The Flame Retardancy Application Of Surface Modified Magnesium Hydroxide In Epoxy Resin And EVA Resin

Magnesium hydroxide(MH) as additive flame retardant has characteristics of additive, flame retardant, and smoke suppressibility, and it is also called green flame retardant with nontoxicity, environmental protection, low-cost, and abundant raw material et al. It is the one of the main halogen-free flame retardants because of large usage amout, which has shortcomings as strongly surface polar, easily aggregation, less effective; among this decrease the mechanical properties of a flame-retardant polymeric material. In this paper, we have prepared modified MH with vinyl triethoxy silane coupling agent as a modifier, and added to epoxy resin(EP) and ethylen vinyl acetate(EVA), and their flame-retarding, mechanical properties, thermal stability, and thermal degradation. What’s more, with the compounding use of aluminum hypophosphite and modified MH, the flame-retarding and mechanical properties of EVA resin were investigated in order to increase flame-retarding efficiency and decrease addition amount.Firstly, modified MH particles are prepared by surface modification method with vinyl triethoxy silane coupling agent(VTES) as surface modifier. The influence of synthesis parameters on the hydrophobicity of magnesium hydroxide particles were studied by sedimentation experiments, such as the mount of reaction time and temperature, and reaction materials. The particle size and its distribution, morphology, crystal phase, and thermal behavior of the product were characterized through sample analysis with X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), particle size analysis, Energy dispersive X-ray spectroscope(XPS), contact angle, and so on. The results show that the product obtained with this method has higher contact angle, smaller particle size, and longer sedimentation time. The FTIR analysis proves VTES are bonded onto the surface of MH with a stable chemical bond, which could increase the dispersion and stability.Secondly, unmodified MH and modified MH were added in EP. The flame retardant properties, thermalstablity, and thermal pyrolysis were studied by limited oxygen index(LOI), the smoke densities rating values(SDR), vertically burning, TG, and scanning electron microscopy(SEM). Also, the possible retardant mechanism was provided. When the additive amount of unmodified MH and modified MH both reached to 50%, the LOI values increased from 20.5% reached to 27.6% and 30.1%, respectively, and the SDR values decreased from 96.3% to 67.83% and 61.73%, respectively. Flame-retarding EP could increase the release amount of H2 O, decrease combustible micromoleculars(CxHy-), and benzene and benzene derivatives during pyrolysis. Therefore, modified MH could effectively increase flame-retarding of EP.Thirdly, modified MH and unmodified MH is added into ethylene vinyl acetate copolymer(EVA) the obtain EVA/MH composite. Its flame-retardant properties, flame retardant mechanism and mechanical properties are investigated by limit oxygen index(LOI), horizontal flame test, smoke density rate(SDR), thermo gravimetric analysis(TG), scanning electron microscope(SEM) and tensile test. When 50% MH and 50% modified MH are introduced to EVA, the composite show better flame retardantcy with a increasing LOI from 18.5% to 23.5% and 27.5%, and a decreasing burin rate from 34.61mm/min to13.79mm/min and 12.00mm/min, respectively. However, tensile strength decreases from 30.87 MPa to 17.33 MP and 19.98 MPa. Therefore, it can be concluded that the EVA shows increasing flame retardantcy with the introduction of modified MH, and the decomposion process is changed by modified MH.Fourthly, the addition of aluminum hypophosphite(AlPH) into EVA/MH samples as a synergist is carried out and investigated by LOI, horizontal/vertical flame test, SEM, TG and tensile test. When the 1% Al PH and 50% modified MH are added into EVA,the LOI increases to 31.1%, and tensile strength changes to 19.30 Mpa. As to EVA/1% AlPH /50% unmodified MH sample, the LOI and tensile strength is 58.5% and 14.65 Mpa, which is lower than EVA/1% AlPH/50% modified MH sample. It is conclude that the addition of AlPH into EVA/MH samples can increase its flame retardantcy dramatically and have only a little effect on the tensile strength.