Transesterification of Poly(Ethylene Terephthalate) and Bisphenol-A-Polycarbonate

Abstract

Blends of Poly(ethylene terephthalate) (PET) and bisphenol-A-polycarbonate (PC) have been made by solution and melt blending and these blends were subject to isothermal heating to induce a transesterification reaction. The raw materials and products of this reaction have been studied by a variety of different methods to ascertain the chemical, physical and mechanical properties they possess. The conclusions drawn are listed below. PET and PC are immiscible but are compatibilised by transesterification. Transesterification is a second order reversible process and is fast only when water is present, when absent the rate of transesterification is so slow that little or no reaction is observed in after 60 minutes at 300 c. When water is present in the blend significant chain scission and degradation takes place, this is not observed in the absence of water• The material obtained from melt blending has a molecular weight higher than that of commercial PET and it is possible to increase it further by standard solid state polymerization techniques. The PC concentration in PET is critical to the existence and extent of crystallisation. PET blends containing 10% PC are not significantly stronger or weaker than commercial PET and perform very similarly to the yield point. PET blends containing 10% PC are less ductile than commercial PET and will therefore fail sooner when they have yielded under tension. PET blends containing 10% PC do not injection mould as well as commercial PET under conventional procedures for PET, surface crazing and voiding is observed