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Cationic photocued epoxy nanocomposites filled with different carbon fillers
... It is possible to observe that the filled materials showed higher glass transition temperature (T g ) values than the epoxy, which is evidenced by the shift of the maximum of the Tan δ peaks. It is well known that the addition of rigid fillers in epoxy matrices can hinder the polymer chain movements, leading to a damping effect and a shift of T g values to higher temperatures [35]. In this study a shift of T g (up of 12°C) and a damping decrement (evaluated as Tan δ max ) were observed in the hybrid GO/h-BN composite with 0.5 wt% when compared to the pure epoxy [13,36]. ...
... Composites Science and Technology xxx (2018) xxx-xxx increase in T g , storage modulus, and a damping effect of rigid nanofiller in polymer systems are generally attributed to a strong filler-matrix interface, since they restrict the mobility of the epoxy chains [35][36][37]. An up shift of 20°C in T g was observed by Martin-Gallego et al. in epoxy composites filled with functionalized graphene-silicone with 1.0 wt% [35]. ...
... Composites Science and Technology xxx (2018) xxx-xxx increase in T g , storage modulus, and a damping effect of rigid nanofiller in polymer systems are generally attributed to a strong filler-matrix interface, since they restrict the mobility of the epoxy chains [35][36][37]. An up shift of 20°C in T g was observed by Martin-Gallego et al. in epoxy composites filled with functionalized graphene-silicone with 1.0 wt% [35]. Yu et al. observed increases up to 26°C in T g for boron nitride functionalized with octadecylamine (ODA) composite with 5.0 wt% content in epoxy [38]. ...
... The presence of dispersed carbon nanotubes (CNT) in epoxy coatings in amount of below 0.5 wt.% significantly improves many of their properties, i.e. electrical conductivity [1][2][3][4][5][6][7], electric heating behavior [4], corrosion resistance [6][7][8][9][10][11][12][13][14][15][16], barrier [10], galvanic protection [10], glass transition temperature [1][2][3], thermal stability [6,[16][17][18], hardness [2,19], storage modulus [1][2][3], Young modulus [17], tensile strength [20], elongation at break [20], adhesion [7,[12][13][14][15]17], flexibility [15], hydrophobicity [14] as well as resistances to environmental degradation [5], abrasion [12,18], impact [8,16], bending [8], cupping [8], scratch [1] and wear [17,19]. Unluckily, there are some substantial problems with CNT-modified epoxy coatings which makes them unattractive for implementation. ...
... The presence of dispersed carbon nanotubes (CNT) in epoxy coatings in amount of below 0.5 wt.% significantly improves many of their properties, i.e. electrical conductivity [1][2][3][4][5][6][7], electric heating behavior [4], corrosion resistance [6][7][8][9][10][11][12][13][14][15][16], barrier [10], galvanic protection [10], glass transition temperature [1][2][3], thermal stability [6,[16][17][18], hardness [2,19], storage modulus [1][2][3], Young modulus [17], tensile strength [20], elongation at break [20], adhesion [7,[12][13][14][15]17], flexibility [15], hydrophobicity [14] as well as resistances to environmental degradation [5], abrasion [12,18], impact [8,16], bending [8], cupping [8], scratch [1] and wear [17,19]. Unluckily, there are some substantial problems with CNT-modified epoxy coatings which makes them unattractive for implementation. ...
... The presence of dispersed carbon nanotubes (CNT) in epoxy coatings in amount of below 0.5 wt.% significantly improves many of their properties, i.e. electrical conductivity [1][2][3][4][5][6][7], electric heating behavior [4], corrosion resistance [6][7][8][9][10][11][12][13][14][15][16], barrier [10], galvanic protection [10], glass transition temperature [1][2][3], thermal stability [6,[16][17][18], hardness [2,19], storage modulus [1][2][3], Young modulus [17], tensile strength [20], elongation at break [20], adhesion [7,[12][13][14][15]17], flexibility [15], hydrophobicity [14] as well as resistances to environmental degradation [5], abrasion [12,18], impact [8,16], bending [8], cupping [8], scratch [1] and wear [17,19]. Unluckily, there are some substantial problems with CNT-modified epoxy coatings which makes them unattractive for implementation. ...
Epoxy thin coatings, containing 0.025–0.5 wt.% of carbon nanotubes (CNT), exhibited outstanding combination of transparent and surface conductive properties, showing transparency up to 83% and electrical surface resistivity decreased by up to 10 orders of magnitude, accompanied by the highest chemical resistance to methyl-ethyl ketone, improved thermal stability up to 20 °C, perfect adhesion and considerable hardness. Such significant improvement of numerous properties of coatings was possible thanks to the use of neutralized o-tolylbiguanide/epoxy resin dispersing medium characterized by low viscosity and strong tendency to create π-π electron interactions with CNT. This enabled non-covalent functionalization and dispergation of CNT in varnish via common, industrially applicable one-step process, driven by mechanical mixing.
... Nanocomposite polymer films and coatings with recently discovered carbon nanoparticles (CN), i.e. carbon nanotubes (CNT) or graphene (GNP) exhibit many improved properties, such as electrical conductivity [1][2][3][4][5][6][7][8][9][10][11], anticorrosion/ barrier features [5,[12][13][14][15][16][17][18][19][20][21][22][23], thermal stability [6,10,11,14,19,21,22,[24][25][26][27] , hydrophobicity [11,18,28], adhesion to different substrates [5,13,16,18,20,23,25] as well as mechanical features (i.e. hardness [2,6,10,11,29], tensile strength [4,23,24,30,31], impact strength [14,15,22]). ...
... Nanocomposite polymer films and coatings with recently discovered carbon nanoparticles (CN), i.e. carbon nanotubes (CNT) or graphene (GNP) exhibit many improved properties, such as electrical conductivity [1][2][3][4][5][6][7][8][9][10][11], anticorrosion/ barrier features [5,[12][13][14][15][16][17][18][19][20][21][22][23], thermal stability [6,10,11,14,19,21,22,[24][25][26][27] , hydrophobicity [11,18,28], adhesion to different substrates [5,13,16,18,20,23,25] as well as mechanical features (i.e. hardness [2,6,10,11,29], tensile strength [4,23,24,30,31], impact strength [14,15,22]). In some cases, higher cupping [15], scratch [7,23,27] and abrasion [13,26] resistance of CN-filled materials are observed as well. ...
... The most common way to solve that problem is a surface functionalization of the nanoparticles [32]. Thus, CN for coating applications are modified by covalent [2,3,9,12,14,16,[20][21][22]26,27,[29][30][31] or non-covalent methods using dispersing agents [1,6,9,11,17,19,24]. Unluckily, covalent methods seriously increase CN price and often negatively influence on features (mainly electrical conductivity [2]) of CN/polymer nanocomposites. ...
Solventless epoxy varnishes and coatings were prepared using carbon nanotubes (CNT) and/or graphene (GNP) dispersions in a Bisphenol F-type epoxy resin, synthetic hardeners [tetraethylenepentamine, poly(oxyethylene)diamine, isophoronediamine, m-xylylenediamine] or bio-based amine hardener (Cardanol-based phenalkamine, abbreviationabbreviation: PAA). Room temperature cured coatings, containing 0.35 wt.% of CNT predispersed in PAA, showed outstanding combination of optical (i.e. high gloss and transparency, low haze in humid conditions) and electrostatic dissipative properties (surface resistivity ca. 5.5 × 10⁷ Ω) in relation to the samples containing carbon nanofiller(s) dispersion in the epoxy resin or a synthetic amine. PAA-based coatings with the carbon nanofillers exhibited increased cupping resistance (+20% for samples with CNT) as well as high hardness and excellent adhesion to a glass substrate. The carbon nanofillers addition influenced on curing process and glass transition temperature (monitored using differential scanning calorimetry technique) of the epoxy varnishes and coatings as well.
... These properties identify graphene as an optimal reinforcement filler for the production of composites with a nano-sized component. As reported in previous research [8,9,10,11,12,13], the modulus and glass transition temperature of composites can be effectively increased with the use of graphene as an additive to epoxy resin. Graphene also demonstrates high electrical and thermal conductivity, such as that of graphite and carbon nanotubes [14,15,16]. ...
... After the introduction of θ cut-off , the orientation average of the graphene distribution is accounted for by Eq. (11). θ cut-off is the upper limit in the integration in Eq. (12). The relationship between the CTE of the graphene/epoxy composite and the distribution cut-off angle θ cut-off was calculated for three fixed aspect ratios: 0.1, 0.01, and 0.001. ...
... The parameters used in the simulation are listed in Table 1. According to the experimental results, the aspect ratio of the simulation was set to 0.02 for GNP/ PEId [20] and 0.001 for graphene/epoxy [12]. The orientation angle distribution can be measured by SEM following further image analysis [20]. ...
