Study On Cell Structure Control Technology Of Microcellular Polypropylene Composites

When the microcellular polymer material is used as structural materials, its strength and toughness need to be further improved.Currently, fiber is mainly used for reinforcement, scholars have done a lot of research from the perspective of interface behavior and modification mechanism.For the reinforced foaming materials, the optimization of thefoam quality is the key scientific issue to be addressed.On the one hand, improving the foaming quality can inhibit the aggregation of vapor at the surface of the reinforcement phase;on the other hand, the small and uniform cell structure is favor to enhance its strength and toughness.Thus, for the reinforced foaming polymer materials, the regulation of foaming quality has very important significance for the industrial application of foam products.This paper selects three typical fibers(AF, GF, CF). The influence of fiber properties and fiber surface modification on the foaming behavior of micro-foamed polypropylene composite materials.Effects of the processing technology, composite foaming agent on the regulation mechanism of the cell structure are investigated.The main work and results presented in this thesis are as follows:1.The short fiber can effectively improve the cell structure of foamed PP material,and CF>GF>AF.The cell diameter of PP/CF foams is 27.689μm.The cell density of PP/CF foams is 8.67×106cells/cm3.The cell diameter and density of unmodified GF foams are respectively 29.67μm, 3.45×107cells/cm3, and 42.56μm, 8.39×106cells/cm3 for modified GF foams.The proportion of the isolated type of cell-GF increased.2.From the foaming process visualization we can find that the longer the cell growth, the more serious cell coalescence. Higher mold temperature results in a larger cell diameter and a smaller cell density due to the longer cell growth time. Compared with pure PP foams, the appearance of the over foaming state for PP/GF foams was delayed.3.With the increase of the core-pulling rate, the cell diameter reduces from26.678μm to 17.998μm, the cell density increases from 1.41×107cell/cm3 to 4.66×107cell/cm3.4.The wet grinding method is not suitable for the preparation of AC/diatomite composite foaming agent. The diatomite/OBSH composite foaming agent were prepared by solution method with the good dispersion of OBSH foaming agent.Compared with the OBSH foaming agent, diatomite/OBSH composite foaming agents make the cell diameter decrease from 275.47μm to 176.45μm and the cell density increase from 3.32×103cells/cm3 to 5.73×104cells/cm3.