Improvement of thermal and mechanical properties of poly(L-lactic acid) with 4,4-methylene diphenyl diisocyanate

In this study, the thermal and mechanical properties of biodegradable poly(L-lactic acid) (PLA) were improved by reacting with 4,4-methylene diphenyl diisocyanate (MDI). The resulting PLA samples were characterized with Fourier transformation infrared spectrometer (FT-IR). The glass transition (T.) and decomposing (Td) temperature of the resulting products were measured using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. The tensile properties were also measured with a tensile tester. The results show that when the molar ratio of -NCO to -OH was 2:1, the T-g value can be increased to 64 degrees C from the original 55 degrees C, and the tensile strength increased from 4.9 to 5.8 MPa. This demonstrated that by reacting PLA with MDI at an appropriate portion, both the thermal and mechanical performance of PLA can be increased. Copyright (c) 2006 John Wiley & Sons, Ltd.