In this paper, theoretical calculations were conducted to determine the coefficient of thermal expansion (CTE) based on the effective medium approach using Green’s function method. The influences of microstructural features were investigated, including volume fraction, aspect ratio, and the orientation of graphene fillers. Calculated results demonstrated strong anisotropy of CTE when all graphene sheets in the composite were aligned in the in-plane direction due to the large difference between the elastic moduli of the graphene and epoxy. The in-plane CTE in the graphene/epoxy composite can be effectively reduced with small additions of graphene additive. Orientation dispersion among the graphene fillers significantly decreases the anisotropy of CTE. Accounting for the influences of all microstructural features, simulation results closely align with current experimental results. This work will provide a general guideline and a solid foundation for the optimal design and preparation of graphene/polymer composites.
... Both concentrations of TRGO (1 wt.% and 1.5 wt.%) and 0.5 wt.% CNT are above the percolation threshold for the two sets of foam densities, where the 0.5 wt.% MWCNT sample shows the highest value of electrical conductivity, close to 10 −5 S/m. Previous articles by the authors have also observed differences in the percolation threshold and electrical conductivities of CNT and TRGO filled solid epoxy resins, which were ascribed to the geometry of the fillers [26,44], and have later been corroborated by other authors [45]. ...
... Both concentrations of TRGO (1 wt.% and 1.5 wt.%) and 0.5 wt.% CNT are above the percolation threshold for the two sets of foam densities, where the 0.5 wt.% MWCNT sample shows the highest value of electrical conductivity, close to 10 -5 S/m. Previous articles by the authors have also observed differences in the percolation threshold and electrical conductivities of CNT and TRGO filled solid epoxy resins, which were ascribed to the geometry of the fillers [26,44], and have later been corroborated by other authors [45]. ...
Owing to their high strength and stiffness, thermal and environmental stability, lower shrinkage, and water resistance, epoxy resins have been the preferred matrix for the development of syntactic foams using hollow glass microspheres. Although these foams are exploited in multiple applications, one of their issues is the possibility of breakage of the glass hollow microspheres during processing. Here, we present a straightforward and single-step foaming protocol using expandable polymeric microspheres based on the well-established compression molding process. We demonstrate the viability of the protocol producing two sets of nanocomposite foams filled with carbon-based nanoparticles with improved transport properties.
... where is the direct current conductivity, A is a pre-exponential factor and s is an experimental parameter with values between 0 and 1 [32]. For insulating materials s = 1. ...
... where σ DC is the direct current conductivity, A is a pre-exponential factor and s is an experimental parameter with values between 0 and 1 [32]. For insulating materials s = 1. ...
Multifunctional elastomer nanocomposites have been applied in several high-tech fields. The design of materials with tailored properties capable of tuning their performance is a topical challenge. Here, we demonstrate that it is possible to modulate the mechanical and transport properties of silicone rubber nanocomposites by controlling the structure, chemical composition and morphology of the graphene material. Intrinsic graphene properties, such as remaining oxygen groups, specific surface area, and aspect ratio, among others, have a profound effect on the final properties of the nanocomposite. Thus, the thermal conductivity benefits from larger filler size and high aromatic restoration. Whereas mechanical properties and electrical conductivity require a proper balance between filler/polymer matrix interaction and a partial aromatic restoration.
... The effects of nanofiller geometry [19][20][21][22] and nanofiller hybrid mixtures [13,[23][24][25][26][27][28][29] on the characteristics nanocomposites have been recently investigated. For instance, Martin-Gallego et al [19] reported that CNT/ epoxy nanocomposite has lower electrical percolation threshold than expanded a graphite (EG)/epoxy composite because the dispersion of the 1D CNT is easier than that of the 2D EG. ...
... The effects of nanofiller geometry [19][20][21][22] and nanofiller hybrid mixtures [13,[23][24][25][26][27][28][29] on the characteristics nanocomposites have been recently investigated. For instance, Martin-Gallego et al [19] reported that CNT/ epoxy nanocomposite has lower electrical percolation threshold than expanded a graphite (EG)/epoxy composite because the dispersion of the 1D CNT is easier than that of the 2D EG. Using molecular dynamics simulations, Liu et al [23] demonstrated a synergetic effect of a CNT:graphene mixture on improving the interfacial adhesion at the nanofiller/polymer interface. ...
Nanocomposites are advanced engineering materials with multifunctional characteristics and numerous applications in the packaging, automotive, construction, and energy sectors. In this work, the effects of nanofiller geometry on the processing behavior, interfacial interaction, and electrical percolation behaviors of melt-mixed polystyrene (PS) nanocomposites were investigated. This paper also reports on the synergistic influence of incorporating multi-nanofiller mixture on the electrical resistivity of polymer nanocomposites. Two nanofillers of different geometries and electrical conductivities, namely carbon nanotubes (CNTs) and high-structure carbon black (CB), were used to prepare the nanocomposites. CNTs have a rod-like (1D) shape, whereas CB is characterized by an irregular-branched shape. Because CNTs have higher aspect ratio and electrical conductivity than CB, the CNT-based composites exhibited lower electrical resistivity and electrical percolation threshold than the CB-based composites. The analysis of the percolation behaviors showed that the network formation in the CNT/PS and CB/PS composites can be attributed to the kinetic percolation rather than the statistical percolation. Most interestingly, the CNT:CB/PS composites with a CNT:CB mass ratio of 75:25 showed higher electrical conductivity than the CNT-based and the CB-based composites, revealing a synergetic effect on the electrical properties at this nanofiller ratio.
... It is possible to observe that the filled materials showed higher glass transition temperature (T g ) values than the epoxy, which is evidenced by the shift of the maximum of the Tan d peaks. It is well known that the addition of rigid fillers in epoxy matrices can hinder the polymer chain movements, leading to a damping effect and a shift of T g values to higher temperatures [35]. In this study a shift of T g (up of 12 C) and a damping decrement (evaluated as Tan d max ) were observed in the hybrid GO/h-BN composite with 0.5 wt% when compared to the pure epoxy [13,36]. ...
... The increase in T g , storage modulus, and a damping effect of rigid nanofiller in polymer systems are generally attributed to a strong filler-matrix interface, since they restrict the mobility of the epoxy chains [35e37]. An up shift of 20 C in T g was observed by Martin-Gallego et al. in epoxy composites filled with functionalized graphene-silicone with 1.0 wt% [35]. Yu et al. observed increases up to 26 C in T g for boron nitride functionalized with octadecylamine (ODA) composite with 5.0 wt% content in epoxy [38]. ...
... GNPs was found to follow the universal dynamic response (UDR) behavior. Martin-Gallego et al. 18 compared the electrical percolation threshold (EPT) of CNT-epoxy with that of expanded graphite (EG)epoxy. The CNT-based nanocomposite showed lower EPT because of the rod-like, 1D geometry of CNTs, which is more effective than the sheet-like, 2D geometry of graphene for building conductive networks. ...
... This behavior has been reported for nanocomposites based on CNTs, 28,29,40 carbon black, 30 copper nanowires, 41 and EG. 18,19 It is apparent that, with increase in the GNP concentration (i.e., increase in conductive networks), r¢ increased and the frequency-independent region broadened to higher frequencies. In the frequency-dependent region, the increase in conductivity with frequency can be attributed to removal of any charge buildup due to space charge. ...
Graphene nanoplatelet (GNP)–polystyrene nanocomposites filled with up to 20 wt.% GNPs were prepared by melt mixing. The microstructure, direct-current (dc) electrical percolation behavior, and dielectric characteristics were investigated as functions of frequency. In addition, the effects of dc bias on the complex impedance and charge transport mechanisms were explored. The dc electrical percolation curve showed a gradually transition from the insulating to conducting state. At 15 wt.% GNP loading and frequency greater than 104 Hz, the nanocomposite exhibited dielectric constant and loss factor of 180 and 0.11, respectively, revealing remarkable storage capabilities at high frequencies. For nanocomposites filled with 12 wt.% to 20 wt.% GNPs, the alternating-current conductivity was found to follow the universal dynamic response behavior, implying electron conduction due to tunneling in addition to direct contact between GNPs.
... Graphene is a possible reinforcement in nanocomposites due to its huge specific surface area and 2D layer structure, in addition to its exceptional mechanical properties. Graphene sheets and Ep resin have been mixed in a number of investigations to form nanocomposites, and the results indicate that the modulus and glass transition temperature of these materials can be greatly increased [18][19][20][21][22][23][24]. Graphene is the strongest material ever measured, according to experiments by Lee and colleagues [22]. ...
... Numerous fillers have been used to fabricate polymer composites with low CTE. 72,73 Various factors, such as volume fraction, aspect ratio, and orientation of fillers, have been involved in effecting the CTE of composites. 74 The CTE of the prepared epoxy composites in the presence of Al 2 O 3 @BNNT and Al 2 O 3 @ ODA-BNNT was compared with that of neat epoxy polymer (Figure 4e). ...
