聚(L-乳酸)的成纤模压增强

用成纤模压法制备了弯曲强度和剪切强度分别为 2 50～ 2 80MPa和 1 70～ 1 85MPa的聚 (L 乳酸 )(PLLA)园棒 .由于PLLA对热的不稳定性 ,在模坯制备过程中 ,PLLA的分子量下降 65%～ 70 % ,但模压过程对分子量影响较小 .扫描电子显微镜 (SEM)显示PLLA模坯在模压过程中发生了取向形变并形成纤维结构 ,这是PLLA棒材的力学性能得以增强的主要原因 .差示扫描量热 (DSC)分析和X 射线衍射 (XRD)分析表明PLLA模压成棒后 ,PLLA的结晶熔点下降 ,微晶尺寸变小 ,而结晶度增大 .

ENHANCEMENT OF POLY(L-LACTIDE) BY FIBRILLATED COMPRESSION MOLDING

Poly(L-lactide) (PLLA) rods with high strength were prepared by fibrillated compression molding in a special mold designed for this purpose.It was showed that this compression molding method had a great effect on enhancement of the mechanical strength of the molded materials. PLLA rods ( 3 2mm) with bending strength and shear strength of 250～280 MPa and 170～185 MPa respectively were obtained by using PLLA materials of molecular weight (Mv) ranged from 53×10 4 to 76×10 4 and compression molding at 140℃.The molecular weight of PLLA reduced by 65% to 70% in the process of preparing billets due to its thermal instability,but the influence of compression molding on the molecular weight was not significant.SEM observation showed that the PLLA billet underwent oriented deformation and formed fibrous structure during compression molding,and this is the reason why the mechanical strength of the PLLA rods can be enhanced.Analytical results of differential scanning calorimetry (DSC) and X\|ray diffraction (XRD) indicated that after compression molding,the melt temperature of PLLA crystals decreased while the degree of crystallinity increased.