A DEPOLARIZED LIGHT-SCATTERING STUDY OF THE PHASE-SEPARATION PROCESS IN AN EPOXY-ELASTOMER BLEND

Phase separation between two or more isotropic polymers is usually stu died by unpolarized or polarized light scattering (SALS). Depolarized SALS has never been used, but it is also able to bring useful informat ion about the kinetics and mechanisms of the phase separation. Such a new technique is tested here by studying the evolution of a phase sepa ration in a pseudo-binary mixture of bis-phenol A diglycidylether (epo xy monomer), a cycloaliphatic diamine (comonomer or cross-linking agen t) and an epoxy terminated butadiene-acrylonitrile random copolymer (a dditive). The depolarized light scattering patterns during the phase s eparation have four lobes positioned at 45 degrees of the position of the polarizers. The position of the lobes does not vary with time, sug gesting that the mechanism of spinodal decomposition is responsible fo r the phase separation. The resulting periodic distance between compos ition fluctuations is calculated from the position of the lobes using two methods. It was found in agreement with the distance deduced from the position of the scattering ring observed in unpolarized light scat tering. (C) 1997 Elsevier Science Ltd.