No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Study of the crosslinking process of waterborne UV curable polyurethane acrylates
Abstract
UV curable acrylic end capped polyurethane dispersions were obtained by the acetone process, using different molecular weight polyols. Photo Differential Scanning Calorimetry (Photo-DSC) was employed to study the effect of the photoinitiator concentration as well as the curing temperature in the curing reaction rate. The penetration capacity of UV radiation was determined by “in situ” Attenuated Total Reflectance Infrared Spectroscopy (ATR-FTIR). In addition, Temperature Modulated Differential Scanning Calorimetry (TM-DSC) was used to calculate the crosslinking degree through the measurement of the Heat Capacity (Cp). According to Photo-DSC data, the conversion of the curing reaction increased with temperature and no dependence with the photoinitiator concentration was found. Cp values of the cured samples enabled us to compare the crosslinking degree as a function of photoinitiator concentration, polyol molecular weight and curing temperature.
... Finally, acetone is removed under vacuum to obtain a WPU dispersion that can give rise to a free-radical type UV curing step. Typically, the urethane dispersion has a pH 7-8 and a solids content of 30-40 wt.%, remaining stable for several months [32]. Since the viscosity of polymeric dispersions is dependent on the concentration and particle size of the chains, it is possible to obtain systems with viscosities suitable for specific applications [33]. ...
... From the 138 reviewed papers, twenty-seven (27) used polytetramethylene glycol (PTMG) as polyol [26,. Polypropylene glycol (PPG) was the second most chosen polyol, being part of twenty two studies [12,23,32,40,52,59,65,[67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82], followed by poly(ethylene glycol) (PEG) (sixteen studies) [7,21,73,[83][84][85][86][87][88][89][90][91][92][93][94][95][96], poly(ε-caprolactone) (PCL) (thirteen studies) [6,20,31,52,59,[97][98][99][100][101][102][103][104][105], polyether diol (twelve studies) [22,[106][107][108][109][110][111][112][113][114][115][116][117], polycarbonate diol (PCD) (ten studies) [24,33,52,103,[118][119][120][121][122][123][124], and hyperbranched aliphatic polyester (HBP) (nine studies) [11,[125][126][127][128][129][130][131][132][133], vegetable oil (castor, linseed or cardanol) (six studies) [134][135][136][137][138][139], as well as a mixture of two polyols [65,140,141]. Other polyols were also reported [9,40,73,103,[142][143][144][145][146][147][148][149][150][151][152]. ...
... The hardness, curing rate, and conversion on the photopolymerization increased with the decrease in the polyol's molar mass, mainly because dispersions based on shorter chain polyols have greater reactivity. A higher relative concentration of methacrylate double bonds in the system forms stronger polymer networks [24,32,56]. Although a higher crosslink density leads to better physical performance, elongation at break is reduced considerably with crosslinking [24,50,118]. ...
Waterborne polyurethane coatings prepared by UV-induced photoreactions (UV-WPU) are becoming very attractive due to the increasingly stringent environmental demands. They were developed to replace solvent-based polyurethanes in the coatings of wood, paper, plastics, metal, and glass, mainly because of their good physicochemical, rheological, and optical properties. Several UV-WPU formulations have been tested over the years, making their research substantial. However, no valuable review of this literature, focusing on the significant influencing factors in UV-WPU's manufacture, is available to date. This work aims to answer specific questions about the state of these materials' art, such as: "which monomers have been used most in UV-WPU synthesis?", "what type of photo-initiator has promoted the most efficient curing of the material?", "what additives or particles have been tested for composite UV-WPUs?", "which applications have UV-WPUs been directed to?", "what adaptations and technologies have already been tested to overcome the challenges of the process?", among others. As a result of a systematized bibliographic search in four databases, considering the period from January 2000 to July 2020, a total of one hundred and thirty-eight distinct and relevant articles on UV-WPUs were found. From this study, we hope to present a scientific source on the current state-of-the-art of UV-WPU synthesis, providing new combinations of raw materials and intelligent solutions, thus making material and industrial engineers able to mitigate the inconveniences of the process.
... Most of commercial thermal curable water-borne PUs have low hardness, abrasion resistance and solvent resistance properties compared to thermal cured solvent-based PUs. On the other hand, UVcurable water-borne polyurethane acrylates (WPUAs) have higher abrasion resistance and adhesion on textiles and other surfaces, flexibility, gloss, hardness, scratch and chemical resistance due to their acrylate modified and specific segmented structure (Liorente et al., 2016;Li et al., 2018). PU is a segmented polymer basically comprises from soft (polyether or polyester polyols) and hard segments (diisocyanate and chain extender) and is obtained by a polyaddition reaction between the polyol and diisocyanate (Piotr, 2000;Tielemans et al., 2006). ...
... Then, TEA and BD were added into flask as a neutralizing agent and a chain extender respectively. DBTDA (800 ppm) and acetone were fed together with TEA and BD (Liorente et al., 2016). The TEA was added to dispersion to neutralize carboxylic acid with 1:1 molar ratio of DMPA to TEA (Zhu et al., 2019). ...
... T g values of cured polymeric films of PPG-3 and PEG-3 formulations were higher than those of PPG-C and PEG-C formulations (Table 6) since the curing process reduced the chain mobility of PPG-3 and PEG-3 binders in a (G€ und€ uz, 2015). This result can be related to relatively higher methacrylate double-bound density in PPG-3 and PEG-3 binders synthesized with PPG 1000 and PEG 1000 polyols respectively, resulting in a higher polymerization rate (Liorente et al., 2016) and as a consequence higher hardness value (Figures 6-8). ...
Purpose
In this study, it is aimed to synthesize ultraviolet (UV)-curable water-borne polyurethane acrylate (WPUA) binders using different types of polyols (poly (propylene glycol), PPG 1000 and PPG 2000 and poly (ethylene glycol), PEG 1000 and PEG 2000 ) at different molecular weights, DMPA (2,2-bis(hydroxymethyl) propionic acid) at different amounts and isophorone diisocyanate (IPDI) and use for pigment printing on synthetic leather.
Design/methodology/approach
UV-cured films were characterized by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimeter (DSC). The effect of binder structure on printing performance was determined with hardness, crock fastness, abrasion resistance and color measurements.
Findings
The highest abrasion resistance (60,000 cycles) and crock fastness values (dry crock and wet crock: 3/4) were obtained with binder PEG-C synthesized with PEG 2000 and lower DMPA amount of 4.89 wt%; however, PEG-C binder showed lower hardness values. Due to lower urethane groups in PEG-C binder, more flexible films were obtained which imparted good adhesion property to printing film. Synthesized binders provided lower crock fastness and abrasion resistance properties than commercial WPUA binder.
Originality/value
Pigmented formulations including UV-curable water-borne synthesized PUA binder were developed and for the first time applied onto synthetic leather using screen printing method. Within this context, a new environmentally friendly printing method was proposed in this study including binder synthesis in the preparation of printing formulations.
... Recently, our group has studied the UV crosslinking process of radiation curable polyurethane acrylates obtained from non-renewable polyols [36]. The present work is devoted to introducing renewable polyols in these types of systems in order to obtain more sustainable UV curable polyurethane dispersions. ...
... It should be noted that the Dp values were higher than those presented by WPUs containing similar DMPA amounts but obtained from non-bio-based polyols [36]. This result can be explained upon the basis of the lower polarity of the bio-based polyols. ...
... Finally, it is worth mentioning that both the conversion and polymerization rate values reached with polyurethanes synthesized from dimer fatty acid diols were slightly lower in comparison with those reported in literature for non-biobased polyols [36]. This result could be related with the semicrystalline nature of the dimer fatty acid polyols used in the present work. ...
In the last few years there has been a great deal of interest in modifying the methodologies for obtaining polyurethanes using more sustainable strategies. Following this tendency, in the present work, waterborne UV-curable polyurethanes were synthesized using commercially available dimer fatty acid based polyols obtained from renewable resources (Priplast from Croda). The polyols, characterized by proton nuclear magnetic resonance (¹H NMR), differential scanning calorimetry (DSC) and size exclusion chromatography (GPC–SEC), were semicrystalline and presented very broad melting related with their complex molecular weight distribution. Different polyurethane dispersions were obtained by changing the percentage of the hard segment. Comparing with waterborne polyurethane dispersions obtained from non-renewable resources, the dispersions showed higher particle size even using similar or higher amounts of internal emulsifier. The curing behaviour was characterized by photo-differential scanning calorimetry (Photo-DSC) and the results showed that the conversion and polymerization rate decreased with the hard segment content and temperature. The obtained products displayed good thermal characteristics with phase-separated structures.
