Effect of polymer composition on performance properties of maleate-vinyl ether donor-acceptor UV-curable systems.
Keywords: Crosslinking, cure, polyesters, UV, EB, radiation cure, mechanical properties, physical properties, esters, reaction kinetics
UV-curable polymers continue to find new applications as environmental regulations continue to propel coatings research into finding zero or low VOC alternatives. Nonacrylate UV-curable coating technology is an area of research interest, especially in view of the health concerns associated with acrylate systems. The major categories in nonacrylate technology include cationic polymerization, thiol-ene systems, and free-radical induced alternating copolymerization. Some of the benefits to be derived from alternate technologies are those of comparable cure times as acrylates, low toxicity, and, more importantly, that of design flexibility.
Free-radical induced alternating photocopolymerization takes place when an electron-rich vinyl group is mixed with an electron deficient vinyl group. (1-4) It has been found that polymerization kinetics is affected by factors such as photoinitiator concentration, presence of oxygen, light intensity, and composition of the monomer mixture. (5,6) Studies on systems containing a stoichiometric balance of maleate and vinyl ether functional groups have been previously reported. (7-9) Lapin et al. studied the properties of oligomers with different backbones and reactive diluents with different functionalities. (8) The oligomers were then combined with the reactive diluents, UV-cured, and their film properties were evaluated. In another study, Noren evaluated the properties of coatings based on a maleate-vinyl ether system wherein the molecular weight and equivalent weight of the unsaturated polyester were varied. (7) There are reports in literature on the mechanistic and stereochemical aspects of donor-acceptor chemistry. (10-16) Gaylord et al. have generated a substantial body of work in the area of donor-acceptor complexes and a few are cited herein. (17-20) Several patents have also been issued in this area. (21-25) There are no accounts of detailed structure-property relationships in donor-acceptor systems wherein the unsaturated polyester backbone is varied by using different monomer combinations.
We are particularly interested in using UV-curable polymer systems as laminating layers for use in multilayered flexible electronic devices. The performance requirements for this application are complex and challenging. Following curing, the process comprises steps like metallization, chemical etching, laser ablation, and so on. This translates into a demand for a polymer with a complex mix of properties such as films that cure fast, are hard, flexible, transparent, thermally stable, exhibit good solvent and acid etch resistance, and are dimensionally stable. The objective of this study is to evaluate donor-acceptor technology for this application. A series of polymers were synthesized using a wide range of compositions to potentially yield a range of polymer film properties. This data was then used to assess the technology for flexible electronic device manufacture.
All monomers used for polyester synthesis, except 1,4 CHDA (1,4-cyclohexanedicarboxylic acid) and 2-ethyl hexanol, were purchased from Sigma Aldrich. Diethyl maleate and diethyl fumarate used for the model compound study were also purchased from Sigma Aldrich. The 2-ethyl hexanol was purchased from Alfa Aesar and 1,4 CHDA was obtained from Eastman Chemical Company. Triethyleneglycol divinyl ether (TEGDVE) and diethyleneglycol monovinyl ether (DEGMVE) were provided by BASF. Photoinitiator, 2-hydroxy-2-methyl-l-phenyl-1-propanone (Darocur 1173), was supplied by Ciba. All chemicals were used as received without further purification.
The unsaturated polyesters were formulated to be hydroxyl functional with a molecular weight of approximately 800. Compositions were designed so that the average number of double bonds per polymer chain was greater than 2.5 and the desired acid value was less than 30 mg of KOH per gram of sample. Maleic anhydride was the source of unsaturation in all formulations and the monomers used were varied in order to obtain polyesters with a wide range of backbone structures. Chemical composition of the various polyesters and the symbols used to represent them are noted in Table 1. The amounts of monomer used in each formulation and the theoretical molecular weight of the polymers are listed in Table 2.
The unsaturated polyesters were prepared using standard melt polyesterification techniques. Monomers were weighed into a 250-ml, three-necked flask, equipped with a mechanical stirrer, temperature controller, condenser, and a nitrogen inlet. A nitrogen blanket was maintained in the reaction flask during the course of the reaction in order to preclude side reactions, such as oxidation of double bonds. The reaction mixture was heated in a ramped manner and temperatures were set at 60[degrees]C, 120[degrees]C, and 180[degrees]C. Reaction was continued until the desired acid value was reached. Acid value was determined by titration with alcoholic KOH.
