Polymer Blends Composed of Poly (D,L-lactic acid)/L-Lactide Copolymers

The improvement of mechanical properties of poly(D,L-lactic acid) (PDLLA) was attempted by blending PDLLA with L-lacticle (LLA) copolymers containing an elastic comonomer, either epsilon-caprolactone (CL) or trimethylenecarbonate (TMC). Immiscible blends of PDLLA/LLA-CL and PDLLA/LLA-TMC were obtained. The structure and properties of polymeric systems containing the lactide unit as a major component were studied by GPC, H-1 NMR, TEM, DSC, DMA, and tensile tests. By comparisons among the lactide copolymers with a homogeneous distribution of the elastic comonomer, CL or TMC, in the system and the blends composed of PDLLA/LLA copolymers with a heterogeneous distribution of the elastic comonomer in the system, we clearly demonstrated that the latter had better mechanical properties than the former at the same elastic comonomer concentrations in the system. These blends demonstrated an excellent property of shape preservation as well.