Thermodynamic Analysis of the Reaction-Induced Phase Separation of Solutions of Random Copolymers of Methyl methacrylate and N,N-dimethylacrylamide in the Precursors of a Polythiourethane Network

E.R. SOULÉ; B. JAFFRENNOU; F. MÉCHIN; J.P. PASCAULT; J. BORRAJO; R. J. J. WILLIAMS

JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS

JOHN WILEY & SONS INC

Año: 2006 vol. 41 p. 52 - 61

0887-6266

In this work, morphological differences over the thickness of modified vinyl-ester (VE)samples are studied. A thermodynamic analysis based in the Flory-Rehner theory isproposed, in order to evaluate the spinodal decomposition temperature evolution during thereaction. This model takes into account changes in (styrene(St)-co-VE)copolymercomposition and binary interaction parameters with conversion. Then, from the energy andmass balance equations, temperature and conversion profiles over the thickness as afunction of reaction time are calculated. Combining these profiles with the proposedthermodynamic model, spinodal decomposition conversion graphs are constructed. In orderto verify model predictions, a synthesized VE resin was modified with 7.5 wt% ofpoly(butadiene-co-acrylonitrile) vinyl terminated (VTBN) elastomer, and then cured inmolds of 3, 7, 12 and 20 mm thickness at 80 ºC. Fracture surfaces were observed byscanning electron microscopy showing morphological differences over thickness, whichcan be explained from the results obtained from the simulation.