Over the past few years, the ability to efficiently increase boron nitride nanotube (BNNT) production has opened up ample research possibilities. BNNT has garnered significant attention for diversifying its industrial applications. However, the problem of poor processability resulting from agglomeration and uneven distribution has emerged as a major challenge to integrating BNNT into the polymer matrix for composite material formation. Utilizing noncovalently attached molecules with various reactive sites can be a logical method to enhance the compatibility of BNNT with different polymers. The present study explored a simple approach to protruding BNNT onto the surface of Al2O3 through tannic acid (TA)-assisted generation of alkyl chains (octadecylamine, ODA) to fabricate Al2O3@ODA-BNNT. The subsequent compounding of Al2O3@ODA-BNNT with epoxy polymer generates interconnected thermal conduction pathways, thereby improving the thermal conduction and mechanical performance of the composites. The current research approach allows for the even distribution of BNNT throughout the polymer matrix, as demonstrated by optical characterization, mechanical performance analysis, and isotropic thermal conductivity analysis. The fabricated epoxy composite by incorporating a 2 wt % (BNNT = 1.3 wt % and ODA = 0.7 wt %) ODA-BNNT exhibited 5.117 W/mK thermal conductivity and 7.43 MPa mechanical stress. Thermal conductivity improved by 2528, 76.56, and 54.7%, while mechanical stress enhanced by 270, 221, and 34% compared to neat polymers without BNNT and virgin BNNT epoxy composites, respectively.
... Then, changing the Young's modulus near the working temperature makes the SMP may achieve the ideal performance under service conditions. According to the reports of Shiu and Tsai 60 and Martin-Gallego et al. 61,62 introducing hydrophilic inorganic oxides into the polymer interior could be an effective method for increasing the glass transition temperature of SMP. Meanwhile, according to the study reported by Ji et al., 63 it can be found that the addition of inorganic fillers is one of the available ways to improve the Young's modulus of polymer composites. ...
The quantitative characterization of the tensile strength of shape memory polymers (SMPs) at different temperatures has always been an important research topic. In this study, the critical failure energy density of SMPs including the strain energy density, potential energy and kinetic energy of atomic motion per unit volume is first introduced. Then, based on the equivalent contribution of these energies on material failure, a temperature dependent tensile strength (TDTS) model considering the corresponding physical mechanism for SMPs is established. The model provides the quantitative relationship among temperature, Young's modulus, hardening index and the tensile strength of SMPs. Meanwhile, the predicted results of the proposed model are compared with the available TDTS of SMPs, and the agreement between theory and experiment is satisfactory. In addition, the influencing factors of tensile strength and their variation with temperature are analyzed. This work contributes the novel insight for the theoretical predictions on the TDTS of SMPs, which is helpful for the high temperature strength evaluation and property optimization.
... Besides, the polymerization reaction may be affected by the nanomaterial [44,45] if they act as chain transfer agent, thereby inhibiting polymer chain growth [39] , or as free radical scavengers that reduce the extent of polymerization reaction [46,47] .These effects make studying the influence of nanomaterials especially important, specifically their effect on the polymerization reaction of photocurable resins and in the context of efficacious 3D printing, as these modifications can affect printability and the practicality of a particular 3D printing technique. These effect depends on many factors, for example, type and specific surface area of the nanomaterial -the latter factor affects the extents of shielding, which can affect the degree of polymerization [48] . ...
Additive manufacturing is gaining importance thanks to its multiple advantages. Stereolithography (SLA) shows the highest accuracy and the lowest anisotropy, which has facilitated the emergence of new applications as dentistry or tissue engineering. However, the availability of commercial photopolymers is still limited, and there is an increasing interest in developing resins with properties adapted for these new applications. The addition of graphenebased nanomaterials (GBN) may provide interesting advantages, such as improved mechanical properties and bioactivity. However, there is a lack of knowledge regarding the effect of GBNs on the polymerization reaction. A photopolymerizable acrylic resin has been used, and the effect of the addition of 0.1wt% of graphene (G); graphene oxide (GO) and graphite nanoplatelets (GoxNP) on printability and polymerization have been investigated. It was observed that the effect depended on GBN type, functionalization and structure (e.g., number of layers, size, and morphology) due to differences in the extent of dispersion and light absorbance. The obtained results showed that GO and GoxNP did not significantly affect the printability and quality of the final structure, whilst the application of G exhibited a negative effect in terms of printability due to a reduction in the polymerization degree. GO and GoxNP-loaded resins showed a great potential to be used for manufacturing structures by SLA.
... The type of filling is crucial for the properties and possible application of the final product, therefore different types of nano additive have been tested, inter alia: natural [30] and polymeric fibres, [31] silica [32][33][34][35], aluminium oxides [36] and others [37][38][39][40]. Moreover, carbon nanotubes, which are often used in combination with epoxy resins [41,42] reacting according to the cation mechanism, are extremely interesting in terms of nanocomposites [43][44][45]. The second type of composites are fibre-reinforced composites, which can be manufactured in many ways, including: infusion process [46], compression and injection molding [47] or resin transfer molding [48]. ...
New meta- and para-cyanoderivatives of 1,4-di(styryl)benzene and 1,3-di(styryl)benzene were synthesized and investigated for their use as photosensitizers of iodonium salt for various photopolymerization processes. Detail spectroscopic characteristic of this compound were performed, and the mechanism of initiation in binary photoinitiating system together with iodine salt was discussed and confirmed by experiments. Using real-time FTIR, the usefulness of the proposed meta- and para-cyanoderivatives of 1,4-di(styryl)benzene and 1,3-di(styryl)benzene as highly efficient photosensitizers for various photopolymerization processes was tested, including: free-radical photopolymerization of acrylate monomer or cationic photopolymerization of epoxy and glycidyl monomers. In addition, the formation of interpenetrating polymer networks with the use of proposed two-component initiating systems was performed. Encouraged by excellent polymerization results with the use of the developed initiating systems, additional application tests were carried out, including: 3D printing using vat polymerization, visible based direct ink writing, preparation of various fiber-reinforced composite or formation of multiwalled carbon nanotubes composites (MWCNTs nanocomposites), for which the manufacturing process has been analyzed in detail using real-time FTIR method.
... The electronic conductivity is expected to be the most important contribution to electrical J o u r n a l P r e -p r o o f conductivity, as there is no evidence of an ionic contribution at low frequencies. In addition, it is observed that the dielectric permittivity decreases as the electric field frequency is increased, which has been associated to the interfacial polarization of graphene flakes [69,70]. In order to evaluate the performance of the PMMI-g-GO as potential electrode material for energy storage applications, a symmetric half-cell with lithium metal and PMMI-g-GO was assembled. ...
This work reports the synthesis of poly (monomethyl itaconate) grafted multi-layer graphene oxide (PMMI-g-GO) by atom transfer radical polymerization using activators regenerated by electron transfer (ARGET-ATRP). PMMI-g-GO presents outstanding properties, such as a high electrical conductivity (5.04 Sm-1), low number of stacked graphene layers (6) and IG/I2D ratio of 2.05 estimated from Raman spectrum, which indicates the high quality of PMMI-g-GO as a graphenic material. In addition, polymer brushes based on PMMI represent a new green alternative for the development of polymer composite materials, since the monomer used for their production is obtained from a renewable source. Interestingly, the PMMI-g-GO nanomaterial is also capable of storing Li+ ions without the need of using electron conductive additives that are usually employed in the electrode´s composition of conventional lithium ion batteries.
... 46,47 The compositions with added carbon nanotubes or graphite, based mainly on epoxy resins are cured by the cationic polymerization mechanism. 48,49 Usually, small quantities of CNTs, generally between 0.1% and 5.0% (w/w), are added to the polymeric matrix to improve not only the mechanical but also the thermal properties. For these reasons, obtaining composite materials of this type is extremely attractive. ...
A series of 2-(diethylamino)-4-(1-ethylpropyl)-6-phenyl-benzene-1,3-dicarbonitrile derivatives were investigated in terms of photosensitisation in various photopolymerization processes in UV-A and vis light conditions. A full spectroscopic analysis of the tested compounds was performed. In addition to excellent spectroscopic properties, these compounds enable highly efficient photopolymerization processes, including free-radical, cationic and hybrid photopolymerization. As proven by a real-time FTIR study, these photosensitisers allow the formation of both thin and thick layers from different monomers. Finally, the investigated 2-(diethylamino)-4-(1-ethylpropyl)-6-phenyl-benzene-1,3-dicarbonitrile derivatives were used to obtain multiwalled carbon nanotubes (MWCNTs) composites for which the degree of conversion was determined using real-time FT-IR and Photo-Differential Scanning Calorimetry (Photo-DSC). Selected derivatives were applied as photosensitisers in two-component photoinitiating systems, operating according to the mechanism of photo-oxidation and photo-reduction, for the preparation of photo-cured MWCNTs composites. The importance of the quantity of multiwalled carbon nanotubes (MWCNTs) added to the polymeric matrix on the curing degree is also discussed in this study. The structures of the MWCNTs composites were analysed using an optical and fluorescence microscope. Moreover, this study also examines the applicability of new photoinitiator systems for printing nanocomposites by vat photopolymerization, which has gained increasing attention in recent years. Therefore, photocurable nanocomposite resin based on methacrylates was used for 3D printing in room temperature and atmospheric conditions, under a visible LED with emission at 405 nm, in order to obtain fluorescent photocurable patterns.
