Crystallinity and mechanical properties of optically pure polylactides and their blends

Abstract Nonisothermal solidifications of medical‐grade polylactides were conducted on compression molding sheets, resulting in a variety of crystalline forms and different amounts of crystallinity. Both optically pure polylactides, poly (L‐lactide) (PLLA) and poly (D‐lactide) (PDLA), were found to crystallize at a low melting temperature α crystalline form. PLLA/PDLA blends were found to yield both α homocrystallites and 50°C higher melting temperature stereocomplex crystallites. The effects of processing conditions and blend composition on crystal heterogeneity and degree of crystallinity were studied. Tensile tests reveal for these polylactides Young's modulus values of 3.5–4.2 GPa, strength values of 62–71 MPa, and elongations at break of 1–5%, depending on blend composition and crystallinity. POLYM. ENG. SCI. 45:745–753, 2005. © 2005 Society of Plastics Engineers