Mechanical Performance And Interfacial Modification Of Long Basalt Fiber Reinforced Thermal Plastics Composites

As basalt fiber has great advantage over glass fiber in terms of thermo stability and corrosion resistance, and shows better cost performance than carbon fiber, it is a new kind of base material and hi-tech fiber that appealing to industry development need. Combined with mechanism of interfacial action, studying basalt fiber and reinforcing thermoplastics composites'properties will represent great significance in the field of researches in using fiber to reinforce thermoplastics composites.This article will conduct a comparison between basalt fiber and glass fiber in thermo stability and corrosion resistance, and therefore defines its remarkable advantage in extreme conditions. Basalt fiber has stable water tolerance, acid resistance, alkali resistance in normal temperature and stable mechanical properties at the temperature of300℃. In high temperature caustic treating, its mechanical properties perform as a process of increasing after decreasing and finally decreasing, but the total properties are better than those in glass fiber. Consequently, it has considerable value to do some research in trying to apply basalt fiber into reinforcing thermoplastics composites instead of the conventional one-glass fiber.The condition of cementation between fiber and matrix interface has great influence on long fiber reinforcing thermoplastics composites'combination properties. This article brings macromolecular coupling agent to analyze interfacial effect systematically.In the research, auto transfer radical polymerization (ATRP) is used to compound block copolymer, which is called polystyrene-b-poly-2-Hydroxyethyl acryl ate (PS-b-PHEA). In this block copolymer, PS blocks have a remarkable compatibility with matrix, and are able to bring about high degree mutual diffusion and tangles with matrix molecular chain, therefore forms strong interface bonding with matrix. On one hand, PHEA has several hydroxyls, whose active hydroxyls can react with Si-OH on the surface of basalt fiber and form stable chemical bond; on the other hand, because of low transforming temperature in glassification (Tg), PHEA blocks can be used as flexible segment, which will form flexible layer on the interface, relax the thermal stress there, scatter external load immediately and take in the energy from external force; Moreover, extra hydroxyls may bring in new functional group, therefore we introduce light-sensitive material, with which we can control the interfacial structure through light cross linking degree. Modified with block copolymer, copolymer brush may be formed on the surface of basalt fiber, decreasing its surface energy and increasing its compatibility with matrix. Through micro-deboned test, we can see that interface of composite reaches its corresponding maximum shear strength when the mass concentration of molecular-structured block copolymer solution is5.00%and the reaction time is24h. Also, result of this test shows that shear strength on interface of block copolymer increase with the length of polystyrene block chain, until it reach a fixed value. Meanwhile, with certain amount of PS, shear strength on interface of block copolymer reach its peak value when the length of PHEA chain is120. Moreover, after light-sensitive material is introduced, it is easier to handle interfacial layer control. According the data of micro-deboned test, brought in light-sensitive groups, block copolymer with long flexible PHEA segment has higher Tg, thus enhances bonding on the interface. Composites have their strongest interfacial acting force when acryl chloride group has a grafting degree of50%, and the illumination time reaches2h.Interfacial crystallization behaviors were studied with a microscope under the condition of static crystallization in BF/PP composites. When the interfacial adhesion between fiber and matrix is strong enough, the transcrystalline can be formed under isothermal crystallization or slow cooling down. To evaluate the transcrystalline behaviors caused isothermal crystallization was performed in a PP/MPP system. Big gap is found when the interfacial adhesion is strong, and a new interface can be formed. The gap disappears when the fiber was treated by the coupling agent PS-b-PHEA as the segment of PHEA is240. In this situation, the flexible interlayer formed by the flexible block PHEA of PS-b-PHEA could relax some part of thermal stress resulted from interface temperature gradient arising from sample cooling for crystallization.The effect of transcrystallization and the influence of thermal treatment on interfacial bond strength of BF/PP system was studied by means of the Microbond Test. Results demonstrate that the interfacial shear strength decreased when the transcrystalline was formed, which is because of the decreasing contraction force acting on the interphase. Thus the rupture of the transcrystalline sample occurs in the polypropylene matrix. The interfacial shear strength of the transcrystalline sample increased after thermal treatment. It is due to the relaxation of the thermal stress in the interfaces and the perfectness of crystallites after thermal treatment.Wet impregnated process and direct extruded process are adopted in producing long basalt fiber to reinforce thermoplastics composites and studying the impact of process technique, the process technology, the amount of fiber and the separation conditions upon LFT's properties. The mechanical properties improvements of introducing the macromolecular coupling agent as the interface layer are researched under the same process condition. The mechanical properties increased with increasing the length of PS segment eventually tend to balance, and it will appear a maxium number during the flexible segment PHEA increasing.Through this research, direct extruded process has better separation effect and comparatively shows greater mechanical properties than wet impregnated process, because of its strong shear effect. In both technique conditions, LFT's mechanical properties will reach its optimal value when the amount of MPP is8%and the amount of fiber is40%.In this article, the composites machenical property can be improved and expand its application field by the interfacial improvement. It is of great significance for control the composites property and achieving sustainable development.