Preparation And Characterization Of Low-Smoke Halogen-Free Flame Retardant Polyolefin Composites

Polyolefin is widely used in many fields such as cable and wire, chemistry and electrical and electronics industry, etc. However, its extensive application was restricted because of its low LOI, flammability and dropping when burning. At present, the main flame-retardant systems for polyolefin are based on halogen, Mg(OH) 2 and Al(OH)3. For halogenated flame retardants, there are potential damaging effects on environment. Mechanical properties of materials were affected seriously because the addition of Mg(OH)2 and Al(OH)3 were too large.This paper studied on the effect of contents of layered double hydroxides (LDHs) on the mechanical, combustion and rheological properties of linear low density polyethylene (LLDPE) composites filled with LDHs. The results showed that LLDPE/LDHs composites had fire retardant properties when a lot of LDHs was filled. The effects of synergistic flame retardants of micro-capsules of red phosphorus (MRP), expandable graphite (EG), and ammonium polyphosphate (APP), antimony trioxide (Sb2O3) and Ferrocene (FC) were studied further. It was found that MRP, Sb2O3 and FC had best synergistic action to LDHs. The optimal flame retardant formula was screened out.The surface of LDHs was modified by titanates coupling agent NDZ-201, silane coupling agent KH-570, stearic acid and stearic acid-rare earth coupling agent. The results showed that the functional groups of LDHs were changed and the layer structure of LDHs kept invariant after modified by every coupling agent. After the LDHs was modified, the Elongation at break and rheological properties of LLDPE/LDHs composites improved.The tensile ratio of the system has been improved through increasing the content of EVA, decreasing the content of LDHs and filled with DCP properly. Eventually, LLDPE/LDHs composites with outstanding flame retardant ability, hot-endurance ability, mechanical properties and electrical properties were prepared.