Preparation of long-chain branched polyethylene terephthalates (PETs), and crystallization behaviors, thermal characteristics, and hydrolysis resistance of their biaxially stretching films

Long-chain branched polyethylene terephthalates (PETs) composed of ethylene glycol, terephthalic acid, trimesic acid, and their biaxially stretching films with superior crystal sizes and inferior crystal growth rates, melting points, equilibrium melting points, fold surface free energies, and orientation parameters compared to common PET were manufactured by T-Die extrusion and biaxially stretching treatment. In order to evaluate the hydrolysis resistance for biaxially stretching films of lab-made long-chain branched PETs, we examined their half-life period of elongation, defined as the time for which the films could retain their elongation at 50% during the hydrolysis procedure under conditions of 100% humidity, 1.5 atm pressure and 120 °C. Experimental results revealed that biaxially stretching film of long-chain branched PET II had high potential as an optical substrate for optoelectronic devices because its half-life period of elongation was 58 compared to 21 h for common PET.