... NCO-terminated urethane prepolymer highly reactive compound and capped by hydroxyalkyl acrylate formed vinyl-terminated PU. Various end-capping agents which are used widely in the production of PUA are 2-hydroxyethyl acrylate (HEA) [10,12,16,19,22,23,27-31,33,34,48,60-62,66,70,77,84,88,93,96-99, 106,110,113,123,125,126,127,129,131,132,137,143] , 2-hydroxyethyl methacrylate (2-HEMA) [3,14,17,21,26,27,35,36,38,40,42,45,46,48,49,51,52,61,65,67,73,75,79,81,104,119,120,121,133,136,139,141] , pentaerythritol tri-acrylate (PETA) [17,26,48,63,91,92,135] . Hydroxyl-functionalized acrylate monomer, such as telechelic polyol acrylate and multifunctionalized acrylate, also use [103] , hydroxybutyle methacrylate (HBMA) [85,117] , acrylamide [46] hydroxypropyle methacrylate [83] and dodecafluoroheptyl methacrylate (DFMA) [139] used as a fluorine acrylate monomer. ...
... The conversion degree of double bonds increased with increasing incident light intensity due to the penetration of light intensity [152] . Higher molecular weight of polyol's low conversion in comparison to low molecular weight of polyols due to low concentration of double bonds in same processing condition of PUA [14] . Similarily, Qin et al. [23] observed that the conversion percent increased with increasing molecular weight of alcohols (octadecan-1-ol > hexadecane-1-ol > n-octanol > n-butanol), this may be due to the reduction of double-bond density formed less cross-link networks in the PUA. ...
... The double bond present at the chain ends of PUA could be polymerized by thermal or free radical initiators as well as by exposure to ultraviolet [12][13][14] , electron beam [70,145] , laser [154] , and microwave. A typical representation for curing of the PUA is shown in Figure 18. ...
Polyurethane-acrylate (PUA) oligomers are a new class of polyurethane (PU) which produced by the reaction of polyols with diisocyanate and capped by acrylate. There is a growing demand for modification with improved properties of the PUA. This review covers the following topic: structure, modification of PUA backbone, reactive diluents, curing, mechanical, optical, thermal behavior and applications are presented herein. The basic understanding of the chemistry and mechanistic aspect of these oligomers has a reached a level was tailor made formulations suitable for a particular application may be selected.
... An increase of viscosity may also explain this limitation of conversion. Overall, the obtained conversion values are in consistency with those of PUAs systems [1,2,43]. ...
... Figs. 3 and 4 display typical TGA curves and their first derivative curves giving T max (temperature at maximum degradation rate) of each step. As for conventional polyurethanes [8,43], thermal degradation of NIPUA coatings occurs in two-steps, with degradation of the hard segment parts (HS, T max ≈ 320°C) followed by the PTMO soft segment parts (SS, T max ≈ 410°C). The A-C6-2000 prepolymer revealed similar two-step degradation profiles. ...
Non-isocyanate polyurethane acrylate coatings (NIPUAs) were prepared by photocrosslinking of mixtures of an acrylate terminated NIPU oligomers (A-Ol) and reactive (meth-)acrylate diluents. A-Ol were prepared by a transurethane polycondensation pathway followed by an acrylation reaction of the resulting hydroxy chain-ends. The influence of the reactive diluent content and chemical structures on the thermal and mechanical properties of these coatings has been investigated. The obtained materials exhibited thermal stabilities above 255°C, Young modulus ranging from 2.6 to 9.2 MPa, tensile strength from 2.69 to 25.5 MPa and elongation at break from 56 to 470 %.
... The most commonly used are 2-hydroxyethyl acrylate [6], 2-hydroxyethyl methacrylate [2], but also pentaerythritol tri-acrylate [7], which allows for higher cross-linking density. The synthesis of WPUA is usually performed using a diluent, most often acetone, due to the high viscosity of the mixture [8]. Prior to the application of VOC free water dispersion, the acetone must be evaporated, which increases the cost of the synthesis. ...
UV-curable poly(urethane-acrylate) cationomer coatings modified with 3(3-(propoxy-2-ol-)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide)-3-propyloxy),1,1,1,3,5,5,5-heptamethyltrisiloxane (HMTS-AGE-DOPA) containing phosphorus and silicon atoms were obtained. The structures of the compounds were characterized by nuclear magnetic resonance (NMR) and Fourier-transform infrared (FT-IR) spectroscopy. The influence of HMTS-AGE-DOPA on the thermal properties and flame retardancy of the materials was investigated. Some surface properties (gloss, contact angle, surface free energy) and performance properties (hardness, abrasion resistance) of the modified coatings were investigated. The introduction of HMTS-AGE-DOPA reduced the glass transition temperature and increased thermal stability. With the addition of the modifier, a significant decrease in the total heat release (THR) was observed. The gloss of the coatings was very high (above 90 GU at all angles), although it slightly decreased with increasing content of the modifier. The introduction of HMTS-AGE-DOPA caused an increase in the hydrophobicity of the coatings due to the presence of siloxane moieties. The coatings are medium-hard materials with a Persoz hardness in the range of 0.38-0.47. The introduction of the modifier resulted in a slight reduction in hardness and an increase in abrasion resistance.
... One of the most useful methods employed to overcome this drawback involves the crosslinking of the material during the film formation process. For this purpose, several methods are utilized such as the introduction of high functionality monomers [3], and the functionalization of the polyurethane chains with acrylic double bonds or with alkoxysilane groups [4,5]. In the latter, alkoxysilane hydrolysis and condensation reactions take place during the drying process giving rise to an organic/inorganic hybrid polymer network with improved mechanical and thermal properties. ...
Waterborne polyurethane (WPU) dispersions were prepared for flame retardant coatings. Specifically, alkoxysilane-capped polycaprolactone-based WPUs were synthesized employing the acetone process, and Casein, as a green and sustainable flame retardant additive, was added by two different methods (in situ and ex situ). These two strategies made possible to evaluate the effect of the Polyurethane/Casein interaction in the final properties of the dispersions and films. FTIR and solid-state ²⁹Si NMR, confirmed the formation of the siloxane network during film generation process. The addition of Casein during the synthesis (in situ) resulted in a covalent bonding between the polyurethane and Casein, which significantly increased the particle size. However, the incorporation after phase inversion of the WPU (ex situ), did not change the particle size. Tensile tests revealed that the covalent bond promoted an increase in the brittleness of the material compared to ex situ approach due to a better dispersion of the Casein in the system. TGA results showed that Casein increased the thermal stability of all the coatings, especially of those obtained by the ex situ route. Moreover, and according to the microscale combustion calorimeter (MCC) and vertical burning test (UL-94) measurements Casein delayed the combustion of the material. Consequently, due to their characteristics, these Casein-WPU dispersions could potentially be used as combustion retardant coatings, where good physicochemical properties are essential for effective performance.
... 10 The incorporation of MWCNT into the PUA polymer matrix affects the UV curing process at a wavelength of 395 nm due to its light absorption and reduced the T g of PU, which also further reduced both acrylic C]C double bond conversion and photopolymerization rate due to the competition of light adsorption with the photoinitiator 10,131 and high conversion at the immobilization of the polymer chains caused by the UV curing reaction. 10,132 The decrease in the T g was due to the nanollers' plasticizing effect that led to a larger free volume within the polymer with increasing MWCNT content. 10,133 Nevertheless, the uniform dispersion of the MWCNT enhanced the electrical conductivity due to the low electrical percolation thresholds, 10,134 while it still maintained the mechanical properties of the PUA matrix. ...
Stimuli responsiveness has been an attractive feature of smart material design, wherein the chemical and physical properties of the material can be varied in response to small environmental change. Polyurethane (PU), a widely used synthetic polymer can be upgraded into a light-responsive smart polymer by introducing a light-sensitive moiety into the polymer matrix. For instance, azobenzene, spiropyran, and coumarin result in reversible light-induced reactions, while o-nitrobenzyl can result in irreversible light-induced reactions. These variations of light-stimulus properties endow PU with wide ranges of physical, mechanical, and chemical changes upon exposure to different wavelengths of light. PU responsiveness has rarely been reviewed even though it is known to be one of the most versatile polymers with diverse ranges of applications in household, automotive, electronic, construction, medical, and biomedical industries. This review focuses on the classes of light-responsive moieties used in PU systems, their synthesis, and the response mechanism of light-responsive PU-based materials, which also include dual- or multi-responsive light-responsive PU systems. The advantages and limitations of light-responsive PU are reviewed and challenges in the development of light-responsive PU are discussed.