Polyester resins were characterized for viscosity, molecular weight, and glass transition temperature. Viscosity measurements were made at 100[degrees]C using an ICI cone and plate viscometer. Molecular weight was determined using a Waters 2410 gel permeation chromatograph equipped with a refractive index detector. A 1% sample solution in tetrahydrofuran using a flow rate of 1 ml/min was used. Calibration was performed using polystyrene standards. Differential scanning calorimetry (DSC) measurements were conducted using a TA Instruments Q1000 series DSC. The testing method used was a heat-cool-heat cycle. The samples were first equilibrated at -70[degrees]C and then subjected to a heat cycle at the rate of 5[degrees]C/min to 200[degrees]C, followed by cooling to -70[degrees]C at a rate of 10[degrees]C/min and a final heating cycle at a rate of 5[degrees]C/min to 200[degrees]C. The ratio of maleate to fumarate isomers was determined by [.sup.1.H] NMR on a Varian Unity/Inova-400NB (400 MHz).
[FIGURE 1 OMITTED]
Coating formulations were prepared by combining the unsaturated polyester and triethyleneglycol divinyl ether in a ratio of 1:1 of the reactive functional groups, viz. maleate to vinyl ether functionality. The mixture was homogenized using heat. Four percent photoinitiator, based on the combined weight of resin and reactive diluent, was added to the formulation followed by mixing to obtain a homogeneous mixture. The coatings prepared from polyesters 1 to 10 were designated as A to J, respectively (see Table 1). For example, coating A was prepared by combining 5.63 g of the unsaturated polyester, 2.12 g of triethyleneglycol divinyl ether, and 0.464 g of the photoinitiator.
Model formulations were prepared by combining the model ester compound with DEGMVE in a ratio of 1:1 of the reactive functional groups, namely ester to vinyl ether functionality. The mixture was homogenized and 4% of the photoinitiator, based on the combined weight of model ester and reactive diluent, was added to the formulation followed by mixing to obtain a uniform mixture.
Coatings were deposited onto a substrate using a drawdown bar with a 4 mil clearance. Substrates used were aluminum for hardness measurement and glass to obtain free films for DMTA and other tests. Application was followed by curing of samples under ultraviolet (UV) light until films that were nontacky to touch were obtained. A Dymax 200 EC silver lamp (UV-A, 365 nm) with an intensity of 35 mW/[cm.sup.2], measured with an International Light digital radiometer (Model IL1400A), was used as the source for UV radiation. Testing of film samples was performed after allowing the samples to equilibrate at room temperature for at least 24 hr.
Real time FTIR measurements were made using a Nicolet Magna FTIR spectrometer. A LESCO Super Spot MK II UV curing lamp equipped with a fiber optic light guide was the source for UV irradiation of samples. The uncured sample was spin-coated at an rpm of 3000 onto a KBr disk and was simultaneously exposed to IR and UV irradiation. The sample was placed at a distance of 20 mm from the end of the fiber optic cable. Light intensity at the sample was 10 mW/[cm.sup.2]. In all cases, IR data collection was continued after UV irradiation was stopped.
Photo-DSC measurements were obtained using the TA Instruments Q1000 DSC outfitted with a photocalorimetric accessory (PCA). The samples were subjected to UV irradiation for 150 and 300 sec at an intensity of 40 mW/[cm.sup.2] using fiber optic light guides.
[FIGURE 2 OMITTED]
Dynamic mechanical properties of cured films were evaluated using a dynamic mechanical thermal analyzer (DMTA 3E, Rheometric Scientific). Free films 3 mm long, 5 mm wide, and 0.05-0.08 mm thick were characterized using settings at a frequency of 10 rad/sec and heating rate of 5[degrees]C/min over a temperature range of -50[degrees]C to 250[degrees]C. The geometry employed was that of rectangular tension/compression. Thermogravimetric analysis was run using a Perkin Elmer thermogravimetric analyzer and samples were heated from 25[degrees]C to 650[degrees]C, at a rate of 10[degrees]C/min. Film hardness was measured using a BYK-Gardner pendulum hardness tester on aluminum panels and Konig hardness value was reported in seconds.
RESULTS AND DISCUSSION
The unsaturated polyester resins described in Table 2 were synthesized and characterized. The results are outlined in Table 3. The number average and weight average molecular weights obtained using GPC are in reasonable agreement with design values. Polydispersity (PD) of the synthesized polyesters was found to range between 1.40 and 2.15, typical of polymers synthesized by step growth polymerization.
