Synthesis, morphology and physical properties of multi-walled carbon nanotube/biphenyl liquid crystalline epoxy composites

We have developed multi-walled carbon nanotube/liquid crystalline epoxy composites and studied the effects of incorporation carbon nanotubes (CNTs) on the morphology, thermal and mechanical properties of the composites. The CNTs are functionalized by liquid crystalline (LC) 4,4′-bis(2,3-epoxypropoxy) biphenyl (BP) epoxy resin for the ease of dispersion and the formation of long range ordered structure. The epoxy functionalized CNT (ef-CNT) were dispersed in the LC BP epoxy resin that can be thermal cured with an equivalent of 4,4′-diamino-diphenylsulfone to form composite. The curing process was monitored by polarized optical microscopy. The results indicate the LC resin was aligned along the CNTs to form fiber with dendritic structure initially then further on to obtain micro-sized spherical crystalline along with fibrous crystalline. With homogeneous dispersion and strong interaction between nanotubes and matrix, the composite containing 2.00 wt.% ef-CNT exhibits excellent thermal and mechanical properties. When the amount of ef-CNT exceeds 2.00 wt.%, vitrification stage of curing is fast reached, which lowers the degree of conversion. As compared with the neat resin, the composite containing 2.00 wt.% ef-CNT increases the glass transition temperature by 70.0 °C, the decomposition temperature by 13.8 °C, the storage modulus by 40.9%, and the microhardness by 63.3%.