... WPU is a kind of typical viscoelastic material, which has certain characteristics of viscous fluid and elastic solid [39,40]. Firstly, Fig. 8a and a′ shows the change Content courtesy of Springer Nature, terms of use apply. ...
Waterborne polyurethane (WPU) prepolymer with acrylate terminal was prepared by using hydroxyethyl acrylate as an end-capping agent. Modified gelatin (mGH) was prepared by grafting vinyl groups which were obtained from hydrolysis and condensation of vinyl trimethoxysilane onto the renewable natural polymer material cold-water fish skin gelatin. Due to the excellent biodegradability and mechanical properties of cold-water fish skin gelatin, mGH was introduced into the WPU backbone by covalent bonding to improve WPU comprehensive property. The vinyl groups in mGH and the acrylate ends in the WPU prepolymer were connected by UV curing to prepare biodegradable and renewable mGH/WPU chemical hybrid materials. The test results showed that the film-forming properties, the water resistance and thermal stability of WPU were improved by covalent bonding. Water contact angle increased from79.6° to 96.5°, and the maximum thermal degradation rate temperature increased from 340 to 400 °C. In addition, incorporation of mGH with high modulus improved the moduli and yield strength of WPU, in which the yield strength increased from 11.3 to 18.2 MPa. The degradation performance of mGH/WPU chemical hybrid materials was also evaluated that the degradation rate reached 68% in 0.6% lipase PBS solution and 56% in soil after 60 days. The study provides a novel polymerization method for preparing high biodegradable decorative coatings and prints of specialty metals, polymer plastics and certain types of woodware as well as medical scaffold materials.
Graphical abstract
... At present, there has been limited work on polyurethane acrylate coating using UV-LED since most of them employed the UV-mercury curing system [15,[31][32][33][34][35][36][37]. Strongone et al. [38] and Malluceli [39] reported the possibility to prepare a UV-LED curable nanocoating based on epoxy acrylate with enhanced thermal and mechanical properties. ...
The elimination of mercury, low energy consumption, and low heat make the ultraviolet light-emitting diode (UV-LED) system emerge as a promising alternative to conventional UV-mercury radiation coating. Hence, a series of hydrophobic coatings based on urethane acrylate oligomer and fluorinated monomer via UV-LED photopolymerisation was designed in this paper. The presence of fluorine component at 1160 cm−1, 1235 cm−1, and 1296 cm−1 was confirmed by Fourier Transform Infra-Red spectroscopy. A considerably high degree C=C conversion (96–98%) and gel fraction (95–93%) verified the application of UV-LED as a new technique in radiation coating. It is well-accepted that fluorinated monomer can change the surface wettability as the water contact angle of the coating evolved from 88.4° to 121.2°, which, in turn, reduced its surface free energy by 70.5%. Hence, the hydrophobicity of the coating was governed by the migration of the fluorine component to the coating surface as validated by scanning electron and atomic force microscopies. However, above 4 phr of fluorinated monomer, the transparency of the cured coating examined by UV-visible spectroscopy experienced approximately a 16% reduction. In summary, the utilisation of UV-LED was a great initiative to develop green aspect in photopolymerisation, particularly in coating technology.
... The final step comprises the extraction of the organic solvent. The acetone process enables controlling the molecular weight, and particle size and distribution with high reproducibility, considering that the polymer synthesis is carried out in a homogeneous solution [20,36]. In fact, the acetone dilution avoids viscosity constraints, being recovered to be reintroduced in the system. ...
Polyurethanes and polyurethane-ureas, particularly their water-based dispersions, have gained relevance as an extremely versatile area based on environmentally friendly approaches. The evolution of their synthesis methods, and the nature of the reactants (or compounds involved in the process) towards increasingly sustainable pathways, has positioned these dispersions as a relevant and essential product for diverse application frameworks. Therefore, in this work, it is intended to show the progress in the field of polyurethane and polyurethane-urea dispersions over decades, since their initial synthesis approaches. Thus, the review covers from the basic concepts of polyure-thane chemistry to the evolution of the dispersion's preparation strategies. Moreover, an analysis of the recent trends of using renewable reactants and enhanced green strategies, including the current legislation, directed to limit the toxicity and potentiate the sustainability of dispersions, is described. The review also highlights the strengths of the dispersions added with diverse renewable additives, namely, cellulose, starch or chitosan, providing some noteworthy results. Similarly, dispersion's potential to be processed by diverse methods is shown, evidencing, with different examples, their suitability in a variety of scenarios, outstanding their versatility even for high requirement applications.
... Indeed, A-Ol with molecular weight around 2000 g/mol (C c=c > 2.0 meq/g) exhibited high conversion (χ > 90%), whereas A-Ol with molecular weight around 5000 g/mol (C c=c > 0.7 meq/g) exhibited lower conversion (χ ≈ 75%). These conversions are in good agreement with the values in the literature for conventional PUAs systems [1,2,32]. In order to discuss the crosslinking properties of the prepared films, respect to the theoretical functionality of the precursor A-C6-650/TMP-1/0.5 (f = 2,33), according to the following equation: ...
A transurethane polycondensation pathway has been used to produce acrylate terminated Non-Isocyanate PolyUrethane (NIPUA) oligomers (A-Ol) with controlled molecular weights and chemical structures. These compounds were then photo-crosslinked under UV radiations to afford several NIPU acrylate coatings. The influence of the content in urethane functions as well as the chemical structures on the thermal and mechanical properties of the final coatings has been demonstrated. The obtained coatings exhibited thermal stabilities above 255 °C, Young modulus ranging from 2.6 to 9.2 MPa, tensile strength up to 11.8 MPa and elongation at break varying from 20 to 520%.
... After chain extension reaction, adequate amount of water is introduced to obtain CWPU. 40-60% of acetone is added to reduce the viscosity during chain extension reaction, which is removed once the CWPU is successfully prepared [13]. Compared with acetone process, prepolymer mixing process is conducted by dispersing the hydrophilic prepolymer into water, followed by chain extension using the diamine as chain extender. ...
Intrinsic cross-linked waterborne polyurethane (CWPU) was successfully synthesized for the first time through solvent-free condensation polymerization, in which green castor oil (CO) was used as the cross-linking agent. The totally solvent-free process was realized by using hydrophilic polypropylene glycol as hydrophilic segment, which was synthesized by the esterification of polypropylene glycol with pyromellitic dianhydride. The effect of CO content in the soft segment of the prepared CWPU on emulsion properties was investigated by laser particle size distribution test, and the prepared CWPU emulsion showed uniform size distribution (0.117–0.275 µm) and milky white appearance after storing at ambient temperature for 6 month. Additionally, the effect of CO content in CWPU films on static mechanical properties, dynamic mechanical properties, hydrophilicity and thermal stability was also studied by tensile test, dynamic mechanical analysis, water absorption and contact angle measurement as well as thermogravimetric analysis. The prepared cross-linked CWPU films have good stability and outstanding mechanical strength (11.94–34.51 MPa), making them adequate supplement for the conventional waterborne polyurethanes.
... These radicals initiate the polymerization process leading to the formation of a cross-linked solid coating. As a recent example, Llorente et al. [2] studied the crosslinking process of waterborne UV-curable polyurethane acrylates depending on the concentration of photoinitiator and the temperature of the curing process. UV-curable coatings present multiple advantages: low activation energy, low curing temperature (even room temperature curing) and high hardness of the final coating [1]. ...
In this work, a thermoset ultraviolet (UV)-cured polyurethane-acrylate resin was doped with different chemically-modified graphene obtained from a commercial graphene oxide (GO): as-received GO, chemically reduced GO (rGO), GO functionalized with vinyltriethoxysilane (VTES) (GOvtes), and GO functionalized with VTES and subsequently reduced with a chemical agent (rGOvtes). Modified graphene was introduced in the oligomer component via solvent-assisted process using acetone, which was recovered after completion of the process. Results indicate that the GO-doped oligomers produce cured coatings with improved anti-scratch resistance (above the resistance of conventional coatings), without surface defects and high transparency. The anti-scratch resistance was measured with atomic force microscopy (AFM). Additionally, results are presented in terms of Wolf–Wilburn scale, a straightforward method widely accepted and employed in the coating industry.
... 50 Moreover, a small band of $1649 cm À1 attributed to the C]C stretching vibration peak in acrylic was observed. 51 ...
