Micro-heterogeneity of urethane vinylester resin networks

Zhang, J; Richardson, Melvin O. W.

doi:10.1016/s0032-3861(00)00040-9

Cited by 14 publications

(8 citation statements)

References 11 publications

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“…It is well known that the glass‐transition temperature is proportional to the crosslink density. Thus, it is reasonable to assign the higher temperature peak to the microgel phase with a higher glass‐transition temperature and the lower temperature peak to the nonmicrogel phase with a lower glass‐transition temperature 17…”

Section: Resultsmentioning

confidence: 99%

“…Thus, it is reasonable to assign the higher temperature peak to the microgel phase with a higher glass-transition temperature and the lower temperature peak to the nonmicrogel phase with a lower glass-transition temperature. 17 Figures 6-8 also shows that the areas for the first peaks (lower temperature peaks) obviously decreased with increasing isothermal temperatures until the first peaks disappeared. However, for the second peaks (higher temperature peaks), the areas were almost unchanged, especially in Figures 7 and 8.…”

Section: Residual Heat Of Isothermal Curing Dsc and Network Microstrumentioning

confidence: 85%

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Effects of initiators on the cure kinetics and mechanical properties of vinyl ester resins

Yang

2008

J of Applied Polymer Sci

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Initiators play an important role in the curing of vinyl ester resins. In this study, two kinds of initiators were used to investigate the effects of initiator systems on the cure kinetics, microstructure, and mechanical properties of vinyl ester resins. The reaction kinetics, investigated with isothermal differential scanning calorimetry (DSC), showed that the combination of different kinds of initiators could significantly decrease the induction times and exothermal peak times and increase the amount of isothermal reaction heat in comparison with a single-initiator system. The residual heat of the isothermal cure of vinyl ester resins, obtained by DSC, demonstrated the existence of microheterogeneity in the cured resins. The DSC data also showed that the highly crosslinked phase (the microgel phase) was more perfect for the resins cured with an initiator-combination system. No significant difference was observed in the mechanical properties of resins cured under different conditions, whereas the cure temperature had a great effect on the mechanical properties of cured resins.

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Section: Resultsmentioning

confidence: 99%

Section: Residual Heat Of Isothermal Curing Dsc and Network Microstrumentioning

confidence: 85%

Effects of initiators on the cure kinetics and mechanical properties of vinyl ester resins

Yang

2008

J of Applied Polymer Sci

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“…After being reheated above T g , the unreacted monomers will react. It is well known that T g is proportional to the crosslinking density 18. Therefore, with reheating, the styrene‐rich phase first reaches its T g , and the monomers trapped in the styrene‐rich phase react first.…”

Section: Resultsmentioning

confidence: 99%

“…However, the VE‐rich phase reaches its T g after the styrene phase, and this results in the monomers trapped in the VE phase reacting second. It is reasonable to assign the first exothermic peaks to the polystyrene‐rich phase with a lower T g and the second exothermic peaks to the VE‐rich phase with a high T g 18…”

Section: Resultsmentioning

confidence: 99%

Cure kinetics, microheterogeneity, and mechanical properties of the high‐temperature cure of vinyl ester resins

Yang

et al. 2004

J of Applied Polymer Sci

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A kinetic model has been developed that is based on the irreversible thermodynamic fluctuation theory, in which the conversion of comonomers is a function of the curing relaxation time, reaction time, and reaction temperature. This modified model permits a better prediction of the course of the high-temperature cure reaction of vinyl ester (VE) resins under isothermal conditions. The microheterogeneity in cured resins was investigated through the measurement of the residual heat of isothermally cured samples with differential scanning calorimetry and through the observation of the fracture surfaces of samples under different cure conditions with scanning electron microscopy (SEM). The SEM photographs demonstrated the existence of clusters of microgels of about 20 m in samples isothermally cured at 80°C for 3 h. The results of the dynamic mechanical thermal analysis of postcured samples verified the microheterogeneity in the cured samples and showed that the glasstransition temperatures were not affected by the curing conditions. The effect of postcuring on the conversions of VE and styrene varied with the different cure schedules. The postcure for a sample isothermally cured at 80°C increased the tensile strength and flexural strength. On the contrary, the postcure for samples isothermally cured at 120°C reduced the tensile strength and flexural strength.

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“…Unsaturated polyurethanes (uPUR), containing double bonds from polyesters soft segments [1][2][3], chain extenders [4,5] or pendant groups [6][7][8][9][10][11][12], belong to a new class of elastomers. Their importance in macromolecular chemistry follows from their possible applicability in syntheses of cross-linked polymers.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Chemical Structure and Properties of Crosslinked Poly(esterurethanes) Based on Unsaturated Oligo(alkyleneester)diols

2007

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Abstract:The cross-linked poly(esterurethanes) (PEU) based on unsaturated oligo(alkyleneester)diol (OAE) are presented. OAE was prepared from adipic acid, maleic anhydride and ethylene glycol and then characterized by elemental analysis, FTIR, 1 H NMR and 13 C NMR spectroscopy in account of double bonds and -COOH end groups. The synthesis of PEU was conducted in two steps. In the first step the prepolymers, containing free NCO or OH groups, were obtained via the reaction of OAE with 4,4`-diphenylmethane diisocyanate (MDI) used in excess. The cross-linking was achieved in the next step, in which the prepolymers were dissolved in methyl methacrylate (MMA) of concentrations in the range of 30 to 50 wt% in the presence of 1 wt% of methyl ethyl peroxide and 0.003 wt% of cobalt (II) 2-ethylhexanoate. It is proved that both chemical structure and MDI content in prepolymer influence the static and dynamic mechanical properties and thermal stability of the poly(esterurethanes).

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Micro-heterogeneity of urethane vinylester resin networks

Cited by 14 publications

References 11 publications

Effects of initiators on the cure kinetics and mechanical properties of vinyl ester resins

Effects of initiators on the cure kinetics and mechanical properties of vinyl ester resins

Cure kinetics, microheterogeneity, and mechanical properties of the high‐temperature cure of vinyl ester resins

Synthesis, Chemical Structure and Properties of Crosslinked Poly(esterurethanes) Based on Unsaturated Oligo(alkyleneester)diols

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