蚕丝纤维增强聚乳酸体系中柱晶的形成及结构分析

采用溶液法制备聚乳酸(PLA)薄膜,并利用偏光显微镜在线研究了不同温度及不同牵引速率下,单根蚕丝纤维(SF)诱导PLA柱晶的形成,并利用显微红外光谱表征柱晶结构.结果表明,当牵引速率大于或等于临界速率时,纤维表面有连续的柱晶生成,反之柱晶不连续;当牵引速率大于临界饱和速率时,柱晶的结晶度和取向度分别趋于稳定值;在等温条件下,随着牵引速率的增大,柱晶的成核诱导期缩短,晶体的成核密度增大,取向度增加;当牵引速率一定时,与130℃相比,温度为120℃时形成柱晶的成核诱导期较短,成核密度更大,结晶度更高,柱晶层的生长更快.

Formation and Structure Analysis of Interfacial Cylindrites Induced by Silkworm Silk Fiber in Poly( lactic acid) Based Composites

Thin films of poly ( lactic acid ) ( PLA ) were prepared using solution method. At different temperatures and fiber-pulling speeds, the morphology of cylindrites induced by a single silkworm silk fiber (SF) in PLA films was investigated by polarized optical microscopy(POM) and Fourier transform infrared spectroscopy( FTIR) . The results show that there is a critical fiber-pulling speed, above which the continuous cylindrites structure could be generated on the fiber surface, whereas discontinuous cylindrites would form at a speed lower than that value. Besides, there also exists another special speed defined as saturation fiber-pulling speed, and once the pulling rate exceeds that value, the degree of crystallization and orientation will reach a plateau. Moreover, at the same temperature, the induction period of cylindrites nuclei reduces and its nuclei density and the orientation increase with raising the fiber-pulling speed; under a given fiber-pulling speed, compared to 130 ℃, the induction period of cylindrites is shorter, and its nuclei density, growth rate as well as final crystallinity are much higher at 120 ℃.