RAFT mediated miniemulsion copolymerization of ethylene and BMA and their non-isothermal model-free kinetic analysis

Abstract

Miniemulsion copolymerization of ethylene and butyl methacrylate (BMA) was carried out at 60 °C using 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid as the reversible addition fragmentation chain transfer (RAFT) agent, sodium dodecyl sulphate as emulsifier and potassium per sulphate as free radical initiator under extremely low ethylene feed pressure of 5–20 bar. In the absence of a co-stabilizer, very stable emulsion was obtained, wherein the RAFT agent acted both as the chain transfer agent and as the co-stabilizer. FT-IR as well as NMR analysis established the formation of poly(ethylene-co-BMA) copolymer nanoparticles. The SEM analysis was used to study the morphological behaviour of poly(ethylene-co-BMA) copolymer nanoparticles. DLS analysis confirmed that the particle diameter Zavg of copolymer nanoparticles is in the range 100–140 nm and confirmed miniemulsion polymerization. In order to establish the stability of copolymers against thermal degradation, the kinetics and mechanism of thermal degradation of copolymers were investigated by thermogravimetric analysis. Thermogravimertic analysis established that thermal decomposition of poly(ethylene-co-BMA) copolymer nanoparticles occurred in the range 250–450 °C. This range is lower than the decomposition temperature of neat polyethylene (350–580 °C). Kinetic parameters were determined according to the model-free approaches of Friedman and Flynn–Wall–Ozawa. The multivariate nonlinear regression analysis was performed to determine the kinetic model and the corresponding kinetic triplets.