The influence of morphology on the (hydrolytic degradation of as-polymerized and hot-drawn poly (L-lactide))

The influence of morphology on the hydrolytic degradation behavior of poly( L-lactide) has been studied. High molecular weight and highly crystalline a s-polymerized poly(L-lactide) was obtained in high yields through melt poly merization. Poly(L-lactide) fiber with a draw ratio of 5.6 was obtained by hot-drawing solution-spun fiber. During the bulk degradation of as-polymerized poly(L-lactide), a rapid decr ease of molecular weight and tensile properties was observed. This could be explained by the morphology of the material and the presence of thermal st resses and subsequent generation of microcracks. The lamellar crystallites in as-polymerized poly(L-lactide) appeared to be very stable towards hydrol ysis. The resorption time of high molecular weight as-polymerized poly(L-la ctide) in vivo was estimated at 40-50 yr by extrapolation of molecular weig ht data. Hot-drawn poly(L-lactide) fiber showed exceptional hydrolytic stability und er a static load and substantially retained its mechanical properties over a period of more than 5 yr. The high perfection of the crystalline fiber an d the elimination of micro-voids obtained by hot-drawing prevented penetrat ion of water and induced surface erosion of the fiber.