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采用多元环氧扩链剂(ADR)对聚乳酸(PLA)进行熔融扩链改性,得到PLA/ADR共混物。采用差示扫描量热仪(DSC)对共混物的熔体等温结晶行为进行表征和分析。结果表明:在110~120℃温度范围内,ADR的加入提高了PLA熔体的结晶速率;随着ADR用量的增加,PLA等温结晶速率明显提高,半结晶时间缩短。结合熔体流动速率和偏光显微镜分析,从分子运动能力和熔体黏度的角度解释了ADR对PLA等温结晶行为的影响机理。此外,研究了结晶度变化对PLA/ADR共混物拉伸性能和维卡软化温度(VST)的影响。当PLA/ADR(100/1.0)共混物的结晶度由1.7%提高到32.2%时,其拉伸强度由55.6 MPa提高到63.2 MPa,VST由61.9℃提高到156.9℃。结晶度的增大有利于PLA/ADR共混物力学性能和耐热性能的进一步提高。
Polylactic acid (PLA) was modified by melt chain extension with a multi-component epoxy chain extender (ADR) to obtain PLA / ADR blends. The melt isothermal crystallization behavior of the blends was characterized and analyzed by differential scanning calorimetry (DSC). The results showed that the addition of ADR increased the crystallization rate of PLA melt in the temperature range of 110 ~ 120 ℃. With the increase of the amount of ADR, the isothermal crystallization rate of PLA increased obviously and the crystallization time shortened. Based on the analysis of melt flow rate and polarization microscopy, the mechanism of ADR on isothermal crystallization behavior of PLA was explained from the perspective of molecular mobility and melt viscosity. In addition, the effect of crystallinity on the tensile properties and Vicat softening temperature (VST) of PLA / ADR blends was studied. When the crystallinity of PLA / ADR (100 / 1.0) blend increased from 1.7% to 32.2%, the tensile strength of PLA / ADR blend increased from 55.6 MPa to 63.2 MPa, and the VST increased from 61.9 ℃ to 156.9 ℃. The increase of crystallinity is beneficial to the further improvement of mechanical properties and heat resistance of PLA / ADR blends.