Toughening of polypropylene with calcium carbonate particles
Toughening of polypropylene with calcium carbonate particles
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DOI：
10.1016/s0032-3861(02)00769-3
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发表时间：
2001
期刊：
影响因子：
4.6
通讯作者：
W.C.J. Zuiderduin;C. Westzaan;H. Huetink;R. J. Gaymans
中科院分区：
文献类型：
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作者：
W.C.J. Zuiderduin;C. Westzaan;H. Huetink;R. J. Gaymans
在双螺杆挤出机上制备了颗粒含量为0-32vol%的PP-CaCO3复合材料。研究了粒子粒径(0.07~1.9μm)和粒子表面处理(添加硬脂酸和不添加硬脂酸)对增韧性能的影响。聚丙烯的基质相对分子质量也不同(MFI为0.3-24dg/min)。实验包括拉伸实验、缺口冲击实验、差示扫描量热仪(DSC)、扫描电子显微镜和流变学实验。复合材料的弹性模量随填料含量的增加而增大，屈服应力随填料含量的增加而降低。这种屈服应力的降低与颗粒从聚丙烯基质中脱粘有关。DSC实验表明，粒子含量对PP的熔融温度和结晶度没有影响，粒子大小对PP的热性能也没有影响。随着粒子含量的增加，材料的抗冲击性能有较大提高。加入CaCO3颗粒后，脆韧转变温度从90℃降至40℃。缺口Izod断裂能从2提高到40-50kJ/m2。粒子表面的硬脂酸涂层对冲击强度有较大的正向影响。这主要是由于碳酸钙颗粒分散性的提高。颗粒的聚集显然对复合材料的冲击行为有不利影响。较小的粒子尺寸(<；0.7μm)表现出较粗糙的形态，这降低了增韧效率。聚丙烯基质的相对分子质量对其增韧性能有很大影响。较高的分子质量使脆性到韧性的转变向较低的温度移动。然而，在较高的填充量(>；20Vol%)下，分散性似乎仍然出现问题，从而降低了增韧效率。在本研究中使用的所有颗粒类型中，硬脂酸处理的颗粒为0.7μm的颗粒具有最佳的性能组合。从微观增韧机理的研究表明，在低应变下，粒子仍然附着在基质聚合物上。在较高应变下，颗粒脱粘，这导致颗粒尺寸水平上的应力状态发生变化。这可以防止基质聚合物的银纹，并允许广泛的塑性变形，从而产生大量的断裂能。
Polypropylene–CaCO3composites were prepared on a twin screw extruder with a particle content of 0–32vol%. The influence of particle size (0.07–1.9μm) and surface treatment of the particles (with and without stearic acid) on the toughening properties were studied. The matrix molecular weight of the polypropylene was also varied (MFI 0.3–24dg/min). The experiments included tensile tests, notched Izod impact tests, differential scanning calorimetry (DSC), scanning electron microscopy and rheology experiments. The modulus of the composites increased, while the yield stress was lowered with filler content. This lowering of yield stress was connected to the debonding of the particles from the polypropylene matrix. From DSC experiments it was shown that the particle content had no influence on the melting temperature or crystallinity of the PP phase, also particle size showed no effect on the thermal properties. The impact resistance showed large improvement with particle content. The brittle-to-ductile transition was lowered from 90 to 40°C with the addition of CaCO3particles. Notched Izod fracture energy was increased from 2 up to 40–50kJ/m2. The stearic acid coating on the particle surface showed a large positive effect on the impact strength. This was mainly due to the improved dispersion of the CaCO3particles. Aggregates of particles clearly had a detrimental effect on the impact behaviour of the composites. The smaller particle sizes (<0.7μm) showed coarse morphologies and this lowered the toughening efficiency. The molecular weight of the polypropylene matrix had a profound effect on the toughening properties. A higher molecular mass shifted the brittle-to-ductile transition towards lower temperatures. At the higher filler loads (>20vol%), however, still problems seem to occur with dispersion, lowering the toughening efficiency. Of all particle types used in this study the stearic acid treated particles of 0.7μm were found to give the best combination of properties. From the study of the micro-toughening mechanism it was shown that at low strain the particles remain attached to the matrix polymer. At higher strain the particles debond and this leads to a change in stress state at the particle size level. This prevents crazing of the matrix polymer and allows extensive plastic deformation, resulting in large quantities of fracture energy.