The Effect Of Modified Expandable Graphite On The Flame Retardancy And Smoke Suppression Of ABS Composites

Acrylonitrile-butadiene-styrene terpolymer(ABS)is widely used in electronic appliances,automobiles,production and life,but ABS is highly flammable and produces a lot of black smoke and molten droplets during combustion,which is harmful to the life and properties safety.Therefore,it is of theoretical and practical significance to conduct halogen-free flame retardant and smoke suppression research on ABS.In this work,we try to design a halogen-free flame retardant system to reduce the flame retardant loading and smoke release of flame retardant ABS composites.Expandable graphite(EG),phytate-coated expandable graphite(PA-EG),and silicon-boron resin-coated expandable graphite(B-Si-EG)were prepared.The above mentioned three kinds of EG were melting blended with ABS in a compactor with halloysite nanotubes(HNTs),ammonium polyphosphate(APP),and 9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide(DOPO),respectively.The ABS composites were prepared,and the flame retardancy,smoke suppression and mechanical properties of the composites were investigated.The main research works are as follows:(1)EG,HNT and APP were melting blended with ABS.It was found that the limiting oxygen index(LOI)of the ABS composites containing23%EG/APP/2%HNTs was improved to 29.8 from 18.0 of the composites without HNTs,and the vertical burning(UL-94)could reach V-0 rating.The peak of the heat release rate(p HRR)was reduced by 14.1% and the total smoke production(TSP)was reduced by 12.8%,while the mechanical performance was also improved.The HNTs and EG are cross-modified with each other during combustion to construct a three-dimensional structure,which has an inhibitory effect on heat as well as smoke release.(2)The bio-based phytic acid(PA)was grafted onto the surface of EG to form PA-EG.Then PA-EG and APP were melting blended with ABS to prepare flame retardant ABS composites.It was found that by adding 15%PAEG/5%APP to ABS,the flame retardancy of the composites was greatly enhanced compared to that of the ABS composite sample containing15%EG/5%APP.The LOI was increased to 27.5 and the UL-94 reached V-0rating.The p HRR was decreased by 21.7% and the TSP was decreased by18.5%,while the mechanical performance did not decrease obviously.The addition of PA-EG could form a dense carbon layer with a net-like crosslinked structure.(3)A silicon-boron resin was synthesized and encapsulated on EG to prepare B-Si-EG,which was then blended with DOPO and ABS to prepare flame-retardant ABS composites.The results showed that presence of 8%B-SiEG/7%DOPO in ABS improved the flame retardancy of the composite significantly compared with 8%Si-EG/7%DOPO and 8%EG/7%DOPO.The LOI was increased to 29.2,and the UL-94 was improved to V-0 rating.The p HRR was decreased by 29.2% and the TSP was decreased by 12.6%compared to 8%EG/7%DOPO.In addition,the addition of styrene maleic anhydride as a compatibilizer improved the flame retardancy under different injection molding conditions,the LOI was increased to 27.9,and the UL-94 was improved to V-0 rating.The addition of B-Si-EG reinforced the strength of the carbon layer,reduced the heat and smoke release,and improved the mechanical performance of the composite.