ORIENTED NONCRYSTALLINE STRUCTURE IN PET FIBERS PREPARED WITH THREADLINE MODIFICATION PROCESS

The development of an oriented noncrystalline phase in a semicrystalli ne polymer filament has been studied via X-ray scattering. These uniqu e PET fibers contain a relatively high noncrystalline content and also have high tenacity, high modulus, and low breaking elongation. Fiber properties were found to be very responsive to the oriented amorphous phase content. This phase was utilized for interpreting noncrystalline orientation in PET fibers produced by a new extrusion technique. Here , the oriented noncrystalline regions in a series of PET fibers varies from 6% to 63% depending strongly on the production conditions. In pa rticular, samples produced with a newly developed threadline modificat ion process possess a high content of oriented noncrystalline polymer. Measurements such as dynamic and static mechanical properties have be en performed on various samples, and these properties are related to t he oriented noncrystalline phase. The results provide direct evidence for the existence of highly oriented noncrystalline material in these unique PET fibers spun with a threadline modification process. (C) 199 6 John Wiley & Sons, Inc.