... There are widespread researches in making and application of polymer Nano composites aiming improvement of polymer features and increasing their application capability in different areas [4]. Along with this, carbon based Nano particles like carbon Nanotubes [5][6][7][8][9] and Graphene [10][11][12][13][14][15][16] have attained special position in making polymer Nano composites. It should be noted that these Nano particles have different features like mechanical reinforcement, electrical conductance and heat stability in comparison with each other [16][17][18]. ...
Graphene is the newest member of the multidimensional graphite carbon family. Graphene is a two-dimensional atomic crystal formed by the arrangement of carbon atoms in the hexagonal network. It is the most rigid and thinnest material ever discovered and has a wide range of uses regarding its unique characteristics. It is expected that this material will create a revolution in the electronics industry. Graphene is a very powerful superconductor as the movability of charged particles is high on it, and additionally, because of the high surface energy and ? electrons being free, graphene can be used in manufacturing many electronics devices. In this paper, the applications of graphene nanoparticles reinforced polymer nanocomposites in the computer and electronics industry are investigated. These nanoparticles have received much attention from researchers and craftsmen, because graphene has unique thermal, electrical and mechanical properties. Its use as a filler in very small quantities substantially enhances the properties of nanocomposites. There are various methods for producing graphene-reinforced polymer nanocomposites. These methods affect the amount of graphene dispersion within the polymer substrate and the final properties of the composite. The application and the properties of graphene-reinforced polymer nanocomposites are discussed along with examples of results published in the papers. To better understand such materials, the applications of these nanocomposites have been investigated in a variety of fields, including batteries, capacitors, sensors, solar cells, etc., and the barriers to the growth and development of these materials application as suggested by the researchers are discussed. As the use of these nanocomposites is developing and many researchers are interested in working on it, the need to study and deal with these substances is increasingly felt.
... Toughening epoxy resin can be achieved by adding various organic or inorganic modifiers, such as liquid copolymers of butadiene and acrylonitrile with different terminal groups [4,5], thermoplastics [6,7], inorganic fillers [8][9][10][11], and hyperbranched polymers (HBPs) [12][13][14]. In order to meet the special optical requirements of display devices, modification processes cannot sacrifice the transmittance of materials. ...
... MWCNTs have excellent mechanical, electrical and structural properties and are able to form an electrical conductive network in a polymer matrix at much lower concentration than spherical particles [3][4][5][6]. Due to their properties like high aspect ratio and large specific area, MWCNTs were used to increase electrical conductivity of the coatings [7][8][9]. The addition of MWCNTs to polymer coatings can increase the corrosion resistance of the coatings which are formed from liquid compositions [10][11][12][13]. ...
In this work, two dispersing methods of multiwalled carbon nanotubes (MWCNTs) in polyurethane powder clear coatings based on a polyester resin and a blocked polyisocyanate were developed. TEM micrographs confirmed that additional sonication of MWCNTs in the polyester resin (before extrusion of the coatings) causes significantly better dispersion of the nanofiller in a polyurethane matrix in relation to a simple prepared without the sonification stage. Several properties of cured coatings were investigated such as roughness, gloss, adhesion to steel surface, cupping, hardness, scratch resistance, water contact angle, surface resistivity and corrosion resistance. The obtained results indicated that the water contact angle, electrical conductivity and the corrosion resistance of the PU coating were increased by the MWCNTs addition.
... The UV-irradiation was performed to develop the UV-polymerization, with 55 mw/cm 2 light intensity on sample surface for duration of 15 minutes and then 3 minutes for transparency of resin. The coatings of homogenous disc shaped nano-composite (thickness of 150 µm and diameter of 2 cm) were appeared [20]. Scheme 15: An IKA Ultraturrax (30000 rpm) was used for period of 10 minutes to disperse the carbon base nano fillers in ER. ...
Different schemes to photo-cure the epoxy resins (ER) are reviewed in this article. ER and photo initiator (PI) were mixed together and then mixtures were cured through a curing reaction which was proceeded in the presence of infrared or ultraviolet light (UV-Light), or an electron beam.
... Graphene, since its discovered, has drawn humans great attention for its unique mechanical, thermal, optical and electrical properties [1]. It's applications covered numerous fields, such as energy storage, sensor, composite, semiconductor, electrode, display, heat spreader and catalytic carrier [2][3][4][5][6][7][8][9]. Compared with other carbon forms (e.g., diamond, graphite, amorphous carbon, fullerenes and carbon nanotubes), graphene with superior performance continued to be a hot research area. ...
Chemical reduction of graphene oxide (GO) has been considered as a promising route towards the large scale production of graphene. Herein, a rapid, efficient photochemical method for preparing reduced graphene oxide (RGO) by ultraviolet (UV) irradiation of a mixture solution containing a photoinitiator and Monoethanolamine (MEA) compound in ethanol has been developed. In this route, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (GR-XBPO) was used as the reductant and MEA as the oxygen inhibition agent. After UV irradiation, oxygen-containing groups (OCGs) on GO plane and edges are being largely removed due to the reduction of GO by free radicals generated by photoinitiator decomposition. X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and ultraviolet and visible spectrophotometer showed that GR-XBPO can efficiently reduce GO at room temperature. It is also found that the electrical conductivity of RGO fabricated by this rapid route (~10 min) is more competitive compared to other reported works. Moreover the corresponding reduction mechanism was being discussed. This work puts forward a novel method for preparing graphene, and has great potential in scaling up graphene production and developing graphene materials.
... To realize a better dispersion of fillers, a number of methods have been developed. Currently, the three most widely used techniques for preparing composites including solution casting [4,5], melt mixing [6][7][8] and in situ polymerization [9,10]. The latter method requires extend processing time and organic solvent to mix the monomers and fillers; it is difficult to scale this technique to produce an industrially viable process. ...
Highly conductive graphite/acrylonitrile–butadiene–styrene copolymer (ABS) composites were prepared via foaming with supercritical carbon dioxide (scCO2), followed by de-foaming with an open mixing mill. This processing technique decreased the direct current resistivity of the composites by about 1 order of magnitude. The alternating current (AC) resistivity results demonstrated that an insulator-semiconductor transition occurred upon increasing the graphite content. In analyzing the AC impedance, it was shown that the response characteristics changed from capacitive to resistive at significantly lower graphite loading levels for composites processed with scCO2. The dispersion of graphite in the copolymer matrix was characterized by scanning electron microscopy (SEM), rheometry and dynamic mechanical analysis. SEM of graphite/ABS composites revealed that the graphite was very well-dispersed. The sample treated with scCO2 processing showed higher storage modulus and complex viscosity than those processed conventionally. Additionally, the Tg was increased by 2–3 °C after the scCO2 processing treatment. This approach to composites processing with scCO2 represents an attractive method for preparing electrically conductive composites with well-dispersed fillers.
... This can be related to the formation of a percolating path among CNTs that allows the electrical conduction [31], [49]. The reported values are comparable to those found in literature for bulky polymer and others nanofillers used [50]. ...
... It may be due to the fact that carboxylic acid groups loaded on the CNTs and carbon fiber surface reacted with epoxy groups of resin which increased the length of molecular chain segments. The increase of T g and decrease of tand for CF-CNTs/EP containing CNTs probably might be due to the enhancement of a restricted mobility interphase region composed of CNTs and epoxy [43]. ...
... Various analytical methods have been pursued to study the dispersion, interface, curing process and properties of GNPs based UV-curable nanocomposites [75,87,88]. To investigate the dispersion state of graphene within the polymer matrix, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM) have been widely used by Guo, Jaong and Eda et al. [8,10,11,81]. ...
... Various analytical methods have been pursued to study the dispersion, interface, curing process and properties of GNPs based UV-curable nanocomposites [75,87,88]. To investigate the dispersion state of graphene within the polymer matrix, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM) have been widely used by Guo, Jaong and Eda et al. [8,10,11,81]. ...
This chapter covers the preparation and properties of ultraviolet (UV)-curable nanocomposite containing carbon nanotubes as fillers. UV-curing technology is of particular interest due to its unique properties such as rapid curing process and solvent-free formulation. Alongside with the advantages of utilizing this curing method, carbon nanotubes undergo benefits including high aspect ratio, high transparency, and good mechanical properties. Carbon nanotubes (CNTs) are hollow cylindrical shaped configuration; consist of one, two, or more walls with an interlayer of non-covalent van der Waals force acting among the carbon atoms of various walls. Besides influencing the UV curing process, the CNTs loaded UV-curable nanocomposites sustain modified surface, thermal, mechanical, physical, and conductive properties which are discussed in this chapter. The health and safety concerns of using these classes of nanocomposite are further discussed.
