Preparation of a novel oligomer type compatibilizer for polypropylene/polystyrene blend

Abstract

A polystyrene–g–2,2,6,6-tetramethylpiperidine 1-oxyl radical (PS–g–TEMPO) copolymer was formed during thermal-oxidative degradation of PS/hindered amine light stabilizer (HALS) under heat treatment by thermal equilibrium. The optimum preparation condition was identified at 150 °C for 21 h by assessment of the temperature and aging time dependences of the molecular weight and thermal properties. The optimized copolymer was reacted with polypropylene (PP). A PS–g–PP grafted copolymer-type compatibilizer was reactively prepared with the copolymer/PP at 200 °C melt mixing temperature. The tetrahydrofuran-soluble part of the PP/PS/PS–g–TEMPO blend was analyzed as the PS–g–PP copolymer. The PS–g–PP showed a broad melting peak in the range from 125 °C to 160 °C. The PP grafting ratio was approximately 4%, as calculated by pyrolysis gas chromatography mass spectrometry (Py-GC/MS) analysis. The reactive polymer blend of the PP/PS/PS–g–TEMPO showed significant improvement in mechanical properties and ductile fracture surface as compared with PP/PS. The HALS loading easily produced an excellent compatibilizer for PP/PS mechanical improvement.