Structure and Mechanical Properties of Sequential Interpenetrating Polymer Networks. I. Poly(ethyl acrylate)/Poly(methyl methacrylate) System

Abstract

Interpenetrating polymer networks (IPNs) composed of poly(ethyl acrylate) (PEA) and poly(methyl methacrylate) (PMMA) were prepared by two different methods of composition control: control of the swelling ratio of the first PEA network with a MMA second monomer mixture subsequently allowed to polymerize and become crosslinked upto the point of completion (SW-series), and control of the conversion of MMA absorbed in the PEA network (CV-series). The dynamic mechanical properties and stress-strain behavior of these IPNs were examined. In the process of IPN formation, it is likely that the MMA first forms microgels in the PEA network, and these microgels eventually interconnect to form a fully interpenetrating network having microheterogeneous nodular domains. The glassy PMMA microdomains impart a filler effect (similar to that found in filled elastomers). Semi- and full-IPNs of 75 wt% PMMA content in which PMMA was uncrosslinked and crosslinked, respectively, were also prepared and the mechanical properties were examined. Viscoelastic behavior of both semi- and full-IPNs is linear with small deformation, but nonlinear when subjected to large and/or high speed deformation. The full-IPN was stronger and stiffer than the semi-IPN.