Effect of Hot-Drawing on Morphology and Mechanical Property Development in Random and Block Terpolyester Fibres base on L-Lactide, ε-Caprolactone and Glycolide

Biomedical Polymers Technology Unit, Department of Chemistry, Chiang Mai University* Department of Physics and Polymer Science Centre, University of Reading, UK**
○Wasinee Channuan* Jintana Siripitayananon* Robert Molloy* Geoffrey R Mitchell**

Terpolymers of L-lactide (LL), ε-caprolactone (CL) and glycolide (G) were synthesized for use as absorbable surgical sutures. Random (Mw = 61,000) and block terpolymers (Mw = 47,000) with a composition ratio of LL:CL:G 75:20:5 mol % were studied for comparison. The crystallization behaviour of the terpolymers was investigated by 4-circle X-ray diffractometry, optical microscopy, and confirmed by DSC. The results showed that the block terpolymer crystallized at a higher rate of about twice that of the random due to the greater regularity of its end-blocks but gave approximately the same maximum level of crystallinity. As-spun fibres of the terpolymers produced by melt spinning were almost completely amorphous with low crystallinity and molecular orientation. Hot-drawing under various conditions was employed to improve their mechanical properties. The analysis results from WAXD and DSC demonstrated that hot-drawing to a higher draw ratio induced molecular orientation and crystallization without any changes in the crystal structure within the fibre. The lamellar thickness of both terpolymers was invariant while the width increased with draw ratio, although the random fibre contained thinner crystallites. From mechanical testing, all tensile properties of the block terpolymer hot-drawn fibres were found to be better than those of the random fibres. The superior tensile strength of the block terpolymer fibre was attributed to its larger crystal size, higher crystallinity, lamellar stack structure, and greater molecular orientation in both the crystalline and amorphous phases.