Preparation bv melt mixing and characterization of isotactic polypropylene/SiO2 nanocomposites containing untreated and surface-treated nanoparticles
Preparation bv melt mixing and characterization of isotactic polypropylene/SiO2 nanocomposites containing untreated and surface-treated nanoparticles
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DOI：
10.1002/app.22849
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发表时间：
2006-05-15
影响因子：
3
通讯作者：
Karayannidis, GP
中科院分区：
文献类型：
--
作者：
Bikiaris, DN;Papageorgiou, GZ;Karayannidis, GP
在本研究中，两个系列的全同立构聚丙烯（iPP）/SiO2纳米复合材料含有1，2.5，5，7.5，和10重量%的SiO2纳米粒子通过熔融混合在一个双螺杆同向旋转挤出机。在第一系列中，使用未处理的气相二氧化硅纳米颗粒，而在第二系列中，用二甲基二氯硅烷进行表面处理。在这两种情况下，初级纳米颗粒的平均尺寸为12 nm。拉伸强度和冲击强度增加，主要是由二氧化硅纳米粒子的类型和含量的影响。观察到最大值，对应于含有2.5wt%SiO2的样品。这些结果进行了讨论，在光的SEM和TEM观察。通过增加纳米颗粒的量，可以形成气相二氧化硅的大聚集体，这可以解释较高浓度的SiO2的机械性能的降低。然而，据发现，表面处理的纳米粒子产生更大的聚集体比那些来自未经处理的纳米粒子，尽管增加的粘附性的iPP矩阵，从屈服强度假设。这种行为对机械性能产生负面影响。此外，努力确定增韧理论，主要是橡胶增韧或复合材料的临界颗粒间距离，也可能适用于纳米复合材料。DSC测试结果表明，二氧化硅纳米粒子作为有效的成核剂，提高了iPP的结晶速率和结晶度。(c)2006 Wiley Periodicals，Inc.
In the present study two series of isotactic polypropylene (iPP)/SiO2 nanocomposites containing 1, 2.5, 5, 7.5, and 10 wt % SiO2 nanoparticles were prepared by melt-mixing on a twin-screw corotating extruder. In the first series untreated fumed silica nanoparticles were used, whereas in the second nanoparticles were surface-treated with dimethyldichlorosilane. hi both cases, the average size of the primary nanoparticles was 12 nm. Tensile and impact strength were found to increase and to be affected mainly by the type and content of silica nanoparticles. A maximum was observed, corresponding to samples containing 2.5 wt % SiO2. These findings are discussed in light of the SEM and TEM observations. By increasing the amount of nanoparticles, large aggregates Of fumed silica could be formed, which may explain the reduction of mechanical properties with higher concentrations of SiO2. However, it was found that surface-treated nanoparticles produced larger aggregates than did those derived from untreated nanoparticles, despite the increased adhesion of the iPP matrix, as was postulated from yield strength. This behavior negatively affected mechanical properties. In addition, an effort was made to determine if toughening theories, mainly the critical interparticle distance for rubber toughening or composites, also might be applicable in nanocomposites. From DSC measurements it was demonstrated that silica nanoparticles acted as effective nucleating agents, increasing the crystallization rate and the degree of crystallinity of iPP. (c) 2006 Wiley Periodicals, Inc.