Study On Temperature-resistance Properties Of WC/HDPE Conductive Composites

In this study,Tungsten carbide/High density polyethylene(WC/HDPE)conductive composites were prepared by melt blending with WC as conductive filler and HDPE as polymer matrix,and the electrical conductivity,morphology,rheological behavior and mechanical properties of the composites were investigated.At 25 oC,when the WC content of WC/HDPE conductive composite is 20~30 vol%,the composite exhibits obvious percolation transition behavior,and the volume resistivity decreases by 12 orders of magnitude.With the increase in conductive filler,the intensity of Iptc increases gradually,and the resistivity of room temperature decreases gradually.The distribution of conductive filler gradually changes from loose to dense.When the content exceeds 40 vol%,agglomeration occurs.The torque of the composites is gradually increased and the plasticizing time increased during processing.The dynamic rheological analysis demonstrates that the storage modulus(G’)and complex viscosity(η*)increase with the increase in filler content,and the G’ and tan δ increase with the increase in shear frequency.When the WC content is 30~35 vol%,the jumps appear,indicates that the conductive network within the system is gradually forming.And the elongation at break of the material gradually decreases,the elastic modulus increases gradually,the tensile strength initially increases and subsequently decreases,and the impact strength decreases gradually.The WC/HDPE conductive composites were modified by adding cross-linking agent and isothermal heat treatment.The positive temperature coefficient(PTC)repeating stability,intensity of PTC(Iptc)strength and other related properties of the modified composites were studied.The WC/HDPE(30/70)conductive composite was modified by using dicumyl peroxide(DCP)and Triallyl isocyanurate(TAIC).Studies demonstrates that as the DCP content increases,the torque of the composite increases first and then decreases.When the crosslinker content is 1.0wt%,the maximum torque is 3.27 kgf·cm.At the same time,with the increase of DCP,the gel content and crosslink density of the composites gradually increase,and at 25 oC,the resistivity initially decreases and subsequently increases.When the DCP content is 1.0wt%,the Iptc intensity repeat stability is preferably 6.6.SEM and XRD results show that when the DCP content is 1.0wt%,the dispersibility of the filler is good,and the material can still maintain the original crystal structure.The WC/HDPE(30/70)conductive composites were subjected to isothermal heat treatment.Studies demonstrates that as the isothermal heat treatment temperature and time increase,at 25 oC,the resistivity of the composite initially decreases and subsequently increases,and the Iptc intensity initially increases and subsequently decreases.When the composite was heat treated at 110 oC for 12 h,the PTC repeat stability of the material was better,Iptc maintained at 7.1,and the initial resistivity at 25 oC was maintained at 240 ?·cm.