ABSTRACT:The structure and properties of fibers prepared from copolymers of poly(ethylene terephthalate) (PET) in which 2-methyl-1,3-propanediol (MPDiol Glycol is a registered trademark of Lyondell Chemical Company) at 4, 7, 10, and 25 mol% was substituted for ethylene glycol were studied and compared with those of PET homopolymer. Filaments were melt spun over a range of spinning conditions, and some filaments that were spun at relatively low spinning speeds were subjected to hot drawing. The filaments were characterized by measurements of birefringence, differential scanning calorimetry (DSC) crystallinity, melting point, glass transition temperature, wide-angle Xray diffraction patterns, boiling water shrinkage, tenacity, and elongation to break. Filaments containing 25 mol% MPDiol did not crystallize in the spinline at any spinning speed investigated, whereas the other resins did crystallize in the spinline at high spinning speeds. However, compared with PET homopolymer, increasing substitution of MPDiol reduced the rate at which the crystallinity of the melt spun filaments increased with spinning speed and reduced the ultimate crystallinity that could be achieved by high-speed spinning. The rate of development of molecular orientation, as measured by birefringence, also decreased somewhat with increasing MPDiol content. Shrinkage in boiling water decreased at high spinning speeds as the amount of crystallinity increased; however, the shrinkage decreased more slowly with increase in spinning speed as MPDiol content increased. Tenacity also decreased slightly at any given spinning speed as MPDiol content increased, but there was no significant effect on elongation to break. The addition of MPDiol in amounts up to 7 mol% increased the maximum take-up velocity that could be achieved at a given mass throughput. This result indicates that the use of higher spinning speeds could potentially increase the productivity of melt spun yarns. Copolymer filaments spun at low speeds were readily drawn to produce highly oriented fibers with slightly less birefringence, crystallinity, and tenacity than similarly processed PET homopolymer. Preliminary dyeing experiments showed that the incorporation of MPDiol improved the dyeability of the filaments.

Quiescent melt crystallization rates of various polyolefins including high density polyethylene (PE), isotactic form of polypropylene (PP), polybutene-1 (PB1), and poly(4-methyl pentene-1) (P4MP1) were investigated under both isothermal and nonisothermal conditions using differential scanning calorimetry (DSC). The order of overall crystallization rates under quiescent conditions from fast to slow was found to be: PE, P4MP1, PP and PB1. The Avrami equation was used to analyze isothermal and nonisothermal crystallization processes, respectively. In order to compare relative crystallization rates of these polymers, continuous cooling transformation curves for each polymer under nonisothermal condition as well as the plot of crystallization half-time as a function of crystallization temperature under isothermal conditions were constructed. Comparisons were made of the relative rate of crystallization of the different isotactic polyolefins with each other and with reports in the literature. Isotactic polyolefins with linear side groups crystallize increasingly more slowly as the side group lengthens with polypentene-1 (PPT1) and polyhexene-1 (PH1) crystallizing even more slowly than PB1. It is notable that P4MP1, which has isobutyl as a bulky side group, and apparently poly(3-methyl butene-1) (P3MB1) showed fairly high crystallization rates.

We have studied the structural characteristics of the cross-sections of injection molded parts of various crystalline polyolefins including polyethylene (PE), isotactic polypropylene (PP), isotactic poly(butene-1) (PB1) and isotactic poly(4-methylpentene-1) (P4MP1). Polarized light microscopy, birefringence and wide angle x-ray diffraction pole figure analysis were used to investigate the samples. In most cases, high orientations were observed near the mold wall and isotropic molded part cores were found. However, highly oriented mold core regions were found in P4MP1. Significantly different types of crystalline orientation near the mold wall were observed among the various polyolefins. We represent the development of these differences through the components of a crystalline orientation tensor which represent changes in the state of orientation between melts in the mold prior to crystallization and the final crystalline molded part.

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