压缩和回复下PA6/MWCNTs/SSFs复合材料导电性研究

Electrical Conductivity of PA6/MWCNTs/SSFs Composites under Compression and Recovery

通过熔融共混、注射成型将多壁碳纳米管(MWCNTs)和不锈钢纤维(SSFs)与尼龙(PA)6复合制成PA6/MWCNTs/SSFs导电复合材料,在万能试验机上对其进行单轴压缩蠕变和阶梯回复实验,对材料的电阻率、应力、应变进行同步测量,研究不同应力及SSFs含量下复合材料的电阻率变化。结果表明,该复合材料在阶梯应力加载瞬间发生普弹形变,维持恒定应力后,发生高弹形变和粘流形变,阶梯应力卸载后,应变会有所回复。压缩蠕变状态下,当应力为10,20 MPa时,加载瞬间复合材料电阻率会发生突变下降;当应力维持在10 MPa时,电阻率随应变的增加呈下降趋势,即发生电阻蠕变现象,SSFs质量分数为10%的复合材料电阻蠕变现象最为明显;随着应力水平增大,电阻蠕变现象消失,电阻率趋于稳定,但当SSFs质量分数为8%时,电阻率存在较大波动;阶梯回复状态下,复合材料电阻率基本稳定,但当应力卸载到10 MPa时,电阻率存在波动,随着SSFs含量增加,波动趋于平缓。根据Burgers蠕变模型以及聚合物荷载响应特点,认为这主要是由于聚合物分子链的运动对导电通路的影响引起的。

PA6 /multi-wall carbon nano-tubes （MWCNTs）/stainless steel fibers （SSFs） conductive composites were prepared by melt-blending and injection molding. Compressive creep and step recovery experiments of the conductive composites were done by universal testing machine. The resistivity, stress and strain of the composites were measured synchronously in the process of experiments and the resistivity changes of the composites with different SSFs contents under different stress were studied. The results show that the composites exist regular elastic deformation at the instantaneous step stress and high elastic deformation together with viscosity flow deformation at the constant stress, morever, the strain recovers slightly when the step stress is. unloaded. Under compressive creep condition, the resistivity of the composites drop quickly when the instantaneous stress is 10 MPa or 20 MPa , it decreases with the increase of strain when the contast stress is 10 MPa, this phenomenon is known as resistance creep, which is the most obvious when the mass fraction of SSFs is 10%. The resistance creep disappears with the growth of the stress, as a result, the resistivity tends to reach steady states but fluctuates obviously when the mass fraction of SSFs is 8%. The resistivity is basically stable during step recovery but fluctuates when the stress is unloaded to 10 MPa, however, the fluctuation is weakened with the increase of SSFs content. According to Burgers creep model and loading response of polymer composites, it is believed that the fluctuation of resistivity is mainly affected by the change of conductive network due to the motion of polymer molecular chain.