Thermoplastic composites of polystyrene with wood fibre based graft polymers as reinforcing agents

Abstract

The results presented in this study show that manganic pyrophosphate, over a wide range of reaction conditions, is an efficient initiator for grafting styrene onto wood fibres. Selective extraction of polystyrene homopolymer using benzene showed that grafting efficiencies were high in almost all cases. The grafting parameters can be varied substantially by adjusting the reaction conditions. From the discussion in the previous chapter, the following conclusions may be drawn:

An initiator concentration of 2.0 mmol?L?¹ yields maximum polymer loading, total conversion, and grafting efficiency. High temperatures do not significantly contribute to improvements in grafting parameters; a temperature of approximately 40?°C yields satisfactory grafting results. Polymer loading and grafting efficiency increase with increasing monomer concentration; however, total conversion decreases sharply.

The addition of grafted wood fibres to a polystyrene resin improves both the tensile strength and tensile impact strength of polystyrene. The observed improvement in mechanical properties suggests enhanced interfacial interaction between the wood fibres and the polystyrene matrix. Through grafting, polymer chains become covalently bonded to the wood fibres. As a result, cohesive forces between the grafted polymer chains and the polystyrene matrix help to overcome phase separation between wood fibres and polystyrene to a certain extent.