... This technique was applied to produce graphene/polymers composites both with acrylates (by radical polymerization), and epoxides (by cationic way) obtaining nanocomposites with improved mechanical and electrical properties. 11,12 The aim of the present study is to investigate the water vapor barrier properties conferred to a photocured epoxy resin by low amounts of GO dispersed in it. ...
A transparent, water vapor barrier film made of an epoxy resin and graphene oxide (GO) was synthesized by photopolymerization process. The epoxy/GO film with just 0.05 wt% GO gives a 93% WVTR reduction with respect to the pristine polymer, reaching barrier properties better than other polymer composites containing higher amounts of graphene. The excellent water vapor barrier is attributed to the good dispersion of GO in the polymer matrix. Moreover, GO significantly enhances the toughness and the damping capacity of the epoxy resins. The hybrid film can have potential applications in anticorrosive coatings, electronic devices, pharmaceuticals and food packaging.
... Colored composites are reported in thin layers as effective depth of cure is very minute. 17,18 Bulky dimensions are reported through laborious ''layer-by-layer curing.'' Photo curing of complex shapes utilize complex lightening schemes, 19 i.e. robotically rotating threedimensional bulk matrixes or complex substrates moving through tunnel of lights. ...
In couple of years, epoxy UV curing has emerged as a necessity, yet it has some limitations, e.g. little curing conversion of thick films, especially with colored additives. Thick dimensions do not allow radiation to penetrate into the sample. Moreover, colored additives cover photoinitiators and reduce their efficiency. Therefore, UV-cured epoxy composites survive only in thin layers. Current research has resolved the issue, through a unique “smart approach,” which resolves the problem by separating the initiation step of the reaction (which is true photo-induced reaction) from the propagation (which is not directly dependent on light). This approach completely photo-cures epoxy thick films with colored additives. Superb filler dispersion has been observed, along with strongly interconnected polymeric network. Augmentation in thermo-mechanical properties has been observed through different instrumental techniques.
... This is complemented with the negative slope they present for the dielectric permittivity. This effect has been related to the Maxwell-Wagner-Sillars effect, which consists in the interface polarization of insulating polymer/ conductive filler for heterophasic systems [18,19]. The ability of TRGO for promoting the formation of an effective electrical percolation network when DTAB was used is evidenced by comparing the electrical properties of the resulting nanocomposites prepared by using this surfactant compared with those prepared with SDS. ...
The natural rubber (NR) latex consists of polymer particles charged negatively due to the adsorbed phospholipids and proteins molecules. The addition of stable aqueous suspension of thermally reduced graphite oxide (TRGO) stabilized by ionic surfactants to NR latex can favor the occurrence of interaction between the stabilized TRGO and NR particles. Herein, the use of two surfactants of different nature, namely, sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB), for the preparation of (TRGO)/NR nanocomposites, is reported. Zeta potential and particle size measurements indicated that the use of DTAB as cationic surfactant results in the flocculation of NR particles and promoted the formation of ion-pair interactions between TRGO and the proteins and/or phospholipids present on the NR surface. This indicates that the use of DTAB can promote a self-assembly phenomenon between TRGO with adsorbed DTAB molecules and NR particles. The occurrence of self-assembly phenomenon allows obtaining homogenous dispersion of TRGO particles in the polymer matrix. The TRGO/NR nanocomposites prepared by the use of DTAB exhibited superior mechanical properties and excellent electrical conductivities reaching values of stress at 500% strain of 3.02 MPa and 10
−4
S/cm, respectively.
The curing rate of epoxy resins is a critical parameter that significantly influences the curing properties of polymer matrix composites (PMCs). It plays a vital role in meeting high-performance requirements, particularly in achieving rapid development of high modulus. The paper reviews the current state of research on the curing of epoxy resins in PMCs, including theoretical studies on the curing kinetics of the curing rate. The effects of curing methods, curing agents, accelerators, functional fillers and composite curing processes on the curing rate and mechanical properties are also reviewed. In addition, the relationship between curing rate and mechanical properties of epoxy composites under different influencing factors is reviewed. The review aims to provide research ideas for obtaining advanced structural composites with fast curing and excellent mechanical properties.
This paper presents the results of dynamic mechanical analysis of carbon fiber reinforced nylon-66 nanofiber interleaved epoxy composites. The role of nylon-66 nanofiber has been investigated with specific reference to the percentage of interleaving with nylon-66 nanofibers. For a better understanding of the fiber matrix interactions, the composites were subjected to γ-irradiation, and the resulting changes in the dynamic mechanical properties due to nylon-66 interleaving and γ-irradiation are investigated and discussed. Nylon-66 interleaving and exposure of the composites to γ-irradiation are observed to influence the dynamic mechanical properties. The study has established that 1.15% of nylon-66 interleaving of the epoxy carbon fiber composite improves the Tg and it also leads to enhancement of the dynamic mechanical properties. Individually, the improvements in dynamic mechanical properties of the base were ll nylon-66 interleaved carbon epoxy composites due to γ-irradiation is observed to be minimal.
The present work aims at improving the barrier properties of high molecular weight Polyethylene/ graphene nanoplatelets (HMWPE/GnP) nanocomposites by aligning the embedded modified graphene nanoparticles in a magnetic field. Graphene nanoplatelets (GnP) were modified by magnetic Fe 2 O 3 to produce Fe 2 O 3 ‐modified Graphene, GnP‐mFe 2 O 3 . The magnetic properties of Fe 2 O 3 were previously characterized by the vibrating sample magnetometer (VSM) method and resulting GnP‐mFe 2 O 3 nanoparticles were characterized by Fourier transform infrared (FTIR) analysis. HMWPE/GnP nanocomposites were prepared via melt mixing. The prepared nanocomposites were sheeted at high temperatures in a magnetic field using a hot press. The barrier properties of prepared films, HMWPE/GnP and HMWPE/GnP‐mFe 2 O 3 were characterized by carrying out a permeation to oxygen experiment as a function of GnP and GnP‐mFe 2 O 3 contents. A decrease in gas transmission rate (GTR) was observed for the samples after being subjected to the magnetic field compared to the non‐treated sample. The results of differential scanning calorimetry (DSC) and field emission electron microscopy (FESEM) experiments confirmed the orientation of GnP‐mFe 2 O 3 nanoparticles in nanocomposites.
In this study, the influence of the tetraethylenepentamine (TEPA), covalently bound to the walls of graphene oxide (GO), on the thermal and mechanical properties of nanocomposites based on diglycidyl ether of bisphenol A (DGEBA)/graphene was investigated. The GO-TEPA nanosheets were synthesized in a fast reaction assisted by microwave radiation. The mixture of nanofiller with epoxy resin was carried out by roller mill in order to reach homogeneous dispersions. The morphology and properties of nanosheets of GO and GO-TEPA were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetry (TG/DTG) and Raman spectroscopy. Composites containing 0.1, 0.3 and 0.5 wt% of GO and GO-TEPA were prepared and improvements in the thermal and mechanical behavior of theses materials were observed. The composites were characterized by SEM, differential scanning calorimetry (DSC), nanoindentation, dynamic mechanical thermal analysis (DMA) and by the flash laser method. Nanoindentation measurements showed significant increases of up to 73% on Young's modulus and 140% on hardness for the composite containing 0.5 wt% GO-TEPA. The thermal conductivity measurements showed gains of up to 103% for composites compared to pure polymer. The thermal and mechanical performance of composites was corroborated by DMA and DSC measurements that showed increases of up to 20°C in the glass transition temperature (Tg). The good thermomechanical behavior of the composites strongly dependes on the degree of exfoliation and dispersability of nanofillers in the polymer matrix, which are associated with the extent of chemical modification of graphene nanosheets.
Alternative coating technologies based on advances in polymer engineering have been continuously developed to face the always present challenges of wear in metal surfaces. Fusion-bonded epoxy (FBE), an epoxy-based powder coating, has been widely used in some sectors due to its quick and easy application and the reduction of waste material. FBE is a high-performance composite with approximately 30 wt% microparticles, and the challenge addressed herein is to improve the coating properties by adding a low content of graphene. In this work, new coatings based on FBE and thermally reduced graphene oxide (rGO) were developed and prepared by two different processes: in one case, highly thermally stable and low functionalized graphene (rGO-tre with 4.6 % oxygenated groups) and in the other case, highly exfoliated and more functionalized graphene (rGO-tr with 9.8 % oxygenated groups). FBE/rGO-tr and FBE/rGO-tre nanocomposites were produced in concentrations of 0.1, 0.3, 0.5 and 1.0 wt% in a planetary ball mill. The coated steel plates were heated in a conventional oven at 204 °C, and the curing of the material was confirmed by using differential scanning calorimetry (DSC) analysis. The addition of rGO-tr (1.0 wt%) and rGO-tre (0.5 wt%) improved the adhesion of the nanocomposite coating in the wet test by 104 % and 95 %, respectively, when compared with neat FBE coatings. Small gains in abrasion and hardness were also observed. In addition to the tendency to reduce indentation (micro and nano), it was possible to observe a better recovery of the FBE with the addition of rGO-tr and rGO-tre after the deformation carried out by the tip. The integration of graphene nanofillers of different grades in a ternary composite with silicate microparticles and epoxy powder was successfully achieved, and the adhesion, abrasion and hardness benefit from the synergy between micro- and nanofillers.
