Study On Modified Ca-Bentonite Collaborated With Halogen-Antimony Flame Retardants Flame Retardant High Density Polyethylene

High density polyethylene (HDPE) is a kind of high crystallinity, non-polar thermoplastic resin. It is widely used in cables, pipes, automotive manufacturing field because of its abundant source, good performance. But HDPE is a highly flammable material, produces heavy smoke and serious melt dripping during burning, which has a potential risk of fire. Therefore, in order to reduce fire hazard and broaden the application scope of the HDPE, the research of HDPE flame retardant, suppression of smoke and melt dripping has great significant.In this paper, alkaline Ca-bentonite and organically modified Ca-bentonite collaborate with halogen-antimony flame retardants to flame retardant high density polyethylene (HDPE) was studied. The flame-retardant synergism of the several kinds of flame retardants and halogen-antimony flame retardant was studied by the tests of oxygen index, horizontal vertical combustion level, tensile strength, bending strength, impact strength and heat weightlessness. The main research contents and conclusions were as follows:The flame retardant property, mechanical property and thermostability of the HDPE composites were all good, when halogen-antimony flame retardants was used alone in HDPE and the dosage of DBDPE and Sb2O3 was 18 and 6 wt.% respectively. But the costs was high, the amount of smoke and melt dripping phenomenon was serious. On this basis, the alkaline Ca-bentonite was also added in the HDPE composites. And the influence of the dosage and anion exchange capacity of alkaline Ca-bentonite on the properties of the HDPE composites was investigated. The results showed that, the oxygen index of the composites increased with the increase of the dosage of alkaline Ca-bentonite, when the dosage of alkaline Ca-bentonite was 4 wt.%, the oxygen index of the HDPE composites was the highest of 32.51%, which was 4.41% higher than that of halogen-antimony flame retardants was used alone in HDPE. In the meantime, the HDPE composites also have better mechanical property and thermostability and the amount of smoke when burning was reduced and melt dripping phenomenon was improved. The increase of the anion exchange capacity of alkaline Ca-bentonite could lead to the reduce of the flame retardant property, comprehensively considering the flame retardant properties, mechanical property, thermostability, and much morse amount of smoke when burning and melt dripping phenomenon, the best anion exchange capacity of alkaline Ca-bentonite was 1.5.The influence of the dosage of silane coupling agent modified Ca-bentonite on the properties of the halogen-antimony flame-retardant HDPE composites was investigated. Even though the addition of silane coupling agent modified Ca-bentonite leaded to the oxygen index with a small decline, the mechanical property and thermostability had greatly improved, and the amount of smoke when burning and melt dripping phenomenon would be better. When the dosage of silane coupling agent modified Ca-bentonite was 4 wt.%, the HDPE composites had the best integrated performance with a high oxygen index of 27.3%.Under the condition of the total amount of the flame retardant materials remained unchanged. Using silane coupling agent modified Ca-bentonite partly replace the antimony trioxide could reduce the consumption of halogen-antimony flame retardants. Not only got the cost savings, but also could keep the HDPE composites had a good flame retardant property with a high oxygen index of 27.21%. What’s more, the effect of suppression of smoke and molten drop was significant, and the mechanical property and thermostability was greatly improved.At last, the influence of the four kinds of modified bentonite (alkaline Ca-bentonite, silane coupling agent modified Ca-bentonite, cetyl trimethyl ammonium bromide modified Ca-bentonite and stearic acid modified Ca-bentonite) on the properties of the halogen-antimony flame-retardant HDPE composites were compared. The results showed that alkaline Ca-bentonite had the best synergistic flame retardant performance with the highest oxygen index and lowest weight loss ratio.