Effect of Copolymer Composition on the Dynamic Mechanical and Thermal Behaviour of Butyl Acrylate‐Acrylonitrile Copolymers

Abstract

AbstractThis article reports data on the dynamic mechanical and thermal behaviour of butyl acrylate‐acrylonitrile copolymers and their variation with copolymer composition. The copolymers were prepared by emulsion polymerisation techniques, using potassium peroxodisulfate initiator at 80 ± 2 °C. Films were prepared from the latex by casting and analysed by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). For copolymer with 0.7 weight fraction of butyl acrylate the dynamic mechanical behaviour was identical to the synthetic rubber NBR (acrylonitrile‐butadiene rubber), such that the storage modulus shows a rapid decay with increasing temperature. The damping characteristics, as indicated by the tan δ value, increased as the weight fraction of butyl acrylate in the copolymer increased. The dynamic mechanical data has been analysed with the WLF‐Equation to study the time‐temperature relationship. The dynamic mechanical properties and glass transition data point to the formation of a copolymer, whose properties vary with acrylonitrile content. Thermogravimetric analysis revealed that weight loss occurring at a particular temperature decreases, along with the decomposition rate, with increase in acrylonitrile content. The activation energy (Ea) for the decomposition was calculated using the Coats & Redfern equation. When temperatures for 10% copolymer decomposition are compared from TGA data, the acrylonitrile rich copolymer starts decomposing at a lower temperature, but the rate of decomposition is slower and yields higher char yields.Effect of copolymer composition on the variation of tan δ (max) at a measuring frequency of 1 Hz.magnified imageEffect of copolymer composition on the variation of tan δ (max) at a measuring frequency of 1 Hz.