Yang Biao, Zhang Xin, Wang Chun, Liu Ran, Fan Baomin, Zhang Huijuan, Sun Hui
School of Materials Science and Mechanical Engineering, Beijing Technology and Business University Beijing 100048 P. R. China
RSC Adv. 2019 Nov 12;9(63):36815-36824. doi: 10.1039/c9ra08133j. eCollection 2019 Nov 11.
Polyvinyl acetaldehyde (PVAC) and polyvinyl butyral (PVB), as nucleating agents, were melt mixed with poly(ε-caprolactone) (PCL), and the non-isothermal crystallization behavior and crystalline morphology of PCL was characterized using differential scanning calorimetry (DSC) and polarizing microscopy (POM). It was found that melt shearing made the crystallinity of control PCL increase from 37.94% (as-received) to 41.15% and the crystallization temperature raised by 7.7 °C. As the mass fraction of polyvinyl acetals increased from 0.1 wt% to 10 wt%, both crystallization temperature and crystallinity of PCL were decreased; the spherulite size of PCL was increased from a few microns to 200 μm and a fast cooling procedure facilitated the homogeneity of spherulite size. When the content of nucleating agent was less than 1 wt%, no obvious microphase separation was observed under scanning electron microscopy; the tensile strength, yield strength and elongation at break of PCL increased slightly; and the Young's modulus of PCL was improved by 67% at a 0.1 wt% mass fraction of PVB which is beneficial to PCL in high load bearing applications. When the contents of nucleating agents were higher than 1 wt%, the microphase separation occurred obviously and a large amount of fine spherulites appeared with the deterioration of mechanical properties. The modified Avrami and Tobin models could well describe the non-isothermal crystallization kinetics.
将聚乙烯醇缩乙醛（PVAC）和聚乙烯醇缩丁醛（PVB）作为成核剂与聚（ε-己内酯）（PCL）进行熔融共混，并采用差示扫描量热法（DSC）和偏光显微镜（POM）对PCL的非等温结晶行为和结晶形态进行了表征。结果发现，熔体剪切使对照PCL的结晶度从37.94%（原样）提高到41.15%，结晶温度升高了7.7℃。随着聚乙烯醇缩醛质量分数从0.1 wt%增加到10 wt%，PCL的结晶温度和结晶度均降低；PCL的球晶尺寸从几微米增加到200μm，快速冷却过程有利于球晶尺寸的均匀性。当成核剂含量小于1 wt%时，扫描电子显微镜下未观察到明显的微相分离；PCL的拉伸强度、屈服强度和断裂伸长率略有增加；在PVB质量分数为0.1 wt%时，PCL的杨氏模量提高了67%，这有利于PCL在高承载应用中使用。当成核剂含量高于1 wt%时，明显发生微相分离，出现大量细小的球晶，力学性能恶化。修正的Avrami模型和Tobin模型能够很好地描述非等温结晶动力学。
