SYNTHESIS AND CHARACTERIZATION OF BRANCHED POLY(ETHYLENE-TEREPHTHALATE)

Branched poly(ethylene terephthalate)s (PET) were synthesised with a v ariety of molar masses and with a large range of degree of branching b y introduction of mono-, tri-(glycerol) and tetra-functional (pentaery thritol) comonomers to dimethyl terephthalate and ethylene glycol. The monofunctional alcohols, dodecanol and benzyl alcohol, were used as t erminating agents to minimise gelation. The effect of various reaction parameters, such as percentage glycerol or pentaerythritol and polyme risation time, on limiting viscosity number [eta] and weight average m olar mass ((M) over bar(w)) were investigated. The thermal behaviour o f branched PET was studied by differential scanning calorimetry; all s amples showed a characteristic double endothermic melting peak and the glass transition temperature was not observed. Some branched PETs wer e subjected to solid-state polymerisation to increase the molar mass o f previously prepared branched polymers. The solid-state polymerisatio n technique showed that the process not only promoted the molar mass b ut, more importantly, it increased the crystallinity of the polymer. O verall, the solid-state reaction rate was governed by initial molar ma ss, crystallinity, reaction temperature and time.