UV curable waterborne polyurethane acrylate (WPUA) with surfactant-modified TiO2/reduced graphene oxide (TiO2/rGO) nanocomposites were prepared and analyzed to improve their mechanical performance and self-cleaning ability. TiO2/rGO nanocomposites were prepared by a simple hydrothermal method with nano-TiO2 and graphene oxide, and modified with cationic surfactant (CTAB) to obtain a cationic TiO2/rGO (C-TiO2/rGO). Then, the obtained C-TiO2/rGO was incorporated into anionic waterborne polyurethane acrylate by in situ fabrication to obtain a composite emulsion (C-TiO2/rGO-WPUA). The results of Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) showed that CTAB was successfully intercalated into TiO2/rGO, and TiO2 nanoparticles were evenly distributed on graphene sheets with good dispersibility. Compared to UV-cured neat WPUA and C-TiO2/rGO-WPUA, the mechanical properties and thermal stability of the composites were significantly improved. When the content of C-TiO2/rGO was 0.5%, the UV-cured composites had overall excellent performance. In particular, the WPUA composites exhibited good self-cleaning ability in photocatalysis. The photocatalytic degradation rate of methyl orange in 0.5% C-TiO2/rGO-WPUA reached 88.3% under 6 h visible light irradiation.
... For improving the properties like solvent resistance and mechanical strength of WPUs, increasing cross-linking density is an effective way. [12,13] Internal cross-linking agents, such as trifunctional trimethylol propane, [13] silane coupling agent, [14] and hydroxyethyl acrylate, [15] are introduced into chain of WPUs as chain extender or capping agents via covalent bonds through the synthesis procedure of WPUs. Although Internal cross-linking agents show excellent compatibility with WPUs and enhancement in the properties, time-consuming and complex synthesis procedure of internal-cross-linked WPUs limited its wide application. ...
Hydroxyl‐terminated cationic waterborne polyurethanes (HCWPUs) were synthesized using N‐methyldiethanolamine (N‐MDEA) as internal emulsifier and mixed with cross‐linker of nonionic waterborne blocked polyisocyanate (NWBI) to prepare cathodic electrodeposition (CED) coatings. The effects of N‐MDEA content, NCO/OH molar ratio, neutralization degree, and NWBI content on the performance of HCWPUs emulsion and relevant CED coatings were investigated. The results showed that 7.5 wt.% of N‐MDEA content, 0.9/1 of NCO/OH molar ratio, and 100% of neutralization degree were the optimal experimental parameter for synthesizing excellent performance HCWPUs. Incorporation of nonionic waterborne blocked isocyanate could significantly promote the hardness, adhesion, and solvent resistance of CED coatings without influencing the emulsion stability and coatings thermostability.
... . For Membrane 2# (PAA 5k 0.2 wt%) , 4# (PAA 5k 0.5 wt%) , 7# (PAA 50k 0.2 wt%) and 9# (PAA 50k 0.4 wt%) , the PVP in the separation layers was effectively crosslinked, thus the T g of PVP in Membrane 2#, 4#, 7# and 9# was increased obviously. In comparison, the crosslinking degree of PVP was increased with the increase of PAA content from 0.2 wt% to 0.4 wt% (Chen et al., 2014; Fiejdasz et al., 2013), but decreased with the increase of the PAA molecular weight from 5 kDa to 50 kDa (Fiejdasz et al., 2013;Llorente et al., 2016). The lower molecular weight and higher content of PAA were in favor of the increase of the separation layer crosslinking degree. ...
... At present, the water soluble photosensitive resin is the most important component in UV-curing coating material and it mainly includes unsaturated polyester, polyurethane acrylate (PUA), polyacrylate, and polyester acrylate [9]. By comparison, the preparation of WUVCW by the PUA resin as the pre-polymerization system has been reported [10]. Gloss is an important indicator of the optical properties of the coating [11]. ...
A waterborne ultraviolet (UV)-curing coating was prepared on the surface of wood materials with modification of talcum powder and calcium carbonate (CaCO3). When the waterborne UV-curing coatings on the surface of wood materials (WUVCW) was radiated for 1 min by UV (λ = 365 nm) and dried at 40 °C for 10 min, it showed good hardness, adhesion, and impact strength, with controlling the talcum content of 2.0% and CaCO3 content of 1.0%, respectively. When the content of talcum powder was higher than 2%, the mechanical properties and gloss of the WUVCW decreased, and when the talcum powder of WUVCW increase to more than 5%, a matte surface appeared after curing. When CaCO3 and talcum powder were present at the same time, the mechanical properties of WUVCW were better than those of only CaCO3 or talcum powder.
... The stretching vibration absorption peak at 3385 cm -1 is assigned to -NH-, and the peak at 1722 cm -1 belongs to C-O-C (ester bond), which reflecting the formation of urethane groups (-NHCOO-). Meanwhile, the peak at 2270 cm -1 ascribed to the characteristic absorption of -NCO is observed [27,28]. In Fig. 3b, the peak at 2270 cm -1 is disappeared, which illustrates that the -NCO has reacted with the -OH completely. ...
Enhancing the dispersion stability and self-antibacterial properties of cationic waterborne polyurethane materials is of vital importance to its various applications. In this work, a novel UV-curable waterborne polyurethane with pendant amine (PWPU) from 4-NCO prepolymer and modified by guanidinoacetic acid (GAA) was prepared by a simple method. The 4-NCO prepolymer is originated from the progressively grafting of tridentate polycaprolactone. The GAA, which is rarely used in coating industry, plays a positive reinforced role in our self-antibacterial coatings. Taking fully advantage of the merits of pendant amine and GAA, PWPU without bactericides possesses excellent properties in gram-negative (92.05%) and gram-positive (94.77%) antibacterial tests. Compared with the linear amine waterborne polyurethane (LWPU), PWPU has significant superiority in stability, and the increase in antibacterial efficiency is about 50%. Moreover, antibacterial efficiency still maintained 87.94% after 12 times washing. AFM results display that GAA and pendant amine increase the hydrophilic groups of coating surface, which improves the antibacterial performance. The experiments of thermal, mechanical performance and chemical resistance proof the reliability of the coatings. Therefore, this work has large potential in the applications of antibacterial materials.
A series of two-component UV-curable waterborne CO2-based polyurethane dispersions (UV-PUDs) with excellent flexibility and mechanical strength were synthesized from poly(propylene carbonate) diol (PPCD), isophorone diisocyanate (IPDI), 2,2-bis(hydroxymethyl) propionic acid (DMPA), 2-hydroxyethyl acrylate (HEA), pentaerythritol triacrylate (PETA) and 1,4-butanediol (BDO). One component was UV-curable waterborne polyurethane terminated by HEA and PETA (molar ratio 1:1), and the other component was linear waterborne polyurethane. The content of the UV-curable component in UV-PUD was 15%, 30%, 45%, 60%, and 100% (weight content). The obtained cured films exhibited superior flexibility without loss of tensile strength, accompanied by excellent acid and alkali resistance. In particular, the dried UV-PUD films without curing showed good mechanical properties.
Dispersion of graphene in water-based epoxy resins has always been a challenge. In this work, the stable and uniform graphene oxide modified emulsifying epoxy resin curing agents (WPA@GOs) were firstly prepared by intercalation polymerization. Subsequently, WPA@GO was used to emulsify E44 to obtain WPA@GO/E44 nano-emulsions. Compared to WPA/E44 and WPA-GO/E44, the water resistance, tensile strength, and anticorrosive properties of WPA@GO/E44 were significantly increased. The corrosion density of WPA@GO2/E44 coating decreased by 5 times and polarization impedance increased by 10 times in comparison to WPA/E44 coating.
Polyurethane (PU) is a widely used polymer material in many sectors. It has a high industrial value for metal corrosion protection as a coating material. Recently, it has also been considered an inhibitor to protect the metal's inner surface from corrosion in different corrosive mediums. The corrosion can be suppressed by using the proper content of PU inhibitor. The key advantage of this inhibitor is its ability to anchor certain protective functional groups onto the metal surface. The anchoring of functional groups onto the surface is not opposed in the presence of a highly corrosive medium. Thus, the PU is recently considered an immerging inhibitor in the industry. This chapter provides the synthesis, properties, and performance of PU as a corrosion inhibitor in the corrosive medium.