Bio‐based photocurable polymers are increasingly demanded as environmentally friendly materials for advanced applications. Together with functional fillers, represent a next step for the generation of functional and active smart materials, compatible with additive manufacturing technologies. This work reports on, acrylated epoxidized soybean oil (AESO) mixed with different amounts of reduced graphene oxide (rGO) up to 6 wt.% in order to obtain UV‐curable piezoresistive and thermoresistive materials. It is shown that the addition of rGO to AESO hinders the curing process, but maintains always double bond conversions higher than 50%. Composites are characterized by a good dispersion of micrometric filler clusters. Further, the thermal stabilities are close to 300°C and cross‐linking degrees are above 1.75 mmol·cm–3. The Young modulus of the composites decreases with the addition of the rGO fillers, in particular for the higher filler contents, and electrical conductivities up to 0.13 S·m–1 are obtained for the composites with the highest rGO content. UV‐curable composites with piezoresistive and thermoresistive responses suitable for applications are thus obtained, characterized by gauge factors around 26 for deformations up to 2% and maximum thermoresistive sensitivity of S = 0.43, similar values to the values obtained for petroleum‐based materials. This article is protected by copyright. All rights reserved
Nanocomposites integrate functional nanofillers into viscoelastic matrices for electronics, lightweight structural materials, and tissue engineering. Herein, the effect of methacrylate-functionalized (MA-SiO2) and vinyl-functionalized (V-SiO2) silica nanoparticles on the thermal, mechanical, physical, and morphological characteristics of poly(ethylene glycol) (PEG) nanocomposites was investigated. The gel fraction of V-SiO2 composites decreases upon addition of 3.8 wt% but increases with further addition (>7.4 wt%) until it reaches a plateau at 10.7 wt%. The MA-SiO2 induced no significant changes in gel fraction and both V-SiO2 and MA-SiO2 nanoparticles had a negligible impact on the nanocomposite glass transition temperature and water absorption. The Young's modulus and ultimate compressive stress increased with increasing nanoparticle concentration for both nanoparticles. Due to the higher crosslink density, MA-SiO2 composites reached a maximum mechanical stress at a concentration of 7.4 wt%, while V-SiO2 composites reached a maximum at a concentration of 10.7 wt%. Scanning electron microscopy, transmission electron microscopy, and small-angle X-ray scattering revealed a bimodal size distribution for V-SiO2 and a monomodal size distribution for MA-SiO2. Although aggregates were observed for both nanoparticle surface treatments, V-SiO2 dispersion was poor while MA-SiO2 were generally well-dispersed. These findings lay the framework for silica nanofillers in PEG-based nanocomposites for advanced manufacturing applications.
The viscoelastic materials exhibit different tribological responses when compared to the stiff materials, due to the intermediate mechanical properties between viscous liquid and elastic solid. In this work, the effect of damping materials viscoelasticity on sliding friction under dry condition was investigated. However, it was difficult to change its damping properties only while other properties (strength or surface hardness) remain unchanged, since viscoelasticity was one of its intrinsic properties. Therefore, the attention of interactions between the material components was closely paid. To achieve this, the experimental groups of damping materials with various viscoelasticity were established by adding various fillers and adjusting their surface properties. Additionally, a viscoelastic property determined friction coefficient model was obtained and validated by the molecular dynamic method. The results show that the test model is in good agreement with the experimental results. Meanwhile, tribo-pairs with higher proportion of viscous character had greater oscillations in friction. They also exhibited higher friction coefficient due to the increased contribution of viscoelastic hysteresis losses to friction.
A new method of grafting multi-walled carbon nanotubes (MWCNTs) onto carbon fiber surface to improve the thermo-mechanical properties of woven carbon fabric reinforced composites was proposed. In this method, both carbon woven fabrics and MWCNTs were oxidized by sulfuric acid to generate carboxyl groups on their surfaces, respectively. Then silane coupling agent was used to react with the carboxyl groups to graft MWCNTs onto the carbon fiber surfaces of the woven fabric. The untreated, acid treated and MWCNTs grafted carbon woven fabrics were separately combined with polypropylene films to form composite plates by thermal-stamping. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were conducted to estimate the changes of element contents and functional groups on surfaces of carbon fibers and MWCNTs. Atomic force microscope was used to estimate the roughness of carbon fiber surfaces. Scanning electron microscopy, differential scanning calorimeter, dynamic mechanical thermal analysis and tensile tests were carried out to analyze the surface morphology, thermal, and mechanical properties of carbon fabrics and their composites. Testing results showed that MWCNTs could be successfully grafted onto the carbon fibers by using silane as an intermediate bridge. Compared with the untreated and acid treated composites, the in-plane shearing stiffness and fracture strength of the composites were increased significantly by MWCNTs grafting. In terms of thermal properties, acid treatment and MWCNTs grafting have little effect on melting point of composites. MWCNTs can promote the recrystallization process of the PP and reduce the numbers of imperfect crystals. As for thermo-mechanical properties, acid treatment deteriorated the bending storage modulus of the composite, while MWCNTs grafting could compensate it.
Traditionally, most synthetically developed materials are hardened by heating them to an elevated temperature, a process requiring large amounts of energy and space. Interest in photo cured materials using UV-light is growing due to simplifications in manufacturing and growing environmental concerns; it is expected photocuring could reduce electricity consumption by 90% compared to traditional curing. Photocured materials also reduce evaporation of volatile organic components, curing time and waste, thereby enhancing productivity and reducing work space.
The materials technologies based on photocuring are gaining momentum, and this will be the first book to provide an in-depth focus on the subject. This book summarises the fundamentals required to understand the field, characterises the use of novel materials and the development of synthetic aspects, and discusses the future of the technology.
The comprehensive review chapters are suitable for a broad readership from diverse backgrounds including chemistry, physics, materials science and engineering, medical science, pharmacy, biotechnology and biomedical engineering. Photocured Materials will be of interest to students, researchers, scientists, engineers and professors.
Epoxid-Kohlenstofffaser-Prepregs finden in der zivilen Luft- und Raumfahrtindustrie aufgrund ihrer hervorragenden mechanischen, thermo-mechanischen und thermischen Eigenschaften zunehmend Anwendung zur Herstellung von Strukturverbundbauteilen. Obwohl Kohlenstofffasern elektrisch leitfähig sind, weisen aus Epoxid-Kohlenstofffaser-Prepreg hergestellte Bauteile aufgrund der isolierenden Natur der Epoxidmatrix oft nur sehr geringe elektrische Leitfähigkeiten in z-Richtung auf. Die verbesserte elektrische Leitfähigkeit in z-Richtung ist jedoch für moderne Verbundanwendungen notwendig, bei denen ein gewisses Maß an elektrostatischer Ableitung, elektromagnetischer Abschirmung oder eine verbesserte Widerstandsfähigkeit gegen Blitzeinschläge erforderlich ist. Die vorliegende Arbeit beschäftigt sich hauptsächlich mit der Untersuchung des Einflusses leitfähiger Rußnanopartikel auf die elektrische Leitfähigkeit und die Bruchzähigkeit eines für die Luft- und Raumfahrt relevanten Epoxidharzes und seiner unidirektionalen Kohlenstofffaser Prepreg-Laminate. Die Beziehung zwischen dem Faservolumengehalt und der elektrischen Leitfähigkeit der reinen Laminate wurde umfassend charakterisiert. Darüber hinaus wurde der Einfluss eines PA6.6-Vlieses auf die elektrischen und mechanischen Eigenschaften der Laminate detailliert erforscht. Schließlich wurde die Korrelation zwischen der elektrischen Leitfähigkeit (in z-Richtung) und der Beständigkeit gegen Blitzschlag von mit PA6.6-Vlies modifizierten Laminaten untersucht.
The full potential of poly(L-lactide) (PLLA) reinforced with graphene oxide, GO, nanocomposites tends to be hindered by aggregation of the nanofillers. In order to promote a good dispersion of GO in the PLLA matrix, polymer grafting techniques have been explored to anchor PLLA onto functionalized GO surface to produce GO-PLLA hybrids. For this purpose, PLLA with a terminal triple bond was synthesized by ring-opening polymerization. By controlling the concentration of monomer to initiator, PLLA samples with three different chain lengths have been prepared and later coupled to azide-functionalized GO using click chemistry. These hybrids were then mixed with commercial PLLA and cast films have been prepared. The ensuing nanocomposite films were studied using Depth Sensing Indentation and the results have shown that PLLA matrix-filler interaction can be modulated by controlling the chain length of PLLA graft. This is a critical point because the enhancement of these interactions provides a stronger matrix-filler interphase which improves the stress transfer between both phases and increases the contribution of the interphase to the stiffening of the nanocomposites. Therefore, it has been proven that judicious functionalization of GO is an effective procedure for improving the strength, the stiffness and the creep resistance of the PLLA composites.
