导热绝缘复合材料的制备和研究

发布时间：2018-01-20 18:10

本文关键词： 词:PBT PP SiC GF 热性能　出处：《苏州大学》2015年硕士论文　论文类型：学位论文

【摘要】：近年来,聚合物基导热绝缘复合材料在散热领域发挥着越来越重要的作用,因为散热问题会直接影响元器件的稳定性和使用寿命。相比于传统导热材料(金属、陶瓷),聚合物基导热复合材料具有质量轻和易于加工设计的优点。但是,纯聚合物的导热系数非常低,通常在0.1-0.5 W/m K范围内,因此常使用导热填料填充聚合物以克服聚合物的低导热性缺点。本文中,首先采用玻纤增强PBT(PBT-20%GF)和不同含量的Si C通过熔融共混得到PBT/Si C复合材料。当Si C填料的含量达到50 wt%时,PBT/Si C复合材料的导热系数仅为0.6145 W/m K,且在较高填充量时,由于超细Si C颗粒比表面积大,颗粒间容易团聚,这会导致复合材料的加工性能变差。加入适量的偶联剂KH550可以在一定程度上改善PBT/Si C复合材料的导热系数,但提高幅度非常有限。为了进一步提高复合材料的导热性能和改善加工性能,在该导热复合材料中引入第二相聚合物PP,使用玻纤增强PBT(PBT-20%GF),通过二步加工法制备PBT/PP/Si C复合材料,使填料分散在PBT相中,通过形成较理想的导热填料分布,提高了填料在PBT相中的有效浓度,继而进一步提高了其导热系数。研究了填料含量对复合材料PBT/PP/Si C的流变性能、微观结构、热性能、力学性能和介电性能的影响。实验结果表明,PP形成分散相,PBT形成连续相,而Si C选择性地分布在PBT相中。PBT/PP/Si C复合材料的导热系数随着碳化硅含量的增加而增加,当碳化硅的填充量达到40 wt%时,导热系数为1.181 W/m K,是PBT/PP复合材料的近四倍。在相同的填充含量时,PBT/PP/Si C复合材料的导热系数比PBT/Si C复合材料的导热系数高。由此可见,第二相聚合物PP具有尺寸占据效应以此提高了填料的有效浓度,PBT/PP/Si C复合材料的导热系数随之升高。另外,玻璃纤维材料具有较大的长径比,能有效地互相接触而形成导热网络,玻璃纤维与超细颗粒复合填充聚合物不仅能增大玻璃纤维与基体树脂的接触面积,还能有效地促进颗粒的定向分布从而提高复合材料的导热性能。因此本文还通过静电复合技术在玻璃纤维表面包覆超细碳化硅颗粒,然后通过熔融共混法制备了PBT/GF-Si C复合材料,分别研究了填料含量对PBT/GF-Si C复合材料的微观构、热性能、动态力学性能和介电性能的影响。实验结果表明,经过剪切作用之后,部分碳化硅颗粒仍包覆在玻璃纤维表面并且相互接触,其它颗粒则从玻璃纤维表面脱落下来,但仍分散在玻璃纤维周围形成有效堆砌,在局部范围内增大填料浓度,从而形成有效的导热通路。当GF-Si C的含量为30 wt%时,PBT/GF-Si C复合材料的导热系数为0.6392 W/m K,约为PBT/GF/Si C复合材料的近两倍,这也说明对玻璃纤维表面预处理是有效果的。
[Abstract]:In recent years, polymer based thermal insulation composites play a more and more important role in the field of heat dissipation, because heat dissipation directly affects the stability and service life of components, compared with traditional thermal conductive materials (metals). Ceramic, polymer-based thermal conductivity composites have the advantages of light weight and easy to design. However, the thermal conductivity of pure polymers is very low, usually in the range of 0.1-0.5 W / m K. Therefore, thermal conductive fillers are often used to fill polymers to overcome the shortcomings of low thermal conductivity of polymers. First, glass fiber reinforced PBTT-20 is used. PBT/Si C composites were obtained by melt blending with different contents of sic, when the content of sic filler reached 50 wt%. The thermal conductivity of PBT/Si C composites is only 0.6145 W / m K, and the superfine sic particles are easy to agglomerate because of the large specific surface area of the superfine sic particles. The thermal conductivity of PBT/Si C composites can be improved to some extent by adding appropriate coupling agent KH550. In order to further improve the thermal conductivity and processability of the composites, the second phase polymer PP was introduced into the composites. The PBT/PP/Si C composites were prepared by using glass fiber reinforced PBT-20 / GFN method. The fillers were dispersed in the PBT phase. The effective concentration of filler in PBT phase was increased by forming an ideal distribution of thermal conductive filler. The rheological properties, microstructure and thermal properties of PBT/PP/Si C composites were studied. The influence of mechanical properties and dielectric properties. The experimental results show that PP forms dispersed phase and PBT forms continuous phase. However, the thermal conductivity of sic / PP / sic composites increased with the increase of sic content when the content of sic reached 40 wt%. The thermal conductivity is 1.181 W / m K, which is nearly four times of that of PBT/PP composites. The thermal conductivity of PBT/PP/Si C composites is higher than that of PBT/Si C composites. The second phase polymer PP has the size occupation effect to increase the effective concentration of filler and the thermal conductivity of PBT / PP / Si C composites. Glass fiber material has a large aspect ratio and can effectively contact with each other to form a thermal network. The composite polymer filled with glass fiber and ultrafine particles can not only increase the contact area between glass fiber and matrix resin. It can also effectively promote the directional distribution of particles and improve the thermal conductivity of composites. Therefore, this paper also coating ultrafine silicon carbide particles on glass fiber surface by electrostatic composite technology. Then, PBT/GF-Si C composites were prepared by melt blending method. The microstructure and thermal properties of PBT/GF-Si C composites with filler content were studied. The effect of dynamic mechanical properties and dielectric properties. The experimental results show that after shear, some sic particles are still coated on the surface of glass fiber and contact with each other. Other particles fell off the surface of the glass fiber, but still dispersed around the glass fiber to form an effective pile up, increasing the concentration of filler in the local range. When the content of GF-Si C is 30 wt%, the thermal conductivity of PBT / GF-Si C composite is 0.6392 W / m K. It is about twice as much as PBT/GF/Si C composite material, which also shows that the pretreatment of glass fiber surface is effective.
【学位授予单位】：苏州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB332

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