Analysis of glass transition temperatures shows that compositions containing HD yield comparatively lower glass transition temperatures than compositions without it. It is further seen that HD in combination with TEG further lowers the glass transition temperature. Compositions consisting of only flexible monomers HD/DEG/CHDA have the lowest glass transition temperatures.
The viscosity of the polyester resins varies as a function of composition. With a few exceptions, the viscosity trend is similar to the glass transition trend. Compositions that contain HD generally show lower viscosity as compared to those without it. The HD/TEG combinations lowers the viscosity further. The HD/TEG/CHDA combination yields the lowest viscosity. As expected, a combination of HD/CHDM/EH also yields a very low viscosity. The composition TMP/HD/CHDA/MA has a higher viscosity that may be attributed to the fact that this is a branched polymer due to the presence of the trifunctional monomer, TMP. It is also observed that polyesters that contain IPA yield higher viscosity and glass transition temperatures than those containing 1,4-CHDA.
Coating formulations were prepared with the unsaturated polyesters and stoichiometric amounts of triethyleneglycol divinyl ether plus a photoinitiator. The coating formulations were evaluated for cure characteristics, and then the mechanical and thermal properties of the cured films were studied.
REAL TIME INFRARED SPECTROSCOPY: Real-time IR was used to study the disappearance of the vinyl ether peak at 1639 [cm.sup.-1] as well as to monitor the extent of reaction. Since the donor-acceptor polymerizations are stoichiometric, the conversion of vinyl ether groups also indicated the conversion of maleate/fumarate groups. In order to study the effect of composition on the extent of cure, samples were subjected to a 150-sec UV light exposure and typical results obtained are shown in Figure 1. The degree of conversion was calculated using equation (1):
% conversion = ((([A.sub.1639])[.sub.0]-([A.sub.1639])[.sub.t])/([A.sub.1639])[.sub.0])x100 (1)
where ([A.sub.1639])[.sub.0] is the absorbance at time=0 and ([A.sub.1639])[.sub.t] is the absorbance at time t.
It was also observed that the conversions were a function of both the polymer composition and the exposure time. The change in vinyl ether conversion as a function of different UV exposure times is illustrated in Figure 2. In light of this, RTIR experiments were conducted for all samples at several exposure times. Percent conversions were calculated at 30 and 150 sec and compiled in Table 4.
[FIGURE 3 OMITTED]
The data shows that complete conversion was not obtained. This may be attributed to an increase in viscosity as cure proceeds and the subsequent inability of the reacting moieties to find each other due to sluggish segmental mobility. A general trend was observed: when the constituent polyester had a higher [T.sub.g], lower conversions were observed, and vice versa. Another factor that influenced conversion was the viscosity of the coating. Coating H, despite having a low [T.sub.g], showed very low conversion that may have been due to high viscosity of the constituent polyester, which in turn could be attributable to the presence of a tri-functional monomer. Thus, the initial viscosity of the polyester has an impact on the ultimate conversion achieved.
PHOTO DIFFERENTIAL SCANNING CALORIMETRY (PDSC): Heat flow for cure reaction was determined for coatings, including the model compound formulations, using a PDSC. Two different UV exposure times were used: 300 sec and 150 sec. The purpose of the longer exposure was to force complete conversion of double bonds. The shorter exposure was used to obtain conversion data comparable to RTIR. Model compounds were prepared by combining diethyl maleate and diethyl fumarate separately with DEGMVE. The [T.sub.g]s of diethyl maleate and diethyl fumarate cured with DEGMVE were determined using a DSC and were found to be -10.88[degrees]C and -14.8[degrees]C, respectively. Since the [T.sub.g]s of model polymers were below the temperature used for the PDSC experiments (30[degrees]C), we assumed that no vitrification had occurred, thus the heat evolved in the curing of the model compounds represented the maximum achievable.
[FIGURE 4 OMITTED]
[FIGURE 5 OMITTED]
The PDSC results are compiled in Tables 5 and 6 for different UV exposure times. Heat of reaction data was further converted into double bond conversion, using inputs from NMR and PDSC. The calculations that were used to convert data are described as follows.
