Preparation And Characterization Of Halogen-free Flame Retardant EVA Composites

Ethylene vinyl acetate (EVA) copolymer with different acetatecontents has been used extensively in many fields, especially in thecable industry, due to its good mechanical and insulating properties.However, EVA copolymers are particularly flammable and emit a largeamount of smoke during burning, which cannot meet the requirementsfor many industrial application cases. Therefore, it is very important toimprove the flame retardancy of EVA materials.The non-halogen flame retardant EVA was prepared by usingAmmonium Polyphosphate (APP) and Pentaerythritol (PER) as theintumescent flame retardants (IFR). Study IFR with three differentinorganic flame retardant additives which are ZEO/SiO2, Attapulgite(AT)/zinc borate (ZB), and organic montmorillonite (OMMT) inassociation with an IFR sysytem have been used to improve the fireperformance of EVA composites in. The flammability, thermal behaviorand char morphology of EVA composites were investigated by using limiting oxygen index (LOI), vertical burning test (UL-94), thermalgravimetric analysis (TG), scanning electron microscopy (SEM) andcone calorimeter tests etc. The tensile strength and elongation of EVAcomposites were tested. The results show that the addition of smallamount of AT can significantly improve the LOI value. It is found that alittle amount of4A-zeolite could significantly improve the LOI value.The EVA composite containing1phr4A-zeolite has a LOI value of31%and achieve V-1rating in vertical burning test. LOI can be increased to32%and UL-94test can reach V0level when3phr silica is furtheradded. The mechanical properties of EVA composites containing ZEOand SiO2have declined. It is suggested this the first time to use modifiedAT to improve the flame retardancy and smoke suppression of EVA/IFRcomposites. The addition of0.6phr AT can apparently improve the LOIvalue and increase the amount of char residue. The TG and CONE datashow that the addition of AT and ZB can improve the fire performance,thermal stability and smoke suppression. The optimum quantity ofOMMT is4phr. And LOI can be increased to29.4%and UL-94test canreach V0level. The addition of OMMT can enhance the char formationand reduce total heat release and smoke release amount. The addition ofOMMT can play a role of reinforce composites. The addition ofcompatilizer can improve the flame retardancy and mechanicalproperties of EVA composites.