The silane coupling agent modified SiO2 particles, multi aperture silica aerogel and waterborne polyurethane acrylate (WPUA) were blended to produce resin coated fabrics with good thermal stability, to achieve excellent water repellency and a certain protective property. The thermal stability and water repellency of ordinary cotton could be improved by the hydrophobic SiO2 particles, WPUA and silica aerogel (SA) powders on the fabric surface. Our experimental results illustrated that the thermal stability of the coated fabric was greatly improved by adding aerogels and silane modified SiO2, and the amount of residual carbon increased significantly at 600 °C as the corresponding residues of SA/WPUA coated fabric finally could be 13.19%. The water contact angle of the fabric was obviously increased after the silane modified SiO2 particles mixed with SA/WPUA. It was found that the more aerogel added, the larger the contact angle was, and the contact angel reached about 120° when the aerogel was 4 wt%. It could be proved that the coated fabric had a certain surface self-cleaning effect. The tensile tests characterized that the stress of the coated fabric reached the maximum value of 64 MPa when the aerogel dosage was 2 wt%. Chemical resistance analysis suggested that the fabric had similar chemical resistance after the integration of porous aerogel particles. However, unlike most polyurethane coatings, the majority of chemicals were adsorbed in aerogel coatings. The infrared spectrum of the coating samples showed that the coating surface was stable, which was attributed to the interfacial adhesion between cotton fiber and polyurethane adhesive. The appearance of aerogel and SiO2 particles dispersed on the fabric surface was analyzed by SEM. All outcomes indicated a significant improvement in general properties of WPUA coatings by adding a handful of silica aerogel (0.5–4 wt%).
A novel UV-curable waterborne polyurethane-acrylate (WPUA) was firstly prepared based on hydroxyl telechelic natural rubber (HTNR) via sequential emulsion polymerization. The WPUA was composed of HTNR, Hexamethylene diisocyanate (HDI), 2-hydroxyethyl acrylate (HEA), and the content of hydroxymethyl propionic acid (DMPA) was studied for effects on particle size, stability, and morphology of the new series of WPUA dispersions. The WPUA had a good stability at a total solids content of about 20%. Particle size and dispersion stability slightly decreased with DMPA content. The WPUA gave a good film formation and can provide good wettability with high surface free energy. The mechanical and thermal properties of WPUA film were improved by UV-curing. The effects of photoinitiator (Darocur1173) content were investigated. The UV-cured WPUA films showed better mechanical properties and less water absorption than the not cured WPUA film. Also, the surface wetting was the improvement in the water resistance of the coating on the substrate. In addition, the thermal properties by TGA and the dynamic properties by DMTA slightly increased with photoinitiator dose level due to the higher crosslink density and decreasing the molecular weight between crosslink (Mc) caused the Tg shift to a higher temperature.
Waterborne polyurethanes (WPU) are of great importance in the industrial field as adhesives and coatings due to the reduced use of organic solvents in their formulations. However, one of the main drawbacks of these formulations is their high hydrophilic character, so in this work siloxane groups were introduced into the soft segment in order to solve this problem. Thus, the synthesis of polyurethane dispersions with different proportions of the polyols (poly-ε-caprolactone (PCL) and polydimethylsiloxane (PDMS)) was carried out following the acetone process in three stages: polyurethane synthesis, water dispersion of the polymer and acetone removal. The reactions were monitored by Infrared Spectroscopy (FTIR) and the particle size was determined by Dynamic Light Scattering (DLS). Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Size Exclusion Chromatography (SEC), and Proton Nuclear Magnetic Resonance (¹H NMR) were used to characterize the polyurethanes. Finally, after coating the dispersions onto metal substrates, adhesion strength, contact angle and phase morphology were studied. The introduction of siloxane as soft segment increased the surface roughness and hydrophobicity but did not change the adhesion values.
In this paper, a series of UV-curable waterborne polyurethane–acrylate (WPUA) emulsions were synthesized by using isophorone diisocyanate (IPDI) as the hard segment, polybutylene adipate glycol (PBAG) and different dosages of hydroxyl-terminated polydimethylsiloxane (HTPDMS) as the soft segment, 2,2-dimethylolpropionic acid (DMPA) as hydrophilic chain extender, and pentaerythritol triacrylate (PETA) as the blocking agents. The properties of the WPUA emulsions were then characterized by using Fourier transform infrared spectrometry, Zeta potential analysis, dynamic light scattering, and UV-cured films were characterized through Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, scanning electron microscope, UV–vis spectrophotometer, and thermogravimetric analysis, as well as by measuring the contact angle of water, testing the water absorption. The results indicated that with increasing HTPDMS content in the WPUA, the particle size of the emulsion was increased significantly, while the absolute value of Zeta potential was increased slightly. The resistance of WPUA cured film to water was increased. The ultimate water absorption declined from 11.12 % to 6.81 % and the equilibrium time of water absorption extended from 50 h to more than 100 h. When the HTPDMS content of WPUA was 10.0 wt%, the water contact angle of the cured film was the largest at 114°, which indicated that the surface of the cured film has been changed from a hydrophilic surface to a hydrophobic one. Thermogravimetric analysis results showed that the initial decomposition temperature of WPUA film gradually increased with adding of HTPDMS, performing better thermal stability.
Photocurable thermochromic and humidity responsive materials based on polyurethane acrylated (PUA) and bis(1-butyl-3-methylimidazolium) tetrachloronickelate ([Bmim]2[NiCl4]) ionic liquid (IL) have been prepared with varying IL content up to 40 wt.% within the polymer matrix. The influence of IL content on the photopolymerization process, morphology, Young modulus and electrical conductivity of the materials was evaluated. All materials present a total polymer conversion of at least 88%. The presence of the IL influences the morphology of PUA, being observed a porous network structure upon IL incorporation into the PUA matrix. All samples show a Tg around room temperature, which is independent of the IL content and a Young modulus that decreases with the IL content. All composites exhibit humidity dependent thermochromism from colourless to blue. Further, the influence of the relative humidity in the colour change was accessed for the sample containing 20 wt.% [Bmim]2[NiCl4], being observed that the colour variation is thermally activated and humidity governed, being 55% the minimum value of the relative humidity for colour change to occur.
The increased demand of electronic devices promotes the development of advanced and more efficient energy storage devices, such as batteries. Lithium-ion batteries (LIBs) are the most studied battery systems due to their high performance. Among the different battery components, the separator allows the control of lithium ion diffusion between the electrodes. To overcome some drawbacks of liquid electrolytes, including safety and environmental issues, solid polymer electrolytes (SPEs) are being developed. In this work, a UV photocurable polyurethane acrylate (PUA) resin has been blended with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) up to 30 wt% LiTFSI content to reach a maximum ionic conductivity of 0.0032 mS/cm at room temperature and 0.09 mS/cm at 100 °C. Those values allowed applying the developed materials as photocurable SPE in Swagelok type Li/C-LiFePO4 half-cells, reaching a battery discharge capacity value of 139 mAh.g⁻¹ at C/30 rate. Those results, together with the theoretical studies of the discharge capacity at different C-rates and temperatures for batteries with LiTFSI/PUA SPE demonstrate the suitability of the developed photocurable SPE for LIB applications.
Taking into consideration environmental issues and additive manufacturing technologies, the development of advanced UV curable polymers and polymer composites is an area of increasing interest. In this scope, polyurethane acrylate (PUA) composites with Indium Tin Oxide (ITO) were produced in order to tune morphology, optical, thermal, mechanical and dielectric properties. It is shown that ITO particles are well dispersed within the polymer matrix and that the polymerization rate and the UV curing conversion degree are influenced by the ITO content. Moreover, the optical transparency has decrease to 20% for the samples containing 10 wt% ITO content and the elastic modulus increases 10% for same sample. On the other hand, the glass transition temperature of PUA is independent of the ITO amount. ITO/PUA composites with 25 wt% ITO filler content presents high dielectric constant of 33. This composite has been used for developing a capacitive sensor, showing the suitability of the UV curable materials for capacitive sensing applications.
This book presents the proceedings of IBEREO 2019. This conference addresses the most recent trends in rheology with a special emphasis on both basic science and industrial applications. Papers presented cover different perspectives, like experimental, theoretical and numerical. Topics include Microfluidics and microrheology, Food, Cosmetics and Pharmaceutical Products; Suspensions and Colloids; Rheometry and Experimental Methods; and Polymers and Biopolymers.
The aim of the present work is to increase the sustainability of UV curable waterborne polyurethane dispersions using the Diels-Alder chemistry. In this way, the obtaining of crosslinked polyurethane coatings presenting healing and recycling properties is proposed.
Thus, waterborne polyurethanes were obtained by the acetone process replacing the chain extender by a diol containing the Diels Alder adduct and using acrylic chain ends that allowed the UV cross-linking. Photo-DSC results showed that the Diels Alder adduct did not prevent the UV cross-linking of the coating. In addition, FTIR, DSC and rheological experiments confirmed the occurrence of the DA and retro DA reaction (at 60 °C and 120 °C respectively) in the cross-linked polymer. Thanks to this reaction, the materials obtained by this methodology could be healed and reprocessed when increasing the temperature as shown by the maintenance of the mechanical properties and carbon dioxide permeability after repairing. These results can be of great interest towards the development of more sustainable waterborne polyurethane coatings.