The heat of reaction (J/g) was calculated by integrating the area under the curve from 0 to 2.5 min (UV exposure=150 sec) from the PDSC and converted to kJ/C=C (total unsaturation). NMR was used to determine % maleate and % fumarate in the constituent polyester samples. Theoretical heat of reaction was calculated using equation (2):
[H.sub.max(theo)] = (M*[H.sub.M]) + (F*[H.sub.F]) (2)
[H.sub.max(theo)] = Maximum theoretical heat of reaction
M = fraction maleate determined by NMR
F = fraction fumarate determined by NMR
[H.sub.M] = Heat of reaction for diethyl maleate/vinyl ether
[H.sub.F] = Heat of reaction for diethyl fumarate/vinyl ether
Percentage of double bond conversion was obtained as per equation (3):
% double bond conversion = [Heat of reaction/[H.sub.max(theo)]] x 100 (3)
Kinetic studies confirmed that as UV exposure time increased, the double bond conversion increased. It was seen that the polyester [T.sub.g] significantly influenced the double bond conversion. A general trend observed was that as the [T.sub.g] increased, the conversion decreased (depicted in Figures 3 and 4).
DYNAMIC MECHANICAL THERMAL ANALYSIS (DMTA): DMTA was used to determine the glass transition temperature and crosslink density of the coatings. The values obtained are shown in Table 7. As expected, the crosslink densities and glass transition temperatures were found to vary as a function of composition.
Backbone structure influences the [T.sub.g] of coatings. The presence of aromatic and/or cyclic monomers resulted in coatings with high [T.sub.g] values. It was seen that coatings that comprised flexible monomers like HD or EH showed relatively low [T.sub.g].
The crosslink density fell into a rather narrow range, with the exception of samples F and J. Since we attempted to maintain the same vinyl (maleic) functionality for all of the polyesters and also since the crosslinking reaction was stoichiometric, this was not unexpected. Samples F and J, which had much lower crosslink density, were made from polyesters 6 and 10. These polydesters had the highest acid values, which suggests that the degree of polymerization was not as high for these two polymers as the others. Thus, lower crosslink density was a result of the lower vinyl functionality.
Thermal stability of the cured coatings was compared for weight loss at a temperature of 150[degrees]C and the values were found to be less than 4%, which may be attributed to moisture loss or a volatilization of low molecular weight, unreacted components in the crosslinked film. A temperature of 150[degrees]C was chosen based on the temperature that the coating would be subjected to during the subsequent manufacturing process. The thermal stability curves are shown in Figure 5.
Coatings with an aromatic backbone showed better thermal stability at a temperature of 600[degrees]C. It was also seen that coatings containing CHDA showed lower thermal stability at a temperature of approximately 200[degrees]C, as in the case of E, and at 600[degrees], in the case of coatings H and F.
[FIGURE 6 OMITTED]
Koing pendulum hardness was determined for the coatings and, as expected, it was found to change with the composition. Figure 6 illustrates the trend observed for hardness values. A general trend observed was that formulations with aromatic backbones like A, B, C, D, E, and I showed generally higher hardness values. The hardness values also appeared to be related to the degree of crosslinking. Coatings F and J had a low crosslink density, resulting in a low pendulum hardness value.
Donor-acceptor radiation-curable coatings can be designed in order to meet specific application requirements. This is achieved by varying the composition of the unsaturated polyester backbone. Polyester properties such as viscosity and glass transition temperatures were found to change as the proportion of flexible monomers used were changed. Further trends in property changes were observed when the coatings prepared from these polyesters were tested. Cure times and conversions were found to vary as a function of both composition and UV exposure times. Kinetic studies using PDSC confirmed the observation from RTIR that [T.sub.g] influenced the double bond conversion. It was seen that lower polyester [T.sub.g] resulted in higher conversion, and vice versa. The study also confirmed the RTIR observation that higher conversion is obtained when the UV exposure time is increased. The glass transition temperature and crosslink densities were found to be different when the composition changed. The coatings prepared exhibited good hardness values and higher hardness values were observed in compositions containing aromatic or aromatic-like monomers. All coatings exhibited good thermal stability.
We would like to thank the Defense Microelectronics Activity (contract #DMEA90-02-C-0224) for funding this project.
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Neena Ravindran, Ankit Vora, and Dean C. Webster ([dagger])--North Dakota State University*
Presented at the e|5 2004, sponsored by RadTech International North America, May 2-5, 2004, in Charlotte, NC.
