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Analysis of the curing behavior of unsaturated polyester resins using the approach of free radical polymerization
Author(s) -
Han Chang Dae,
Lee DaiSoo
Publication year - 1987
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1987.070330820
Subject(s) - curing (chemistry) , isothermal process , reaction rate constant , materials science , thermodynamics , polymerization , polyester , differential scanning calorimetry , kinetic energy , polymer chemistry , radical polymerization , infrared spectroscopy , degree of polymerization , kinetics , chemistry , composite material , organic chemistry , polymer , physics , quantum mechanics
The approach of free radical polymerization is adapted to develop a kinetic model for predicting the curing behavior of unsaturated polyester resins. The approach taken here is essentially similar to that advanced by Stevenson with some modifications, namely (1) the efficiency of the initiator is assumed to decrease with conversion, (2) no assumption was made a priori on the magnitude of the rate constants for the termination and inhibition reactions, and (3) the propagation rate constant was assumed to be represented by k p = A o exp(− E p / RT ) ˙[1 − (α/α f )] m , and the termination rate constant by k t = B o exp( − E t / RT )[1 ‐ (α/α f )] n , in which A o and B o are preexponential constants, E p and E t are the activation energies for the propagation and termination reactions, respectively, R is the universal gas constant, T is the absolute temperature, α is the degree of conversion, α f is the final degree of conversion, and m and n are constants to be determined by numerical simulation. A computer program was developed to search for the optimal values of all the parameters involved, to minimize the difference between the predicted and experimentally determined rate of conversion and the degree of conversion simultaneously. An experimental study was also conducted on the cure of unsaturated polyester resin, using differential scanning calorimetry (DSC) under isothermal conditions and infrared (IR) spectroscopy. The degree of cure was determined from the total heat generated during cure, with the aid of the IR spectra of the residual double bonds in the cured resin. The predictability of the mechanistic model developed is presented and the usefulness of the model for simulating various processing operations is discussed.