Heat - Mechanically Induced Structure Development in Undrawn Polyester Fibers

The performances of the non-isotropic polymer systems strongly depend on their super molecular structure (Wu et al., 2001; Shabana, 2004; Keum & Song, 2005; Ziabicki & Jarecki, 2007; Sulong et al., 2011). The wide application and consequently higher production of flexible chain fiber forming polymers, in particular poly (ethylene terephthalate) (PET) is due to the possibility of the heat mechanical modification to obtain highly modular and high strength materials from them (Llana & Boyce, 1999; Bai et al., 2000; Dupaix & Boyce, 2005; Guzzato et al., 2009). PET is an essential engineering polymer with properties strongly depending of the degree of crystallinity and the perfection of crystal phase, too. The effects of some basic parameters of the heat mechanically treatment such as strain force extension rate and temperature on the structure development of PET have been studied using different methods as differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS) (Kong & Hay, 2003; Zhang et al., 2004; Karagiannidis et al., 2008; Raabe et al. 2004), dynamic mechanical analysis (Ma et al., 2003), laser irradiation (Wijayathunga et al., 2007) and other. The optimal performance of the high-temperature orientation modification is a complicated and still not sufficiently well studied process. The simultaneous mechanical and thermal modification however is extremely complex phenomenon occurring on the basis of statistical probabilistic processes, as are also the possible results from it. In this sense the results from variations of heat mechanical modification are unpredictable not unique and often very different, contradictory and unexpected. Moreover for each specific object and purpose exist additional conditions, and therefore needed special study of orientation thermal treatment for the obtaining of best mechanical performance. If the samples simultaneous heat mechanical modification (SHMM) is carried out without accounting and control of a number of events, processes and parameters the results can easily prove contrary to the expectations. And to make the results from STMM easily predictable, susceptible to control and allowing obtaining of materials with improved predefined wanted properties it is necessary in depth study on the nature, mechanism and kinetics of the justifying processes and the relationship between them. Therefore the study of these processes is a permanent "ever green" interest in the polymer physics. One of the most interesting from this point of view objects are polyethylene terephthalate fibers. There are varieties of investigations of the affects of the thermal and mechanical treatments on the