Structure development in the phenolic resin/poly(methyl methacrylate-co-ethyl acrylate) copolymer blends

Abstract

Single-phase mixtures of phenolic derivatives with three poly(methyl methacrylate-co-ethyl acrylate) copolymers [P(MMA-co-EA)s] were cured in the presence of hexamethylenetetramine and the reaction kinetics and phase-separation processes during cure were investigated by differential scanning calorimetry (DSC), light scattering, and optical microscopy (OM). DSC measurements revealed that the higher the fraction of multifunctional phenols in the total phenols the lower the conversion at gelation in the phenolic-rich phase. The time variation of the light-scattering profile during cure demonstrated the characteristic feature for spinodal decomposition. OM observation revealed that a cocontinuous two-phase structure appeared after a certain time lag and coarsened to a spherical domain structure consisting of phenolic resin particles dispersed in the P(MMA-co-EA)s matrix. The periodic distances, Λm, in the phase-separated structure changed with curing time: (1) The higher the component of MMA in P(MMA-co-EA)s and (2) the higher the fraction of multifunctional phenols in the total phenols, the smaller the Λm. These results may imply that the phase separation is suppressed by the faster gelation in the phenolic-rich phase so that the phase-separated structure can be fixed by the network formation in the phenolic-rich phase at the early stage of spinodal decomposition. This results in a two-phase structure with a shorter periodic distance. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1829–1837, 1998