PET Filaments with Radially-Differentiated Structure

Abstract

An undrawn polyester monofilament was subjected to sequential solvent and thermal/stress crystallization during drawing to produce a radially-differentiated structure. Solvent-induced crystallization of outer regions of the filament was achieved using methylene chloride or dimethylformamide at room temperature. The thermal/stress crystallization of the filament core was conducted at a draw ratio of 4.0 at temperatures ranging from 90 to 120°C. The resulting filaments were characterized by measurements of density and mechanical properties, by wide-angle x-ray diffractometry, and by scanning electron microscopy. The structure of the outer regions of these novel filaments consists of highly- deformed spherulites, while the inner core is fibrillar in character with well-developed orientation and crystallinity. The extreme outer surface appears to be cavitated, leading to extremely high surface areas. It is proposed that such radially- differentiated filaments will have the combined desirable properties of spherulitic and fibrillar morphologies, such as high liquid-retention values, improved adhesion, and high strength.

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