Effects of Thermal History and Physical Aging on Thermal Properties of Poly-L-Lactide

Poly-L-lactide (PLL) represents a major bioabsorbable polymer used in implants. Depending on its thermal history, PLL can exhibit three discernible thermal transitions upon heating: glass transition, recrystallization, and melting. These transitions are pertinent to the polymer's short- and long-term performance. Accordingly, properties of medical devices made of PLL may be altered and optimized when subjected to different thermal environments. In the present study, differential scanning carlorometry was used to study effects of thermal treatment and physical aging on thermal properties of PLL. Heat treatment was conducted at three different temperatures. Physical aging was performed at room temperature for five different time intervals. Results indicate that glass transitions and level of crystallinity were affected significantly. The polymer crystallinity can be greatly increased by thermal treatment, which may ultimately improve its mechanical properties, as well as strength retention, and absorption profile. Relevance of these results to the physical events taking place during the treatment, and their impact on post-processing and property change of fabricated articles are discussed.