density of terpolymeric fluorocarbon rubber has been investigated in this paper. An attempt has been made to correlate the structure of the irradiated rubber with the properties. With increase in radiation dose, an increase in degree of crosslinking results which leads to increase in modulus and Tg with a corresponding decrease in elongation at break, set and tan δ. The effect of multifunctional monomer is realized only at relatively higher level of trimethylolpropane triacrylate (TMPTA), where improvement in strength and failure properties is observed. The dynamic storage modulus at 50°C is higher and loss tangent becomes lower. Among the various polyfunctional monomers tripropyleneglycol diacrylate (TPGDA), trimethylolpropane triacrylate (TMPTA) and tetramethylolmethane tetracrylate (TMMT), the mechanical properties and the degree of crosslinking are lowest for systems based on TPGDA. MgO used in the formulation leads to the improvement in mechanical properties. Increase in the crosslink density is in line with reduced loss tangent and increased storage modulus for the MgO filled rubber vulcanizate.
Low density poly(ethylene/ethylene-vinylacetate) blends were exposed to γ radiation at doses between 100 and 160 kGy, at room temperature, to study the effects of a trifunctional acrylic monomer, TMPTMA, and two antioxidants on their properties. The effects of irradiation on mechanical behavior, crosslinking/dose ratio, thermal aging and crystallinity were studied. Gel fractions up to 0.7 and 30% increments in crosslinking/dose ratio were obtained. Noticeable changes in mechanical properties; tensile strength, elongation at break. Young modulus and hardness were also observed. The effects on crystallinity of both irradiation and a post-irradiation thermal treatment were analyzed by X-ray diffraction. Crystallinity was not significantly affected by irradiation but it decreased after the aging treatment. The latter effect is associated with crosslinking and probably with active species (e.g. free radicals) remaining in the crystalline phase for a long time after irradiation. Possible chemical reactions and alternative irradiation methods are also discussed.
Electron beam initiated grafting of trimethylol propane triacrylate (TMPTA) onto ethylene propylene diene monomer (EPDM) has been carried out over a wide range of irradiation doses (0–200 kGy) using a fixed concentration (10%) of TMPTA. The samples have been both surface and bulk modified. Infrared (IR) studies indicate increased peak absorbances at 1730, 1260, 1120 and 1019 cm−1 upto 50 kGy and hence increased CO and C–O–C concentrations. The results are further supported by X-ray photoelectron spectroscopy (XPS) studies. The surface energy of EPDM increases from 46.5 to 60.7 mJ/m2 on irradiation of the surface modified samples to 50 kGy dose, due to increased contribution of γSAB and γS(−). The results have been explained with the help of IR and XPS data. The values of tensile strength of the surface modified samples have not changed very significantly, while the moduli values have increased at the cost of the elongation at break. DMTA studies have shown changes in Tg and tan δmax on modification of the surface. The surface morphology of the modified and irradiated samples reveals acrylate flow marks at high magnification.
- Datta