Preparation and Physical Properties of Hollow Polyester Filaments with High Breathability,Water Absorption and Release Rates

Abstract

This paper reports the preparation of hollow polyester filaments with high water absorption and release rates, and the study of their physical properties using differential scanning calorimetry, thermogravimetric analysis, density gradient, gel permeation chromatography, rheometry and statistical regression analysis.

Four readily soluble poly(ethylene glycol)-modified cationic dyeable poly(ethylene terephthalate) (PEG-CDPET) polymers were prepared, with 3 mol % of the sodium salt of dimethyl 5-sulfo-isophthalate (SIPM). The poly(ethylene glycol) (PEG) contents were 3 and 6 wt% and the number-average molecular weights ( $\bar{M}\mathrm{n}$ ) of the PEG were 600 and 8000 (g/mol).

Blends of regular PET and PEG-CDPET were spun into hollow filaments. These hollow filaments were then drawn and treated with aqueous sodium hydroxide. The crystallinity of the PEG-CDPET polymers declined as the PEG content increased, given a fixed SIPM content. Furthermore, the crystallinity of the PEG-CDPET polymers declined as the $\bar{M}\mathrm{n}$ of the PEG increased for the same SIPM and PEG contents. The SIPM and PEG segments did not change the original PET unit cell. The sodium sulphonate (–SO₃Na) functional groups and the PEG molecules were only on the crystal surface and in the amorphous regions. Obviously, the rate constants for alkaline hydrolysis were in the order: PEG-CDPET polymer<<CDPET polymer<regular PET polymer. The water-absorption and release and the heat retention properties of alkali treated PET/PEG-CDPET polyblend hollow filaments were better than those of the regular PET filaments. The porous nature of the large filaments (from 0.02-1 μm in diameter) was observed after alkali treatment of the PET/PEG-CDPET polyblend hollow filaments. Additionally, the hollowness of the PET/PEG-CDPET polyblend filaments was observed to increase from 40 to 42% after alkali treatment.