Structure development and physical properties achieved in the drawing and/or annealing of PEN fibers

Autor: Ming Liu, Gang Wu, John A. Cuculo, Xiaoning Li
Rok vydání: 2000
Předmět:
Zdroj: Journal of Polymer Science Part B: Polymer Physics. 38:1424-1435
ISSN: 1099-0488
0887-6266
DOI: 10.1002/(sici)1099-0488(20000601)38:11<1424::aid-polb20>3.0.co;2-g
Popis: As-spun poly(ethylene-2,6-naphthalate) (PEN) fibers (i.e., precursors) prepared from high molecular weight polymer were drawn and/or annealed under various conditions. Structure and property variations taking place during the treatment process were followed via wide-angle X-ray scattering (WAXS), small-angle X-ray scattering, differential scanning calorimetry (DSC), and mechanical testing. Both the WAXS and DSC measurements of the cold-drawn samples stretched from a low-speed-spun amorphous fiber indicate that strain-induced crystallization can occur at a temperature below the glass-transition temperature and that the resultant crystal is in the α-form modification. In contrast, when the same precursor was subjected to constrained annealing, its amorphous characteristics remained unchanged even though the annealing was performed at 200 °C. These results may imply that the application of stretching stress is more important than elevated temperatures in producing α-form crystallization. The crystalline structure of the hot-drawn samples depends significantly on the morphology of the precursor fibers. When the precursor was wound at a very low speed and in a predominantly amorphous state, hot drawing induced the formation of crystals that were apparently pure α-form modification. For the (3-form crystallized precursors wound at higher speeds, a partial crystalline transition from the β form to the a form was observed during the hot drawing. In contrast with the mechanical properties of the as-spun fibers, those of the hot-drawn products are not improved remarkably because the draw ratio is extremely limited for most as-spun fibers in which an oriented crystalline structure has already formed.
Databáze: OpenAIRE
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