* Dept. of Coatings and Polymeric Materials, 1735 NDSU Research Park Dr., P.O. Box 5376, Fargo, ND 58105.
([dagger]) Author to whom correspondence should be addressed. Email: email@example.com.
Table 1 -- Polyester Compositions Polyester Monomer Composition (a) Coating 1 NPG/IPA/DEG/MA A 2 CHDM/DEG/AA/IPA/MA B 3 DEG/PG/IPA/MA C 4 HD/TEG/IPA/MA D 5 HD/NPG/TEG/IPA/MA E 6 HD/NPG/TEG/CHDA/MA F 7 DEG/HD/CHDA/MA G 8 TMP/HD/CHDA/MA H 9 DEG/NPG/IPA/MA I 10 HD/EH/CHDA/MA J (a) NPG: neopentyl glycol, IPA: isophthalic acid, DEG: diethylene glycol, MA: maleic anhydride, CHDM: 1,4-cyclohexane dimethanol, AA: adipic acid, PG: propylene glycol, HD: 1,6-hexane diol, TEG: triethylene glycol, CHDA: 1,4-cyclohexane dicarboxylic acid, TMP: trimethylol propane, EH: 2-ethyl hexanol. Table 2 -- Formulations and Theoretical Molecular Weight of Polyester Resins Polyester NPG DEG TEG CHDM 1,6 HD TMP IPA AA 1 0.878 0.627 0.206 2 0.953 0.713 0.198 0.146 3 1.421 0.160 4 0.491 1.015 0.218 5 0.512 0.236 0.767 0.210 6 0.512 0.236 0.768 7 0.824 0.625 8 1.161 0.387 9 0.950 0.570 0.166 10 1.334 Mol. Wt. Polyester 1,4 CHDA EH MA (Theo.) 1 1.00 672 2 1.00 780 3 1.00 776 4 1.00 953 5 1.00 776 6 0.235 1.00 679 7 0.172 1.00 772 8 0.333 1.00 1034 9 1.00 727 10 0.200 0.111 1.00 776 Table 3 -- Properties of the Unsaturated Polyesters Viscosity (Poise) Polyester Acid Value at 100[degrees]C [bar.M.sub.n] 1 21 5.4 1352 2 17 7.1 1157 3 15 4.2 1193 4 6 4.6 1803 5 13 5.0 2341 6 29 2.2 1337 7 14 3.4 1492 8 16 9.5 1829 9 2 5.8 1256 10 30 2.4 1394 Polyester [bar.M.sub.w] PD [T.sub.g][degrees]C 1 1888 1.40 -12.47 2 1927 1.67 -15.50 3 2112 1.77 -18.73 4 3254 1.80 -35.61 5 3193 1.36 -28.04 6 1965 1.47 -31.97 7 2489 1.67 -41.07 8 3933 2.15 -36.62 9 2323 1.85 -9.57 10 2263 1.62 -39.36 Table 4 -- Conversion of Vinyl Ether Groups at 1639 [cm.sup.-1] After UV Exposure Times of 30 and 60 sec Coating A B C D E % Conversion after 30 sec 39 55 59 65 61 % Conversion after 150 sec 61 69 73 77 75 Polyester [T.sub.g] ([degrees]C) -12.47 -15.5 -18.73 -35.61 -28.04 Coating F G H I J % Conversion after 30 sec 60 50 53 45 63 % Conversion after 150 sec 84 63 57 62 84 Polyester [T.sub.g] ([degrees]C) -31.97 -41.07 -36.62 -9.57 -39.36 Table 5 -- Heat of Reaction Using PDSC and Double Bond Conversion After UV Exposure=150 sec No. of Heat of Maleic Reaction Units/ % Maleate % Fumarate (J/g): UV Polymer from from Irradiation Composition Notation Chain NMR NMR = 150 sec Model 1 DM 100 529.40 Model 2 DF 100 483.70 NPG/IPA/DEG/ A 2.51 59.18 40.82 275.85 MA CHDM/DEG/AA/ B 2.38 70.67 29.33 273.70 IPA/MA DEG/PG/IPA/ C 3.06 61.69 38.31 320.97 MA HD/TEG/IPA/ D 2.15 69.60 30.40 311.20 MA HD/NPG/TEG/ E 2.69 70.59 29.41 302.47 IPA/MA HD/NPG/TEG/ F 2.30 70.15 29.85 280.57 