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通过快速增压法(RC)和自然冷却法(CN)分别制备出完全非晶的聚乳酸(PLA)样品,利用差示扫描量热仪(DSC)、偏光显微红外光谱仪(FTIR)和广角X-ray(WAXD)研究了2种非晶样品的初始结构、不同结晶温度下的等温冷结晶行为及最终的微观结构.结果表明,在温度为110、115、125、130、135及140℃下等温结晶时,RC样品的结晶速率明显高于CN样品;WAXD数据显示,结晶完成后RC样品的结晶度明显高于CN样品,但两者最终的晶粒尺寸大小相近,说明RC样品结晶过程中具有较高的成核密度;实验发现,PLA熔体在快速增压过程中很可能形成了某些类似物理老化样品中存在的局部有序结构,这些局部有序结构促进了晶核的形成,使冷结晶速率明显加快,结晶度提高.
A completely amorphous sample of polylactic acid (PLA) was prepared by rapid pressurization (RC) and natural cooling (CN), respectively. The samples were characterized by differential scanning calorimetry (DSC), polarized microscopy (FTIR) The initial structure, the isothermal cold crystallization behavior and the final microstructure of two kinds of amorphous samples were studied by X-ray (WAXD) .The results showed that at the temperatures of 110, 115, 125, 130, 135 and 140 ℃ In the case of isothermal crystallization, the crystallization rate of RC samples was significantly higher than that of CN samples. The WAXD data showed that the crystallinity of RC samples after crystallization was significantly higher than that of CN samples, but the final crystal sizes were similar, indicating the crystallization process of RC samples . The experimental results show that PLA melts are likely to form locally ordered structures in some similar physically aged samples during rapid pressurization. These locally ordered structures promote the formation of nuclei , So that the crystallization rate was significantly accelerated, increased crystallinity.