Polymer-based composites are increasingly used for the development of stimuli responsive smart and multifunctional materials. Most of those materials are obtained from solvent-based processes, but the use of solvents represents usually induce non-desirable environmental issues and waste generation. Thus, UV-curable materials, processed at room temperature, without solvent emissions and with high energy efficiency, represent an interesting alternative to overcome these issues. In this work, polyurethane acrylate (PUA) UV-curable resins have been used for the development of composites with multi-walled carbon nanotubes (MWCNT) with suitable morphological, thermal, mechanical, electrical and piezoresistive properties for sensor applications. The inclusion of MWCNT into the PUA polymer matrix affects the UV curing process due to their light absorption and decreases the glass transition temperature. A good dispersion of the MWCNT is obtained for the lower filler concentrations leading to a mechanical reinforcement and an increase of the electrical conductivity. The electro-mechanical response of the MWCNT/PUA composites at and above the percolation threshold is characterized by gauge factors around 2 for deformations up to 5%, providing their suitability for force and deformation sensing applications.
When performing extensional ER tests for the characterization of electro-rheological fluids, the time between applying the electric field and triggering the experiment (delay time) plays an important role in ER behaviour of the sample. The current study investigates the delay time effect in extensional ER characterization. The ER sample used in the measurements is a suspension of cornstarch in olive oil with a concentration of 30 wt%. Fixtures adaptable to the commercial version of the Capillary Breakup Extensional Rheometer (HaakeTM CaBERTM, Thermo Scientific) are designed and fabricated to allow the application of an external electric field aligned with the flow kinematics undergone by the fluid sample while the extensional characterization is taking place. An in-house code developed in Matlab is used to process the images and investigate the filament thinning behaviour of the sample under 3 kV applied voltage and at different delay times (0 s, 10 s, and 40 s).
The goal of tissue engineering is to repair damaged tissues. It is based on three important factors: cells, growth factors and scaffolds. The scaffolds are porous matrices which serve as a platform for cell adhesion and offer the ideal environment for the release of cells and so, their growth. In addition, the scaffold must keep its integrity until the tissue formed has suitable mechanical properties. Among the possible materials used for the development of scaffolds, two biopolymers can be highlighted: a protein such as collagen and a polysaccharide such as chitosan, which provide enormous biocompatibility. One of the challenges in these scaffolds is to provide the appropriate rheological properties during their use. To achieve it, an additional crosslinking process is carried out, to produce bonds between different biopolymer chains. These bonds can be produced in two different ways: chemical and enzymatic pathways. The results show that it is possible to develop scaffolds with enhanced mechanical properties and optimal porosity by modifying the initial composition used.
The introduction of additive manufacturing (AM) techniques is revolutionizing the field of polymer processing, as it provides a unique alternative to produce three-dimensional shapes and highly personalized structures. [1] Among different (AM) techniques, Vat photopolymerization, material jetting and binder jetting technologies rely on photo cross-linkable resins. Thus, Photo rheometry has gained attention as it appears as an essential tool to understand the material behaviour in the process and the development of new feedstock materials. In essence, photo rheometry measurements permit to analyse rheological behaviour of materials during photochemical processes, mainly cross-linking reactions.
In-situ surfactant-free emulsion polymerization was utilized to prepare polyacrylate/polyurethane (PUA) microemulsions in the absence of surfactant and organic solvent. For this purpose, PUA with higher acrylate content was successfully prepared, with the aim to reduce the coating cost. The dynamic light scattering results showed that the particle size of PUA microemulsion displayed a unimodal distribution and the particle size was ranged from 33 to 61 nm. In comparison with PUA prepared with conventional miniemulsion polymerization, the particle size distribution coefficient dropped by one order. Atomic force microscopy, together with thermogravimetric analyzer, demonstrated good compatibility and interaction between PU and acrylic components, and no phase separation was detected even at 58 wt% acrylic content. With the incorporation of acrylic component, the thermal stability and maximum stress were improved. The maximum stress greatly increased from 4.6 to 30.9 MPa, and the maximum stress of in-situ PUA was nearly three times larger than that of PUA prepared by miniemulsion polymerization. The effects of acrylic content on water resistance, pencil hardness, adhesion, and impact strength of wood coating were evaluated. With increasing the acrylic content, the water resistance and pencil hardness increased, though the impact strength of in-situ PUA films was slightly reduced.
In this paper, waterborne ultraviolet (UV)-curing wood coatings were modified by nano MgCO3 puree, and prepared by optimizing the process parameters. The mechanical properties (hardness, adhesion and resistance impact strength) and gloss of waterborne UV-curing wood coatings modified by nano MgCO3 puree were tested. It was found that the mechanical properties of coatings increased when nano MgCO3 content increased from 0 to 3.0%. Waterborne UV-curing wood coatings had good hardness, adhesion and impact strength when the nano MgCO3 content was 3%-4%. The hardness was 3H, the adhesion was grade 1, and impact strength was 40 kg∙cm. However, when nano MgCO3 content was higher than 4%, the mechanical properties of coatings decreased. As the nano MgCO3 content gradually increasing, the gloss of waterborne UV-curing wood coatings modified by nano MgCO3 puree decreased. When the nano MgCO3 content was 4.0%, the gloss of coating was 33%. When the nano MgCO3 content exceeded 4.0%, the gloss of waterborne UV-curing wood coatings displayed matte.
The photopolymerization of pigmented coatings is a great challenge and hardly investigated in the literature. Therefore, in this work, the effect of photopolymerization temperature and light intensity on the curing behavior of a TiO 2 -pigmented UV curable epoxy acrylate system was investigated by using photo-differential scanning calorim-etry (photo-DSC) analysis. The rate of conversion and ulti-mate conversion at four different temperatures (i.e., 25, 45, 65, and 85 °C) and four light intensities (i.e. 2, 20, 40 and 80 mW cm -2) for unpigmented and pigmented formula-tions were measured. The effect of photo-polymerization temperature and light intensity on the kinetics constants was also evaluated. It was observed that the rate of conversion and final conversion values were affected by the temperature and UV-light intensity. It was seen that the rate of conver-sion and ultimate conversion had their maximum values at 65 °C for unpigmented formulations. However, in pig-mented formulations, these two parameters improved by increasing the temperature even up to 85 °C. Increasing the temperature caused an increase in the amount of propagation and termination rate constants in both pigmented and un-pigmented formulations although the changes in the pig-mented formulation were more pronounced. It was observed that the rate of polymerization and ultimate conversion for unpigmented formulations increased by increasing the light intensity up to 20 mW cm -2 and then decreased. On the other hand, it was found that these two parameters increased by increasing light intensity up to 40 mW cm -2 when pig-mented formulations used. Finally, the dependence of ter-mination and propagation kinetics constants on light intensity was established for both unpigmented and pig-mented coatings.
This review addresses trends in the development of high performance polyurethane (PU) and its subclass coatings. Changes in the understanding the technical requirements and properties, along with novel approaches in creating high performance PU films are discussed. Some discussion of developments leading to the current status is provided, along with opportunities for the development of architectural, domestic and automotive coatings from carbamate chemistry. The review also focuses on the chemistry of PU, the importance of side products such as biuret, allophanate formation, as well as different low VOC PU coatings such as moisture-cured PU-urea, polyurea, PU-imide, UV cure and waterborne PU coatings. A brief description of functionalized dendritic/hyperbranched polymers, different monomers and synthetic approaches, and their use in the PU coating sector is addressed. In the context of nanostructuring, sol–gel chemistry to formulate ceramer coatings and use of functionalized nanomaterials in PU coatings is described. This portion also includes silica grafting and functionalization of nanosilica particles, polyhedral oligomeric silsesquioxane and the use of bridged polysilsesquioxanes in PU coatings. A wide variety of fillers, whiskers and fibers as well as clay and wollastonites with structural modification is described for use in nanocomposite PU coatings, with special emphasis on the latest development in PU-layered silicate nanocomposites.The use of different reactive-type organophosphorus compounds, aziridinyl curing agents in aqueous PU dispersions, phosphazenes, organo-boranes such as different carboranes for use in the formulation of flame retardant coatings is described. Since surface properties determine the resistivity of coatings towards corrosive chemicals, moisture and dirt repellency, a portion of the review will also be devoted towards modification of surface properties using fluoropolymer, and the synthesis and a brief description of the available fluorinated diols is given.