CHDA/MA DEG/HD/CHDA/ G 2.72 81.34 18.66 336.87 MA TMP/HD/CHDA/ H 3.28 53.05 46.95 291.53 MA DEG/NPG/IPA/ I 2.77 67.95 32.05 288.27 MA HD/CHDM/EH/ J 2.39 65.64 34.36 269.50 MA Heat % Double Moles of Reaction [H.sub.max(theo)] Bonds Composition Notation C=C (kJ/C=C) (kJ/C=C) Converted Model 1 DM 0.0302 175 Model 2 DF 0.0300 161 NPG/IPA/DEG/ A 0.0294 94 170 55 MA CHDM/DEG/AA/ B 0.0256 107 171 62 IPA/MA DEG/PG/IPA/ C 0.0291 110 170 65 MA HD/TEG/IPA/ D 0.0288 108 171 63 MA HD/NPG/TEG/ E 0.0281 108 171 63 IPA/MA HD/NPG/TEG/ F 0.0287 98 171 57 CHDA/MA DEG/HD/CHDA/ G 0.0273 123 173 71 MA TMP/HD/CHDA/ H 0.0234 125 169 74 MA DEG/NPG/IPA/ I 0.0306 94 171 55 MA HD/CHDM/EH/ J 0.0249 108 171 63 MA Table 6 -- Heat of Reaction Using PDSC and Double Bond Conversion After UV Exposure=300 sec No. of Heat of Maleic Reaction Units/ % Maleate % Fumarate (J/g): UV Polymer from from Irradiation Composition Notation Chain NMR NMR = 300 sec Model 1 DM 100 553.20 Model 2 DF 100 444.60 NPG/IPA/DEG/ A 2.51 59.18 40.82 289.70 MA CHDM/DEG/AA/ B 2.38 70.67 29.33 270.33 IPA/MA DEG/PG/IPA/ C 3.06 61.69 38.31 357.63 MA HD/TEG/IPA/ D 2.15 69.60 30.40 414.50 MA HD/NPG/TEG/ E 2.69 70.59 29.41 317.30 IPA/MA HD/NPG/TEG/ F 2.30 70.15 29.85 314.00 CHDA/MA DEG/HD/CHDA/ G 2.72 81.34 18.66 347.53 MA TMP/HD/CHDA/ H 3.28 53.05 46.95 287.70 MA DEG/NPG/IPA/ I 2.77 67.95 32.05 320.47 MA HD/CHDM/EH/ J 2.39 65.64 34.36 335.03 MA Heat % Double Moles of Reaction [H.sub.max(theo)] Bonds Composition Notation C=C (kJ/C=C) (kJ/C=C) Converted Model 1 DM 0.0302 183 Model 2 DF 0.0300 148 NPG/IPA/DEG/ A 0.0294 99 169 58 MA CHDM/DEG/AA/ B 0.0256 106 173 61 IPA/MA DEG/PG/IPA/ C 0.0291 123 170 72 MA HD/TEG/IPA/ D 0.0288 144 173 83 MA HD/NPG/TEG/ E 0.0281 113 173 65 IPA/MA HD/NPG/TEG/ F 0.0287 109 173 63 CHDA/MA DEG/HD/CHDA/ G 0.0273 127 177 72 MA TMP/HD/CHDA/ H 0.0234 123 167 74 MA DEG/NPG/IPA/ I 0.0306 105 172 61 MA HD/CHDM/EH/ J 0.0249 135 171 79 MA Table 7 -- Glass Transition Temperature and Crosslink Density of Coatings Coating [T.sub.g] ([degrees]C) Crosslink Density (mol/[cm.sup.3]) A 114.96 5.27 x [10.sup.-3] B 94.929 3.66 x [10.sup.-3] C 104.93 7.07 x [10.sup.-3] D 80.478 3.65 x [10.sup.-3] E 90.08 4.96 x [10.sup.-3] F 90.417 0.13 x [10.sup.-3] G 99.983 5.44 x [10.sup.-3] H 105.43 5.54 x [10.sup.-3] I 139.78 2.53 x [10.sup.-3] J 114.91 0.14 x [10.sup.-3]
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|Title Annotation:||glass transition temperatures|
|Comment:||Effect of polymer composition on performance properties of maleate-vinyl ether donor-acceptor UV-curable systems.(glass transition temperatures )|
|Author:||Webster, Dean C.|
|Article Type:||Case study|
|Date:||Jul 1, 2006|
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