The aim of this research was to develop the UV-cured epoxy/carbon composites. The rheological properties of the uncured neat epoxy and epoxy composite with graphite, graphene, and multi-walled carbon nanotube (MWCNT) were evaluated to observe the macroscopic flow behavior and the microstructure by shear force. The results showed that epoxy/carbon composites at high filler content exhibited shear-thinning behavior with a high yield stress value and epoxy/MWCNT at 30 phr showed this characteristic obviously. The fractured surface and particle dispersion in the epoxy matrix were evaluated by scanning electron microscopy and transmission electron microscopy, respectively. Epoxy/carbon composites at high filler content displayed rough fracture surface with particle agglomeration, thus the electrical conductivity increased. The result showed that the epoxy/MWCNT composites had high potential to use as a conductive adhesive with a 3D printing process due to high electrical conductivity with high viscosity that could be formed easily during processing.
In this study, three epoxy thermosetting materials possessing polyoxyethylene units are prepared starting from polyethylene glycol. To improve the mechanical strength of the epoxy materials, alongside the flexible units of polyoxyethylene, rigid aromatic and alicyclic moieties arised from two popular monomers are also present into the structures obtained. Thus, epoxide-functionalized polyoxyethylene (EFPOE) and/or diglycidyl ether of bisphenol A (DGEBA) are cured by amine-functionalized polyoxyethylene (AFPOE) and/or isophorone diamine (IPDA). The formulas of EFPOE:DGEBA/AFPOE:IPDA (A), EFPOE/IPDA (B), and DGEBA /AFPOE (C) are stoichiometrically used. To reinforce thermal and thermo-mechanical behaviors, three epoxy networks (D, E, and F) with the same formulas but loaded by 0.5 wt.% of Jeffamine-modified graphene oxide (GO) nanoplatelets are also prepared. In the binary epoxy-amine systems for preparing A and D networks, both resins and hardeners are taken in equimolar amounts. In other systems, leading to B, C, E and F networks, either resin or hardener, just one, is based on polyoxyethylene unites. Heat stability, ultimate tensile strength, elongation at break, and storage moduli (E' values) of the neat epoxy networks as well as the GO-loaded ones were measured and compared with each other. It was found that the epoxy/GO networks, especially that of prepared using binary epoxy-amine systems (network D), have superior thermal properties and greater values of storage modulus (E') around Tg and higher temperatures.
This chapter deals with various types of lubricating polymer nanocomposite coatings and their syntheses, characterization, and performance evaluation. It also establishes the critical parameters in nanocomposite lubrication, lubrication mechanism, and application with future outlook.
We employed an easy and direct method to measure the thermal conductivity of epoxy in the liquid (nanofluid) and solid (nanocomposite) states using both rodlike and platelet-like carbon-based nanostructures. Comparing the experimental results with the theoretical model, an anomalous enhancement was obtained with multiwall carbon nanotubes, probably due to their layered structure and lowest surface resistance. Puzzling results for functionalized graphene sheet nanocomposites suggest that phonon coupling of the vibrational modes of the graphene and of the polymeric matrix plays a dominant role on the thermal conductivities of the liquid and solid states.
PACS: 74.25.fc; 81.05.Qk; 81.07.Pr.
Graphene-based materials are single- or few-layer platelets that can be produced in bulk quantities by chemical methods. Herein, we present a survey of the literature on polymer nanocomposites with graphene-based fillers including recent work using graphite nanoplatelet fillers. A variety of routes used to produce graphene-based materials are reviewed, along with methods for dispersing these materials in various polymer matrices. We also review the rheological, electrical, mechanical, thermal, and barrier properties of these composites, and how each of these composite properties is dependent upon the intrinsic properties of graphene-based materials and their state of dispersion in the matrix. An overview of potential applications for these composites and current challenges in the field are provided for perspective and to potentially guide future progress on the development of these promising materials.
This work presents a novel approach to the functionalization of graphite nanoparticles. The technique provides a mechanism for covalent bonding between the filler and matrix, with minimal disruption to the sp2 hybridization of the pristine graphene sheet. Functionalization proceeded by covalently bonding an epoxy monomer to the surface of expanded graphite, via a coupling agent, such that the epoxy concentration was measured as approximately 4wt.%. The impact of dispersing this material into an epoxy resin was evaluated with respect to the mechanical properties and electrical conductivity of the graphite–epoxy nanocomposite. At a loading as low as 0.5wt.%, the electrical conductivity was increased by five orders of magnitude relative to the base resin. The material yield strength was increased by 30% and Young’s modulus by 50%. These results were realized without compromise to the resin toughness.
Graphene has attracted the attention of a growing number of scientists from several disciplines due to its remarkable physical properties and chemical functionalisation capabilities. This review presents an overview of graphene/polymer nanocomposites discussing preparation, properties and potential applications. The challenges and outlook of these emerging polymer nanocomposites are also discussed.
In this article we report the successful manufacture of a novel functionalized graphene sheet (FGS)/silicone porous nanocomposite. Both the cellular microstructure and the properties of the porous nanocomposite were investigated in detail. The thermal properties show great stability and heat dissipation efficiency, highlighting their potential in applications with intense thermal requirements. Additionally, compression measurements indicate that there was a favourable interaction between the graphene nanosheets and the polymer.
In this study, the mechanical properties of epoxy nanocomposites with graphene platelets, single-walled carbon nanotubes, and multi-walled carbon nanotube additives were compared at a nanofiller weight fraction of 0.1 +/- 0.002%. The mechanical properties measured were the Young's modulus, ultimate tensile strength, fracture toughness, fracture energy, and the material's resistance to fatigue crack propagation. The results indicate that graphene platelets significantly out-perform carbon nanotube additives. The Young's modulus of the graphene nanocomposite was approximately 31% greater than the pristine epoxy as compared to approximately 3% increase for single-walled carbon nanotubes. The tensile strength of the baseline epoxy was enhanced by approximately 40% with graphene platelets compared to approximately 14% improvement for multi-walled carbon nanotubes. The mode I fracture toughness of the nanocomposite with graphene platelets showed approximately 53% increase over the epoxy compared to approximately 20% improvement for multi-walled carbon nanotubes. The fatigue resistance results also showed significantly different trends. While the fatigue suppression response of nanotube/epoxy composites degrades dramatically as the stress intensity factor amplitude is increased, the reverse effect is seen for graphene-based nanocomposites. The superiority of graphene platelets over carbon nanotubes in terms of mechanical properties enhancement may be related to their high specific surface area, enhanced nanofiller-matrix adhesion/interlocking arising from their wrinkled (rough) surface, as well as the two-dimensional (planar) geometry of graphene platelets.
Conventional liquid phase oxidation of multiwall carbon nanotubes (MWCNTs) using concentrated acids generates contaminating debris that should be removed using aqueous base before further reaction.
Graphite intercalation compounds are a new class of electronic materials that are classified as graphite-based host guest systems. They have specific structural features based on the alternating stacking of graphite and guest intercalate sheets. The electronic structures show two-dimensional metallic properties with a large variety of features including superconductivity. They are also interesting from the point of two-dimensional magnetic systems. This book presents the synthesis, crystal structures, phase transitions, lattice dynamics, electronic structures, electron transport properties, magnetic properties, surface phenomena, and applications of graphite intercalation compounds. The applications covered include batteries, highly conductive graphite fibers, exfoliated graphite and intercalated fullerenes and nanotubes.
This work presents the preparation of functionalized graphene sheets (FGS)/epoxy coatings cured by cationic photopolymerization with enhanced mechanical properties. The kinetics of the photopolymerization process for formulations up to 1.5 wt% of graphene were evaluated by means of Real-Time FTIR spectroscopy. The reinforcement of the cured coatings by the graphene was studied by measuring the dynamic-mechanical properties and the surface hardness. An increase of almost 40 °C in the Tg was obtained by adding 1.5 wt% of graphene to the epoxy matrix. A good dispersion state and interaction of the graphene with the matrix were observed by TEM and FESEM analyses.
The present investigation compares different carbon-based nanoscaled materials with regard to their effectiveness in producing thermoplastic polymers with antistatic and electrically conductive behavior. The dispersed phases are carbon black (CB) as spherical particles, multiwalled carbon nanotubes (MWNT) as fiber-like filler, and expanded graphite (EG) as platelet-like filler. Each was incorporated into polycarbonate by small-scale melt mixing. The electrical percolation concentrations were found to be 2 wt% for MWNT, 4 wt% for EG, and 8.75 wt% for CB which parallels the aspect ratios of the fillers. For EG a strong dependence of morphology and electrical resistivity on mixing time was observed, indicating a structural change/destruction during intensive shear mixing. Rheological percolation thresholds were found to be lower than electrical percolation threshold for the MWNT and CB, but similar in the case of EG. The general impact on complex melt viscosity decreases in the order MWNT, CB, EG. For EG, at higher loadings (above 4wt%) the viscosity increase with filler content is delayed as is the decrease in resistivity.
