Photocrosslinking And Related Properties Of Halogen-free Flame Retardant Polyolefins

Metal hydroxides like magnesium hydroxide (MH) have been extensively used in halogen-free flame retardant (HFFR) polymeric materials. However, main disadvantages of MH are low FR efficiency and large additive amount, which damage mechanical properties and seldom meet applications. In this paper, the mechanical and thermal properties of HFFR composites had been improved through synergic and photo-crosslink methods. The results were as follows:1. The synergistic effects of fumed silicon (SiO2) or methyl vinyl silicone rubber (MVQ) with magnesium hydroxide (MH), melamine phosphate (MPP) in the EVA copolymer has been studied. UL-94, Limiting Oxygen Index (LOI) and mechanical property data proved that suitable amount of fumed silica could improve the flame retardant and mechanical property of EVA/MH/MPP/SiO2 composites.2. The synergistic effects and mechanism of melamine cyanurate (MCA) with MH in halogen-free flame retardant EVA/MH/MCA composites had been studied by UL-94, LOI and mechanical tests. The properties of halogen-free flame retardant composites were optimized with different compatibilizers. The data of UL-94, LOI and mechanical property showed that better results could be obtained when suitable amount of EVA-MA mixed with EVA/MH/MCA composites.3. EVA/MH blends and their related properties in the presence of photointiator had been investigated by the measurements of gel content, hot extension test, UL-94, limiting oxygen index (LOI), SEM, thermogravimetric analysis and mechanical measurement. The data from the gel content and heat extension rate showed that the samples could readily crosslinked by UV-irradiation with 1.0 wt% photoinitiator. With 4s UV-irradiation time, the tensile strength (TS) increased evidently, but the corresponding value of elongation at break (EB) slightly decreased. The data obtain from UL-94, LOI, and TGA indicated that photocrosslinking could remarkably improve the flame retardant and thermal properties of EVA/MH samples.4. Photoinitiated crosslink of POE/MH and related properties in the presence of photo-initiator had been studied. Photocrosslinked with 4s UV-irradiation time, the gel content of samples increased to above 87 wt%, and their related tensile strength or thermal aging properties were also improved.