Studies On The Electrical/Flame-Retardant Propreties Of HDPE Composites

Fire is one of the most common threats to public safety and social development. Static is a usual cause for the burn of polymer materials for charge is easy to accumulated on polymers, thus produce electric sparks. Some fires are also caused by damaged electrical wiring. In that case, we should make sure our materials not only electrically conductive, but also flame retardant. In this paper, electrical conductivity, flame retardant property and mechanical properties of Bromine-Sb2O3flame retardants (BFR) and carbon black (CB)-filled high density polyethylene (HDPE)/ethylene vinyl acetate copolymer (EVA) blends were investigated respectively. The research works are carried out as follows:1. Research of electrical properties of HDPE composites. Ethylene vinyl acetate copolymer (EVA) with9%,18%,28%vinyl acetate (VA) content were blended with HDPE and CB by melt compounding respectively. The effects of EVA content on the electrical and mechanical properties of ternary composites at fixed CB content of6wt%were investigated. Then the effects of CB loading on the electrical and mechanical properties of ternary composites at fixed EVA content of20wt%were investigated. The results show that adding EVA into HDPE/CB composites can improve the electrical properties of the ternary composites. We found out that CB was selective located in HDPE phase through etched experiment and scanning electron microscope (SEM). Adding EVA can improve the toughness of the composites. When15wt%EVA-9, EVA-18and EVA-28were added respectively, the notched impact strength were improved from27.84kJ/m2to41.94kJ/m2>43.66kJ/m2.51.22kJ/m2.2. Research of flame-retardant properties of HDPE composites. Ethylene vinyl acetate copolymer (EVA) with9%,18%,28%vinyl acetate (VA) content and CB were blended with HDPE by melt compounding respectively. The ratio of decabromodiphenyl oxide (DBDPO) and antimony trioxide (Sb2O3) flame retardants and the effects of EVA and CB on the flame-retardant and mechanical properties of ternary composites were investigated. The results show that when the mass ratio of DBDPO and Sb2O3is2.5:1, the composites with10wt%flame retardants can reach V-0level in UL94vertical burning test. We discovered that CB can form char layers and restrain the dripping during combustion of composite. HDPE/15wt%BFR composite with15wt%EVA-9could maitain V-0level in UL94vertical burning test. HDPE/15wt%BFR composite with15wt%EVA-18failed in UL94vertical burning test. HDPE/15wt%BFR composite with15wt%EVA-28could reach V-2level due to the dripping carries heat and molten polymers away. 3. Research of electrical and flame-retardant properties of HDPE composites. EVA with9%,18%,28%VA content, DBDPO, Sb2O3and CB were blended with HDPE by melt compounding. The results show that EVA could improve both electrical conductivity and notched impact strength in an appropriate content. Composite with EVA-9could maintain V-0level in UL94vertical burning test. HDPE/15wt%EVA-18/15wt%(DBDPO/Sb2O3)/6wt%CB composite reaches V-1level in UL94vertical burning test. The charring effect of CB and the existence of EVA result in the fail of HDPE/15wt%EVA-28/15wt%(DBDPO/Sb2O3)/6wt%CB composite in the UL-94test.