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Heat Setting of Polyethylene Terephthalate

1964; Volume: 21; Issue: 227 Linguagem: Inglês

10.1295/koron1944.21.166

1884-8079

Nobuo Ueda, S. Nishiumi,

Material Properties and Processing

Infrared and density measurements were made on unoriented and uniaxially oriented polyethylene terephthalate films after heat setting under various conditions.Each sample was subjected to dry-heating or steam setting for half an hour at temperatures ranging from 60°C to 220°C.The relationship between the degree of crystallinity (α) and optical densities (D) at 972, 845 and 794cm-1 is as follows:_??_or_??_α increases monotonously with temperature in the range 120°C to 200°C. In the case of dry-heat setting, minimum crystallization temperature for unoriented samples lies between 100°C and 120°C, while in steam setting this temperature is lowered to 80-100°C.The difference in crystallinity between dry-heat and steam set samples increases with setting temperature.For uniaxially oriented samples the following equation holds between dry-heat and steam setting temperatures which produce the same order of crystallinity;Td=1.16Tw-6.8 (80°C≤Tw≤180°C), where Td and Tw are the dry-heat and the steam setting temperatures, respectively.These phenomena suggest that on steam setting the interaction between polymer molecules in the amorphous region is weakened by penetration of water, and the thermal crystallization is thereby accelerated.