Curing of Epoxy–Urethane Copolymers in a Heated Mold: Effect of the Curing Conditions on the Phase-Separation Process

P.M. STEFANI; S.M. MOSCHIAR; M.I. ARANGUREN; C. MARIETA; I. MONDRAGON

JOURNAL OF APPLIED POLYMER SCIENCE

wiley

Año: 2001 vol. 81 p. 889 - 900

0021-8995

The curing process of an epoxy–urethane copolymer in a heated mold wasstudied. The epoxy resin (DGEBA, Araldyt GY9527; Ciba Geigy), was coreacted with aurethane prepolymer (PU, Desmocap 12; Bayer) through an amine that acted ascrosslinking agent (mixture of cycloaliphatic amines; Distraltec). The study focused onthe effect of the curing condition and PU concentration on time–temperature profilesmeasured in the mold and the consequent final morphologies obtained. As the PUconcentration increases, the maximumtemperature reached in the mold decreases as aresult of the dilution effect of the elastomer on reaction heat, whereas the Tg of the piecealso decreases. Phase separation is a function of conversion and temperature reached inthe curing part and was analyzed using experimental data and a mathematical modelthat predicts temperature and conversion throughout the thickness of the mold. Scanningelectron microscopy and atomic force microscopy were used to determine thecharacteristics of the dispersed phase for the different formulations and conditions ofcuring. It was shown that the size of the dispersed phase increased with the initial PUconcentration, whereas there were practically no differences in the separated phase asa function of position or temperature of curing (in the range of 70 to 100°Cstudied). Thesuperposition of the phase diagrams with the conversion–temperature trajectoriesduring cure provided an explanation of the morphologies generated. © 2001 John Wiley &Sons, Inc. J Appl Polym Sci 81: 889–900, 2001