Mechanical,Thermal,and Thermomechanical Properties of Propionylated Cotton Yarn

Abstract

Mechanical, thermal, and thermomechanical properties of propionylated cotton yarn of varying degree of substitution (DS) are reported. The properties examined were yarn number, breaking strength, elongation, twist, tensile stiffness, differential thermal analysis (DTA) and thermogravimetric analysis (TGA) behavior and stiffness, elastic recovery, and work recovery at elevated temperatures.

Breaking strength, on the basis of the tex of the control yarn, is within 84% of the control up to a DS of 2.0. Elongation at break generally increases and tensile stiffness decreases with DS. A great improvement of toughness is observed with propionylation, except in cases where the sample is degraded by a two-stage preparatory treatment. DTA tracings show exothermic transitions consistent with recombination and inter reaction of cellulose fragments, and the interpretations are amply supported by TGA results. Stiffness, work recovery, and elastic recovery measured at the temperature range of 30-155°C all show a glass transtion at 120 ± 10°C. The rate of stiffness loss increases with increasing substitution. The elastic recovery and work recovery curves are consistent with the loss of lateral order at higher substitution. In all the measure ments, the curves in the second cycle of heating and cooling reveal the same features as those of the cooling phase of the first cycle but are more symmetrical due to stabilization of yarn structure.