Surface Modification Of Magnesium Hydroxide And Its Application In Polyethylene Retardant Composites

With the increasing attention to environmental protection, low toxicity and low smoke have become important factors in evaluating the flame retardant properties of polyethylene materials and other polyolefin. As the surface of magnesium hydroxide and polyethylene is hydroophilic and hydrophobic, respectively, surface modification of magnesium hydroxide is necessary to improve the surface physical and chemical properties and to enhance its compatibility with the polyethylene material, as well as to maintain the mechanical properties of flame-retardant polyethylene, and so on.In this study, the dry process modification of magnesium hydroxide was conducted. The effects of modification temperature and the amount of modification agents and modification time on activation index of magnesium hydroxide have been studied. It's found that the activation index of modified magnesium hydroxide increases with the increasing of modification temperature and the amount of modification agents and modification time. The optimal modification conditions for magnesium hydroxide are modification temperature is controlled to be 80℃, the modifier amount of magnesium stearate and KH570 compared to the weight of modified magnesium hydroxide powder is 2.5% and 0.5%, respectively, and the modification time is 3h. The activation index of magnesium hydroxide powder modified in optimal modification conditions reaches 98% or more. It's found from FTIR, XRD and SEM that particle polarity of magnesium hydroxide modified has been reduced and dispersion of powder has been obviously improved. In this paper, the modification of magnesium hydroxide/zinc borate compound system has also been studied.The modified magnesium hydroxide and polyethylene have been blend together. With the increasing addition of magnesium hydroxide, the tensile strength and the LOI value of magnesium hydroxide/polyethylene composites have been decreased and increased, respectively. When content of magnesium hydroxide is 20%, the loss tensile strength of modified magnesium hydroxide/polyethylene composites and unmodified magnesium hydroxide/polyethylene composites is 8.22% and 1.98%, respectively. When content of magnesium hydroxide reaches 35%, the LOI value of modified magnesium hydroxide/ polyethylene composites and unmodified magnesium hydroxide/polyethylene composites is 26.0 and 24.6, respectively. It's found from the result of DSC, TGA and SEM of tensile fracture that modified magnesium hydroxide has more good thermal stability, processing properties and has better compatibility with polyethylene composites.In this study, the compound system of magnesium hydroxide and zinc borate has been blend with polyethylene. When the amount of flame retardant reaches 35% of the total mass of the composite, with the change of ratio between magnesium hydroxide and zinc borate the tensile strength of flame retardant PE change from 19.0 Mpa to 20.6MPa. With the ratio of zinc borate appropriate adjustments, the LOI value of blends remained at 25.0 or so. It's found from SEM and other tests that the properties of process and thermal stability of polyethylene have been effectively improved and the retardant particles has better compatibility with the matrix of polyethylene.