Electrical Conductivity of High Density Polyethylene/Polyamide 6 Blend Induced by Multi-wall Carbon Nanotubes

One method to improve the electrical conductivity of nanocomposites is the use of immiscible blends containing conductive fillers based on the concept of double percolation. In this research, the electrical and rheological properties of high density polyethylene/polyamide 6 (HDPE/ PA6) blend in presence of multi-wall carbon nanotubes (MWCNTs) were investigated.

Samples based on HDPE/PA6 blend with maleic anhydride-grafted high density polyethylene (HDPE-g-MA) as a compatibilizer and also containing 1, 3 and 5% (by wt) MWCNTs were prepared by melt mixing process in an internal mixer. Then different analyses were performed to investigate the morphology, rheology and electrical properties of samples with different weight percentages of MWCNT and the results were studied.

Scanning electron microscopy (SEM) images of an unfilled blend showed co-continuous morphology and the presence of MWCNTs in the blend also resulted in co-continuous morphology1 and compatibility of the blend with reduced interfacial tension. The rheological properties were characterized using melt rheometric mechanical spectroscopy (RMS). The results showed that with increasing MWCNT content, the storage modulus and complex viscosity of the nanocomposites increased compared to the neat blend and the storage modulus eventually reached a low-frequency plateau region, indicating a rheological percolation threshold of nanocomposite. Storage modulus and loss factor of the blend samples were evaluated using dynamic mechanical analysis (DMA). With increasing MWCNT content, the maximum loss factor of PA6 phase in the nanocomposites decreased with respect to similar phase in the unfilled blend, whereas the maximum loss factor of HDPE phase remained almost constant, indicating a higher presence of MWCNTs in PA6 phase. Also the temperature of the maximum loss factor of the PA6 phase shifted to higher temperatures. The electrical conductivity results according to the four-point probe method showed that the electrical conductivity of the nanocomposite increased significantly by adding 5%  (by wt) MWCNTs.