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采用转矩流变仪熔融混合制备了聚丙烯(PP)/碳酸钙(CaCO_3)复合材料,其转矩曲线反映加料、熔融和混合过程及填充增黏效应。DSC、偏光显微镜观察及力学测试表明,CaCO_3纳米粒子界面可诱导PP异相成核并加速结晶,较弱的界面黏结强度和更多更小的PP晶体可吸收更多的能量从而提高冲击强度;但加入过多CaCO_3易发生团聚,延缓结晶,反而降低冲击强度。与这些测试对比,成功用超声波监测变压装置内PP/CaCO_3在很宽温度和压力范围的结晶过程。增加CaCO_3含量会降低声波速度并使相态转变点温度向低温偏移;提高压力会提高相态转变点温度,加快PP结晶和凝固过程。
Polypropylene (PP) / calcium carbonate (CaCO_3) composites were prepared by melt mixing with torque rheometer. The torque curves reflect the process of feeding, melting and mixing and the effect of filling and thickening. DSC, polarized light microscopy and mechanical tests show that CaCO_3 nanoparticles can induce heterogeneous nucleation and accelerate crystallization of PP. The weaker interfacial bond strength and more and smaller PP crystals can absorb more energy to improve the impact strength. But adding too much CaCO_3 prone to reunion, delay crystallization, but reduce the impact strength. In contrast to these tests, the crystallization of PP / CaCO 3 within a wide range of temperature and pressure was successfully monitored by ultrasound. Increasing the content of CaCO_3 will decrease the velocity of acoustic wave and shift the temperature of phase transition point to low temperature. Increasing the pressure will increase the temperature of phase transition point and accelerate the crystallization and solidification of PP.