The properties of graphite intercalation compounds (GIC's) are discussed with respect to possible applications. Five families of intercalates give high electrical conductivity to GIC's: pentafluorides leading to high conductivity, 108 S/m (higher than metallic copper); metal chlorides; fluorine and alkali metals with bismuth giving relatively high conductivity of the order of 107 S/m plus stability in air; and residual halogens showing extremely high stability under severe conditions, though the conductivity is only of the order of 106 S/m. Electrodes of different GIC's have been tried in primary and secondary batteries, where their characteristics are high electrical conductivity and easy diffusion of electrochemically active species between the graphite layers. Primary lithium batteries of a covalent graphite fluoride are now widely used commercially. Secondary batteries using different host graphites and intercalates give interesting results. Large amounts of hydrogen can be stored in the functional space in alkali metal-GIC's. The same GIC's show high coefficients of isotope separation of hydrogen at liquid nitrogen temperature. The structure and texture of the host graphite play a decisive role in the absorption and separation behaviors of GIC's. Exfoliated graphite prepared by rapid heating of GIC's or their residue compounds leads to flexible graphite sheets which have great industrial applications. Some problems connected with the production and use of these sheets are discussed.
Dielectric measurements are reported on a series of model sandwich structures which mimic heterophase polymer systems which have been studied in an attempt to explore the possible use of this technique for morphological characterization. The model system consists of a polycarbonate sheet into which have been introduced a large number of small diameter holes, which are in turn filled with air, poly(ethylene oxide), and triflate-doped poly(ethylene oxide). A comparison is made between the dielectric behavior of this model system and that of a similar structure in which the same volume fraction of the conducting phase is incorporated in terms of a single hole. Measurements are also reported on pure poly(ethylene oxide) in the form of pressed and molded disks. In all cases, good agreement was found between the predictions of the simple Maxwell-Wagner-Sillars theory and experimental observation. This study illustrates the potential of dielectric measurements in the investigation of conducting occlusions in a nonconducting matrix and opens up the possibility of the investigation of heterophase systems.
Antistatic epoxy coatings are obtained, for the first time, by cationic UV curing of an epoxy resin in the presence of a very low content of carbon nanotubes (CNTs). It is shown that the addition of only 0.025 wt.‐% of CNTs into the resin is sufficient to obtain a composite suitable for applications that require electrostatic discharge. An extended percolative structure that forms a conductive CNT network is clearly evidenced within the polymeric matrix, notwithstanding the very small CNT content. The use of such UV‐cured epoxy material systems for antistatic coatings is quite realistic and promising.
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Multi-walled carbon nanotube (MWCNT)/high density polyethylene (HDPE) and graphene nanosheets (GNS)/HDPE composites with a segregated network structure were prepared by alcohol-assisted dispersion and hot-pressing. Instead of uniform dispersion in polymer matrix, MWCNTs and GNSs distributed along specific paths and formed a segregated conductive network, which results in a low electrical percolation threshold of the composites. The electrical properties of the GNS/HDPE and MWCNT/HDPE composites were comparatively studied, it was found that the percolation threshold of the GNS/HDPE composites (1 vol.%) was much higher than that of the MWCNT/HDPE composites (0.15 vol.%), and the MWCNT/HDPE composite shows higher electrical conductivity than GNS/HDPE composite at the same filler content. According to the values of critical exponent, t, the two composites may have different electrical conduction mechanisms: MWCNT/HDPE composite represents a three-dimensional conductive system, while the GNS/HDPE composite represents a two-dimensional conductive system. The improving effect of GNSs as conducting fillers on the electrical conductivity of their composites is far lower than theoretically expected.
The effect of the incorporation of single-walled carbon nanotubes (SWNTs) onto a diglycidyl ether of bisphenol A-based (DGEBA) epoxy resin cure reaction was investigated by thermal analysis and Raman spectroscopy. The results of the investigation show that SWNTs act as a strong catalyst. A shift of the exothermic reaction peak to lower temperatures is, in fact, observed in the presence of SWNTs. Moreover, these effects are already noticeable at the lowest SWNT content investigated (5%) with slight further effects at higher concentrations, suggesting a saturation of the catalyzing action at the higher concentrations studied. The curves obtained under isothermal conditions confirm the results obtained in nonisothermal tests showing that the cure reaction takes less time with respect to the neat epoxy. The thermal degradation of cured DGEBA and DGEBA/SWNT composites was examined by thermogravimetry, showing a faster thermal degradation for DGEBA–SWNT composites. Raman spectroscopy was successfully applied to demonstrate that the observed changes in the cure reaction of the composites lead to a different residual strain on the SWNT bundles following a different intercalation of the epoxy matrix. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 452–458, 2003
An in situ polymerization was conducted in the presence of expanded graphite obtained by rapid heating of the graphite intercalation compound (GIC) to form a polymer/expanded graphite conducting composite. Study showed that the graphite was dispersed in the form of nanosheets in the polymer matrix. The transition from an electrical insulator to an electrical semiconductor for the composite occurred when the expanded graphite content was 1.8 wt %, which was much lower than that of conventional conducting polymer composite. The composite exhibited high electrical conductivity of 10−2 S/cm when the graphite content was 3.0 wt %. This great improvement of conductivity could be attributed to the high aspect ratio (width-to-thickness) of the graphite nanosheets. Study suggested that extensive rolling of the blend greatly affected the conductivity of the composite. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2506–2513, 2001
This paper examines the recent advancements in the science and technology of carbon nanotube (CNT)-based fibers and composites. The assessment is made according to the hierarchical structural levels of CNTs used in composites, ranging from 1-D to 2-D to 3-D. At the 1-D level, fibers composed of pure CNTs or CNTs embedded in a polymeric matrix produced by various techniques are reviewed. At the 2-D level, the focuses are on CNT-modified advanced fibers, CNT-modified interlaminar surfaces and highly oriented CNTs in planar form. At the 3-D level, we examine the mechanical and physical properties CNT/polymer composites, CNT-based damage sensing, and textile assemblies of CNTs. The opportunities and challenges in basic research at these hierarchical levels have been discussed.
Flexible polyurethane (PU) foams, with loading fractions of up to 0.2 wt% carbon nanotubes (CNTs), were made by free-rising foaming using water as blowing agent. Electron microscopy revealed an open cellular structure and a homogeneous dispersion of CNTs, although the incorporation of nanofiller affected the foaming process and thus the final foam density and cellular structure. The compressive response of the foams did not show an unambiguous improvement with CNT content due to the variable foam structure. However, dense films generated by hot pressing the foams indicated a significant intrinsic reinforcement of the polymer, even at low loadings of CNTs. Most significantly, CNTs were found to increase the acoustic activity monotonically at concentrations up to 0.1 wt%.
Composites based on graphene-based sheets have been fabricated by incorporating solution-processable functionalized graphene into an epoxy matrix, and their electromagnetic interference (EMI) shielding studies were studied. The composites show a low percolation threshold of 0.52 vol.%. EMI shielding effectiveness was tested over a frequency range of 8.2–12.4 GHz (X-band), and 21 dB shielding efficiency was obtained for 15 wt% (8.8 vol.%) loading, indicating that they may be used as lightweight, effective EMI shielding materials.
We review experimental and theoretical work on electrical percolation of carbon nanotubes (CNT) in polymer composites. We give a comprehensive survey of published data together with an attempt of systematization. Parameters like CNT type, synthesis method, treatment and dimensionality as well as polymer type and dispersion method are evaluated with respect to their impact on percolation threshold, scaling law exponent and maximum conductivity of the composite. Validity as well as limitations of commonly used statistical percolation theories are discussed, in particular with respect to the recently reported existence of a lower kinetic (allowing for re-aggregation) and a higher statistical percolation threshold.
Nanostructured modification of polymers has opened up new perspectives for multi-functional materials. In particular, carbon nanotubes (CNTs) have the potential to realise electrically conductive polymers with improved or retaining mechanical performance. This study focuses on the evaluation of both, the electrical and thermal conductivity of nanoparticulate filled epoxy resins. We discuss the results with regard to the influence of the type of carbon nanotube (SWCNT, DWCNT and MWCNT), the relevance of surface-functionalisation (amino-functionalisation), the influence of filler content (wt% and vol%), the varying dispersibility, the aspect ratio and the specific surface area.
Current theories suggest that multiwalled nanotubes may form through a scrolling mechanism ([1][1], [2][2]). The concept that scrolling could lead to nanotube-like structures ([3][3]) inspired us to extend our recent work on making colloidal suspensions of layered compounds ([4][4]) to graphite.
A process is described to produce single sheets of functionalized graphene through thermal exfoliation of graphite oxide. The process yields a wrinkled sheet structure resulting from reaction sites involved in oxidation and reduction processes. The topological features of single sheets, as measured by atomic force microscopy, closely match predictions of first-principles atomistic modeling. Although graphite oxide is an insulator, functionalized graphene produced by this method is electrically conducting.
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