Recovery of heat energy from internal combustion engine exhaust will achieve significant road transportation CO2 reduction. Turbocharging and turbogenerating are most commonly used technologies to recover engine exhaust heat energy. Engine
exhaust pulse flow can significantly affect the turbine performance of turbocharging and turbogenerating systems, and it is
necessary to consider the pulse flow effects in turbine design and performance analysis. An investigation was carried out
by numerical simulation on the mixed flow turbine pulse flow performance and flow fields. Results showed that the variations
of the turbine efficiency and flowfiled under pulsating flow conditions demonstrate significant unsteady effects. The effect
of blade leading edge sweep on turbine pulse flow performance was studied. It is shown that increasing of the leading edge
sweep angle can improve the turbine average instantaneous efficiency by about 2 percent under pulsating flow conditions.
Keywordswaste heat recovery–mixed flow turbine–pusle flow
Free Access link "http://www.tandfonline.com/eprint/K479q3ERsRXnkMCpjApw/full"
A series of Novel waterborne UV-Curable polyurethane dispersions were synthesized from castor oil, IPDI, DMPA and HEMA by acetone process. The prepared UV-PUD was mixed with three different monomers are characterized for the parameters relevant to the study by physical, spectroscopic, and chemical methods. The effect of monomer type, on the physico-chemical and thermal properties of UV-PUDs revealed that the number of unsaturated groups present in the monomer had a pronounced effect on physico-chemical, mechanical and thermal properties. The combination of renewable resource and environment compliant technology make these UV-PUDs to find potential scope in coating applications.
The photopolymerization of pigmented coatings
is a great challenge and hardly investigated in the literature.
Therefore, in this work, the effect of photopolymerization
temperature and light intensity on the curing behavior of a
TiO2-pigmented UV curable epoxy acrylate system was
investigated by using photo-differential scanning calorimetry
(photo-DSC) analysis. The rate of conversion and ultimate
conversion at four different temperatures (i.e., 25, 45,
65, and 85 �C) and four light intensities (i.e. 2, 20, 40 and
80 mW cm-2) for unpigmented and pigmented formulations
were measured. The effect of photo-polymerization
temperature and light intensity on the kinetics constants was
also evaluated. It was observed that the rate of conversion
and final conversion values were affected by the temperature
and UV-light intensity. It was seen that the rate of conversion
and ultimate conversion had their maximum values at
65 �C for unpigmented formulations. However, in pigmented
formulations, these two parameters improved by
increasing the temperature even up to 85 �C. Increasing the
temperature caused an increase in the amount of propagation
and termination rate constants in both pigmented and unpigmented
formulations although the changes in the pigmented
formulation were more pronounced. It was observed
that the rate of polymerization and ultimate conversion for
unpigmented formulations increased by increasing the light
intensity up to 20 mW cm-2 and then decreased. On the
other hand, it was found that these two parameters increased
by increasing light intensity up to 40 mW cm-2 when pigmented
formulations used. Finally, the dependence of termination
and propagation kinetics constants on light
intensity was established for both unpigmented and pigmented
coatings.
A major change in coatings technology was caused by the restrictions on volatile organic compounds (VOC) in coatings. These government regulations combined with performance advantages were the key to the success of waterborne polyurethanes. The production and chemistry of waterborne one-component polyurethanes and reactive two-component systems are discussed. Examples for their application, predominantly in the field of surface coatings, are given.
The waterborne polyurethane-acrylate (PUA) oligomer was firstly prepared based on isophorone diisocyanate (IPDI), polyether polyol (NJ-210), dimethylol propionic acid (DMPA) and hydroxyethyl methyl acrylate (HEMA) via in situ and anionic self-emulsifying method. The UV-curable polyurethane-acrylate (UV-PUA) was obtained with oligomer, monomers (BA and TPGDA) and photoinitiator Darocur 1173. FT-IR, DSC and TGA were employed to investigate the structures and thermal properties of the UV-PUA films. The effects of BA/TPGDA (R) value, the content of Darocur 1173 and the UV curing time on the performances were investigated. Some mechanical performances, solvent resistance and the gel content of UV-PUA films were measured. When the ratio of BA/TPGDA was 5/5, the UV-PUA film had the best solvent (water, alkali and ethanol) resistances. Besides, with the ratio of the BA/TPGDA increasing, the surface drying time increased. When the content of Darocur 1173 was 4%, the gel content achieved the maximum while the surface drying time achieved the minimum. The obtained UV-curable polyurethane-acrylates are promising as oligomers for UV-curable coatings, plastics, inks and adhesives.
A series of UV curable highly branched waterborne polyurethane acrylates (BWPUAs) were synthesized using an “oligomeric A2+B3” approach. The thiol-endcapped difunctional oligomeric A2 was synthesized first by the addition reaction of isophorone diisocyanate, α,α-dimethylol propionic acid and 2-hydroxyethyl acrylate, then further underwent thiol-Michael reaction with 1,6-hexamethylene bis(thioglycolic acetate). Trimethylolpropane triacrylate was used as a B3 monomer. The molecular structures were characterized with FT-IR and 1H NMR spectroscopy. 1,6-Hexanediol diacrylate (HDDA) was incorporated into the polymeric chain for preparing the HDDA-modified BWPUAs (BWPUA-Hs). For the comparison, the linear waterborne polyurethane acrylate (LWPUA) was synthesized. The UV curing kinetics study results by using the photo-DSC approach showed that the BWPUAs possessed higher photopolymerization rate and final unsaturation conversion in the UV cured films compared with the LWPUA, which increased with the increase of unsaturation concentration in BWPUA. Moreover, the photopolymerization performance, and water and solvent resistance properties were greatly enhanced by the incorporation of HDDA segment into the BWPUA chain. The dynamic mechanical thermal analysis results showed that the elastic modulus in the rubbery plateau, and the glass transition temperature of UV cured film increased with increasing unsaturation concentration in BWPUA, whereas decreased with the introduction of HDDA flexible segment. The thermogravimetric analysis confirmed the high thermal stability of UV cured BWPUA films. All UV cured BWPUA and BWPUA-H films showed better flexibility and middle refractive indices due to the thioether linkage in the polymer network.
Three waterborne polyurethane dispersions derived from polycarbonate of hexanediol (PCD) with molecular weight of 1000Da were synthesized by the acetone method and used as coatings for stainless steel plates. Different hard segments content in the polyurethanes were obtained by varying the isocyanate/macroglycol (NCO/OH) molar ratio. A decrease in the NCO/OH ratio produced an increase in the mean particle size as well as a decrease in the Brookfield viscosity of the dispersions. Furthermore, the greater the NCO/OH ratio the higher the urea and urethane hard segment content, the higher the glass transition temperature value and the higher the elastic modulus of the polyurethane was. On the other hand, the NCO/OH ratio affected the adhesion of the polyurethanes. The adhesion was evaluated by using three different procedures: T-peel strength tests of flexible PVC/waterborne polyurethane dispersion/flexible PVC joints; single lap-shear tests of aluminium/waterborne polyurethane dispersion/aluminium joints and cross-cutter adhesion test of polyurethane coatings on stainless steel pieces. Finally, several properties of the polyurethane coatings on stainless steel pieces were tested including Persoz hardness, gloss, chemical resistance and yellowness index.
Waterborne UV-curable polyurethane dispersions were synthesized from C5/C6 copolymers of polycarbonate diol(PCDL)s and different end-capping groups. The effects of the polyol molecular weight on the UV-curing behavior and physical properties were examined according to the molecular weight (800, 1000, 2000g/mol) of PCDL. The UV-curing behavior was analyzed by Fourier transform infrared spectroscopy and photo-differential scanning calorimetry. The influence of the functionality of the end-capping group on the UV-curing behavior and physical properties were also investigated in a similar manner. 2-Hydroxyethylmethacrylate, 2-hydroxyethylacrylate and pentaerythritol tri-acrylate were used to impart mono-methacrylate, mono-acrylate and tri-acrylate functionality to the end-capping group, respectively. The pendulum hardness, curing rate and conversion increased with decreasing molecular weight of the PCDL. The pendulum hardness, curing rate and conversion of dispersion with tri-acrylate functionality on end-capping groups were much higher than those of the other dispersions with mono-methacrylate or mono-acrylate functionality.
