Thermal decomposition of acrylonitrile copolymers investigated by direct pyrolysis in the mass spectrometer

The thermal behaviour of copolymers of acrylonitrile containing up to 15 wt.‐% of methyl acrylate (MA), methyl methacrylate (MMA), vinyl acetate (VA), and vinyl bromide (VB) units, was investigated by gradually increasing the temperature of a polymer sample placed in the ion source of a mass spectrometer (MS). The resulting pyrolytic processes (time‐temperature resolved) were analyzed by detecting the volatile decomposition products formed. Several decomposition processes were ascertained. Bromine derivatives evolution from the VB copolymer chain occurs already at 160–200°C. The thermal decomposition of the pendant ester groups in the MA and MMA copolymers occurs in the temperature range of 200–260 °C. Typical polyacrylonitrile (PAN) decomposition fragments were detected in the 240–300 °C range in all the copolymers investigated. Acetic acid units are evolved from the VA copolymer simultaneously to the PAN thermal fragments. Heterocyclic compounds originated from the ladder structures appear beyond 300°C.