The effects of temperatures, styrene concentration, and molecular composition of unsaturated polyester (UP) prepolymers on the viscosity of UP-styrene systems are studied. The viscosity of U P resins follows the Arrhenius-type expression with resin temperature as well as with the styrene molar fraction of the resin. The two Arrhenius correlations can be combined into a simple dual-Arrhenius equation by combination rule. This dual-Arrhenius equation comprises pseudo viscosity parameters of styrene monomer and U P prepolymer, respectively. The pseudo viscosity parameters of styrene monomer are experimentally found constant; while those of U P prepolymer seem to be number-average molecular weight correlated rather than weight-average molecular weight correlated. The U P prepolymers having different molecular structures show different pseudo viscosity parameters due to their own molecular interaction parameters. The pseudo viscosity parameters of U P prepolymers should be determined experimentally for the time being. 0 1996 John Wiley & Sons, Inc. 'fS, max RT (wt 76) 60 72 62 90 58 60 63 a MA: maleic anhydride, PG: propylene glycol, IPA: iso-phthalic acid, DEG: di-ethylene glycol, NPG; neo-propylene glycol. '/$, max R E maximum styrene weight fraction in UP resin to maintain homogeneous mixture a t room temperature. 0, = MJM.. * Values obtained by eqs. (l), (2), (3), and (lo), i.e., data fitted by correlation order of temperature and, then, styrene mole fraction. Values obtained by eqs. (6), (7), (8), and (lo), i.e., data fitted by correlation order of styrene mole fraction and, then, temperature.
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