Waterborne polyurethane adhesives are an interesting alternative to the current solvent-borne polyurethane adhesives used in the industry. Different aliphatic waterborne polyurethane dispersions (PUDs) with different solids content were synthesised by reacting isophorone diisocyanate (IPDI) with a polycarbonate derived from hexanediol via the acetone method. The PUDs were characterised by Brookfield viscosity, pH, particle size, transmission electron microscopy (TEM) and solids content measurement. The dry polyurethane films were characterised by ATR-IR spectroscopy, plate–plate rheology, differential scanning calorimetry (DSC) and thermal gravimetry (TGA). Their adhesion was evaluated from T-peel tests of flexible PVC/waterborne polyurethane dispersion/flexible PVC joints and single lap-shear tests of aluminium/waterborne polyurethane dispersion/aluminium joints.The PUDs showed bimodal particle size distribution. The mean particle size of the PUDs decreased by increasing their solids content but the particle size distribution of the PUDs increased by decreasing their solids content. As the solids content increased the Brookfield viscosity of the PUDs increased due to lower mean particle size where particle crowding was favoured, the PUD having 44wt% solids content was an exception (higher particle size but lower polydispersity). On the other hand, the increase in the solids content increased the hard segments content and the degree of phase separation of the polyurethanes. The greater the solids content of the polyurethanes, the lower their glass transition temperatures values and the lower the elastic moduli. Adhesive strength under peel stresses were not affected by the solids content in the polyurethanes but the single lap-shear strength values decreased by increasing the solid contents in the polyurethanes due to lower hard segments content.
Water-dispersible glycidyl carbamate (GC) functional resins were synthesized and crosslinked using a water-dispersible amine
to form coatings. GC functional resins are synthesized by the reaction of an isocyanate functional compound with glycidol
to yield a carbamate (urethane) linkage (–NHCO–) and reactive epoxy group. The combination of both functionalities in a single
resin structure imparts excellent mechanical and chemical properties to the coatings. Previous studies on the development
of GC coatings have focused on solvent-borne coating systems. In this study, GC resins were modified by incorporating nonionic
hydrophilic groups to produce water-dispersible resins. To determine the influence of the content of hydrophilic groups on
dispersion stability, aqueous dispersions were made from a series of hydrophilically modified GC resins and characterized
for particle size and dispersion stability. The composition of a typical, dispersed GC resin particle was predicted using
Monte Carlo simulations. Stable GC dispersions were used to prepare amine-cured coatings. The coatings were characterized
for solvent resistance, water resistance, hardness, flexibility, adhesion, and surface morphology. It was observed that GC
resins were able to be dispersed in water without using any surfactant and by minimal mixing force (hand mixing) and produced
coating films with good properties when crosslinked with a compatible waterborne amine crosslinker.
A new ultraviolet (UV) curable waterborne polyurethane was prepared by modifying the conventional method of anionic aqueous polyurethane. Acrylate groups were introduced into the side chains and the end of the polyurethane main chains using the dihydric acrylate named as PEDA and the single-hydroxyl acrylate named as HEA. The CC content in the chain of the polyurethane was raised effectively and the maximum CC content achieved by this method is 4.5meq/g. The structure was confirmed by the Fourier transform infrared spectroscopy (FTIR). The effects of different CC content were studied by evaluating various properties of the film such as the MEK resistance, hardness, thermal stability and the tensile properties. The curing rule of the polyurethane for different CC content had been investigated during the curing process.
a b s t r a c t Room temperature self-curable silanized waterborne polyurethanes (Si-WPU) were synthesized by means of the acetone process employing covalently linked (3-aminopropyl)triethoxysilane (APTES) as curing agent. The insertion of this curing agent was confirmed using FTIR spectroscopy, liquid NMR and elemental analysis. The APTES concentration induced an increase of particle size, this effect being more pronounced at higher concentrations due to the condensation of the alkoxysilane groups. The conden-sation of silanol groups was evidenced by means of TEM, FTIR and SEM measurements. The presence of silanol groups on the particle surface was demonstrated by 2-potential analyses. Finally, the curing process of the dispersions was followed by means of gel content measurements, solid-state 29 Si-NMR and FTIR studies. All the samples were able to cure at room temperature, and the extent of curing was dependent on the APTES concentration and curing temperature.
The development of photopolymers was helped by the development of photocalorimetry, which is now a basic technique for the study of these materials. This work shows how to obtain vitrification times in single isothermal curing experiments by monitoring the reversing heat capacity along time in modulated temperature DSC-photocuring systems, overcoming the time-consuming problem of standard DSC. The effects of the light intensity and the isothermal curing temperature on the vitrification time of a photocurable system were evaluated. The results obtained at a given curing temperature with different light intensities indicate that the UV-light affects the molecular mobility hindering the vitrification process. The effects of the curing temperature on the vitrification time, the conversion at the vitrification time and the maximum conversion were also evaluated.
Anionomer-type waterborne polyurethanes (PUs) were obtained from poly(β-methyl-δ-valerolactone) glycol (PMVL) and isophorone diisocyanate, following a prepolymer mixing process. The soft-hard segment phase separation in response to the variations of composition and structure of PU has been studied from the dynamic mechanical measurements of the emulsion cast films. The structural variation included ionic and hard segment content, molecular weight of NCO-terminated prepolymer, and type and length of the soft segment. It was found that phase separation is more sensitive to the soft segment length, rather than the soft segment content. With only phase separation, the rubbery modulus was significant even with lower hard segment content. Phase separation was much more pronounced with PU from poly(tetramethylene adipate) glycol, rather than from PMVL and poly(caprolactone) © 1996 John Wiley & Sons, Inc.
Waterborne polyurethane (PU) dispersions were prepared from isophorone diisocyanate (IPDI), 2-bis(hydroxymethyl) propionic acid (DMPA), 1,4-butane diol (BD), poly(propylene glycol) (PPG), and triethylamine (TEA) by means of phase inversion through the acetone process. Changes in DMPA content, initial PU content in acetone, phase-inversion temperature, evaporation conditions, and solvent nature were found to have a great impact on dispersion properties. Using a DMPA concentration of 0.30 mmol/gpol, stable PU dispersions could only be obtained when the initial PU content in acetone was at least 60 wt %, and phase-inversion temperature was lower than 30°C. However, when increasing the PU content to 75 wt %, stable dispersions were obtained using DMPA concentrations three times lower. Finally, viscosity curves during the water addition step as well as a phase diagram were determined to understand the particle formation mechanism. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
A series of waterborne polyurethanes (WBPU) containing different amount of 2,2-bis(hydroxymethyl) propionic acid (DMPA) were synthesized using prepolymer mixing process. Relationships between the DMPA content and physical, mechanical, and thermal properties as well as adhesive behavior at different condition were investigated. Stable aqueous dispersions of WBPU were obtained when the DMPA content was more than 10 mol %. At higher DMPA content, the particle size of the WBPU dispersion was lower but the viscosity of the dispersion was higher. Water swelling and tensile strength of the films increased with increasing of DMPA content. The optimum adhesive strength of WBPU adhesives was found to be depended on the DMPA content, pressing temperature, and pressure on adhesion process. The adhesive strength of WBPU adhesives increased with increasing DMPA content. The optimum pressing temperature decreased with increasing DMPA content. The adhesive strength of WBPU adhesives increased with increasing pressure up to 15 kg f/cm2 and then leveled off. The optimum pressing temperature of WBPU adhesives samples containing 24.02, 22.05, and 17.05 mol % DMPA was about 100, 120, and 140°C, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5684–5691, 2006
A series of ultraviolet (UV) curable waterborne polyurethane-acrylate (WPUA) with different average functionalities were synthesized in new methods. The chemical structures of WPUA were confirmed by Fourier-transform infrared spectroscopy (FT-IR) and the effect of average functionality on properties of WPUA was systemically investigated. It was found that the average functionality had a positive effect on the water resistance and tensile strength of WPUA, to make optimal formation of WPUA molecule chains available, whereas the increasing of average functionality decreased the viscosity and extension of WPUA samples. Besides, through the investigation on the UV curing kinetics, it was found that the average functionality too high or too low was unfavorable for the increase of unsaturation conversion. The morphology and microstructure of WPUA films were also comprehensively discussed with WAXD patterns and fractured surface observed from SEM images.
UV curable films were reinforced with an organically modified montmorillonite (MMT). The organically modified MMTs were prepared by an ion exchange process, in which sodium ions were replaced by alkyl ammonium ions. Cetyltrimethylammonium bromide (CTMA) modified clays gave rise to better intercalated clay morphology. The microstructures were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Physical properties were examined by real time infrared spectroscopy (RTIR), differential scanning calorimetry (DSC), photo-DSC, dynamic mechanical thermal analysis (DMTA). Some tensile properties were also reported. Thermal and mechanical properties were generally improved with nanoclay reinforcements. The effects of nanoclays on the properties of UV curable films are critically evaluated in this paper.
- K L Noble
K.L. Noble, Waterborne polyurethanes, Prog. Org. Coat. 32 (1-4) (1997)
131-136.
Radiation Curing in Polymer Science and Technology
- J P Fouassier
- J F Rabek
J.P. Fouassier, J.F. Rabek, Radiation Curing in Polymer Science and Technology,
Kluwer Academic Publishers Group, Dordrecht, Netherlands, 1993.