Dynamic mechanical behavior of oriented semicrystalline polyethylene terephthalate

The dynamic mechanical behavior of molecularly oriented semicrystalline pol yethylene terephthalate (PET) induced via the equal-channel angular extrusi on (ECAE) process was investigated. Dynamic mechanical analyses in both tor sional mode and bending mode were utilized. The results indicate that the E CAE-oriented PET has a higher dynamic storage modulus above the glass-trans ition temperature than that of the reference (control sample). The combined effect of molecular orientation and crystallinity is responsible for the c hanges in the primary and secondary relaxations of PET. Further analyses sh ow that the shifting and broadening of the primary and secondary peak posit ions in oriented PET are mainly due to the amorphous-phase orientation beca use the crystallinity of PET decreases upon the ECAE processing A good corr elation was found between the structural anisotropy and the dynamic mechani cal properties. (C) 2001 John Wiley & Sons, Inc.