The effect of heat setting on the structure and mechanical properties of poly(ethylene terephthalate) fiber. I. Structural changes

Abstract

SynopsisWe report structural changes in commercial multifilament poly(ethy1ene terephthalate) (PET) yarn when it is heat set in silicone oil over a range of temperatures between 100 and 220°C for times ranging from 1 min to 1 hr, while the yarn was (1) free to relax, and (2) held taut at constant length. In one case, viz., a sample heat treated for 1 hr, the cooling time was also varied to study the effect of rate of cooling. The free-annealed and taut-annealed samples showed considerable differences. The predominant role of the temperature of heat setting on structure is discussed in detail. There are considerable changes in the amount and orientation of the amorphous phase, and these will be shown to have important influence on mechanical properties in subsequent reports.

Crystalline structure of poly(ethylene terephthalate) filaments

“…Gupta and Kumar 26 reported an increase in the crystallite size of PET fibers due to heat setting and stated that the results for crystallite size from (100) plane show similar trends to those for the (010) plane. Fu et al 27 stated that annealing causes the crystallites in PET fibers to grow in all directions.…”

Polymer applications

“…The combination of birefringence measurements and other techniques has been demonstrated, for example, in studies of thermal shrinkage [24] and of the effect of heat setting on the mechanical properties of PET fibers [25]. Birefringence measurements are effective in providing a structural parameter which may be used to relate process variables to mechanical properties.…”

Structural evolution of poly(acrylonitrile‐co‐dimethyl itaconate) copolymer during thermal oxidative stabilization

“…The crystallinity (CI) of PAN and P(AN-DMI) was calculated from the XRD data using equation as follow [22] :…”