Thermal degradation kinetics of poly(acrylate/α-methyl styrene) copolymers

Abstract

The poly(acrylate/α-MeSt) copolymers were prepared by emulsion polymerization of butyl acrylate (BA), 2-ethylhexyl acrylate (2-EHA) and α-methyl styrene (α-MeSt). The contents of α-MeSt units combined into the copolymers were confirmed by 1H-NMR. In order to clarify the thermal degradation phenomenon of the copolymers differential scanning calorimetry (DSC) was used to monitor the initial decomposition of the copolymers at low temperatures without obvious weight loss, and gel permeation chromatography (GPC) was used to characterize the molecular weights of the copolymers and the thermally treated ones. The thermal degradation behavior of these copolymers was investigated by thermogravimetry (TGA), and the thermal degradation kinetics was systematically investigated by both Kissinger method, Flynn–Wall–Ozawa (FWO) method and Kissinger–Akahira–Sunose (KAS) method. The GPC and DSC measurements showed that bond breaking of the poly(acrylate/α-MeSt) copolymers occurred at a relatively low temperature compared with neat polyacrylates; the thermal degradation kinetics analysis verified that both the activation energy and pre-exponential factor increased with increasing the content of α-MeSt units in the copolymers; consequently, the decomposition reaction rate constant of the poly(acrylate/α-MeSt) copolymers increased with increasing the amount of combined α-MeSt units in the copolymers when the degradation temperature was higher than 320 °C. FWO method and KAS method revealed that the value of the degradation activation energy of the copolymer sample with higher content of α-MeSt units was higher than that of the copolymer sample with lower content of α-MeSt units at the same conversion.