Thermal degradation of multilayer methacrylate-acrylate particle-bead polymer powders and melts

Abstract

The effect of the composition and form of polymer sample on a nonisothermal weight loss study of submicrometric multilayer polymer particles has been examined. Polymer beads consist of a poly(methyl methacrylate) (PMMA) core, poly(butyl acrylate) copolymer (BAC-co) network shell and a further layer of poly (methyl methacrylate) copolymer with butyl acrylate (MMA-co). Dynamic thermogravimetric curves show two stages for multilayer polymer powders and for particle polymer mixtures prepared by mixing emulsions before the freeze-thaw isolation of polymer. The first degradation step, due to PMMA depolymerization starts at a temperature 45 °C lower compared with degradation of the PMMA particle polymer powder alone. The polymer samples which were processed by melt stirring, press molded or even isolated from emulsions as transparent films before thermogravimetry analysis are more stable than polymer powders from emulsion. The weight loss of bulk samples proceeds smoothly in one stage like a one type polymer; nevertheless the PMMA is more sensitive to thermal degradation than the BAC-co network. The stabilization of PMMA in a blend with BAC-co in a bulk polymer sample is possibly due to the BAC-co compressed network which prevents PMMA depolymerization.