Morphological, electrical and mechanical properties of ultrahigh molecular weight polyethylene and multi-wall carbon nanotube composites prepared in decalin and paraffin

Ultrahigh molecular weight polyethylene (UHMWPE) and multi-wall carbon nanotube (MWNT) composites were prepared using either decalin or paraffin as solvent. Electrical conductivity measurements were performed for the original and heat-treated composites. The drastic increase in conductivity occurred at low MWNT content for the composite prepared in paraffin, while the conductivity of the composite prepared in decalin increased slightly up to 10 wt % MWNT content. Scanning electron microscopy observations revealed that the MWNTs within the composite prepared in decalin were covered by UHMWPE, and their average diameters were much greater than those of the original MWNTs, while the average diameter of the MWNTs within the composite prepared in paraffin was similar to the diameter of the original MWNTs. Such different morphology was found to be due to the different crystallization. The composites prepared in decalin had high drawability. Interestingly, the conductivities of the drawn (up to 50 times) and undrawn UHMWPE-MWNT composites were almost equal, independent of the MWNT content. As for the UHMWPE-MWNT composite (drawn up to 50 times) with 15 wt % MWNT content, the conductivity reached up to 10(-1) S/cm, and the modulus was higher than 50 GPa at ca. 25 degrees C, indicating that a polymeric material with high modulus and relative high conductivity was successfully prepared.