THE OXIDATIVE DECOMPOSITION OF POLY(METHYL METHACRYLATE)-CROSS-LINKEDPOLY(BUTYL ACRYLATE) CORE-SHELL POLYMERS

The thermo-oxidative stability of polymer samples based on submicromet ric three-layer bead particles was evaluated by dynamic thermogravimet ry (TG). Polymer particles synthesized in emulsion consist of a poly(m ethyl methacrylate) core, a butyl acrylate crosslinked copolymer inter layer and a methyl methacrylate butyl acrylate copolymer shell. The co mparative mass loss study in oxygen and nitrogen leads to the followin g conclusions. Oxygen retards the decomposition to volatiles of the po lymer sample isolated from the emulsion in powder form at lower temper atures at the beginning of the process. The second stage of the TG rec ord which is relevant to the mass loss of the butyl acrylate copolymer shows a higher rate of formation of volatiles. In oxygen, the densifi ed polymer samples prepared by melting the particle polymer powder do not show a substantial difference compared to the TG curves observed f or powder samples. However, the thermodegradation in nitrogen is shift ed by more than 60 degrees C to higher temperatures. We explain the di fferent course of the TG curves by a denser packing of core-shell part icles in the processed samples. The diffusion of reaction products fro m the reaction cage is slowed down with a positive effect on thermosta bility. Oxygen acts in the opposite way through the oxidative polymer chain scission of macromolecules and increases the rate of initiation of depolymerization. Increasing the rate of heating of the sample in o xygen only has a small effect on shifting the volatilization to higher temperatures. This is less evident than in nitrogen. (C) 1997 Elsevie r Science Limited.