Study On Halogen-Free Flame Retardant EVA Composites

The flammability of ethylene-vinyl acetate copolymer (EVA) severely restricts its application in related fields. In this paper, aluminium hypophosphite (AHP) and pentaerythritol (PER), AHP and magnesium hydroxide (MH), AHP and nylon 6 (PA6)were used for halogen-free flame retardant EVA, the main results are as follows:A series of EVA/AHP/PER flame retardant composites were prepared by using AHP as flame retardant and PER as synergist, and the related properties of the composites are characterized by means of Limited oxygen index (LOI), UL-94 vertical burner, cone calorimeter (CCT), scanning electron microscopy (SEM),thermogravimetric analysis (TGA), mechanical properties measurements. The results show that when the total amount of flame retardants is 40 wt% and the mass ration of AHP/PER is 4, the LOI is 26% and the UL-94 reaches VO level. With a appropriate amount of PER,the HRR and SPR of the composites decrease, and the carbonation rate of the composites and the compactness of the carbon layer are obviously improved. The mechanical properties of the composites are excellent,which tensile strength amounts to 9.9 MPa and the elongation at break reaches 326%.EVA/MH/AHP composites were prepared by using AHP and MH as flame retardant. LOI, UL-94, CCT, SEM, TG and Fourier transform infrared spectroscopy(FT-IR) measurements show that when the total amount of flame retardants is 52 wt%and the content of AHP is 10 wt%, the LOI reaches 30, and UL-94 pass through VO level. The addition of appropriate amount of AHP leads to the decrease of HRR,MASS and SPR of the composites, improvement of charration rate and compactness of the carbon layer. Moreover, the structure of carbon layer was analyzed by FT-IR and the mechanism of flame retardant was deduced.PA6 and AHP were used as flame retardants to prepare a series of composites with different PA6 contents. The flame retardancy and mechanical properties of flame retardant EVA/LLDPE composites were studied by means of TGA, LOI, UL-94, SEM and mechanical performance tests. The results show that, when the total amount of flame retardants is 40 wt% and the amount of PA6 is 2.5-5%, the EVA/LLDPE composites can reach UL-94 VO level,the tensile strength amounts to 12 MPa,and the elongation at break reaches 1000%.