Study On The Dispersion Mechanism Of Nano-Magnesium Hydroxideinto Rubber Matrixes And The Properties Of Resulting Composites

In this dissertation, a novel nano-magnesium hydroxide powder is chosen as a research object. Firstly, the main factors which influence nano-magnesium hydroxide powders to disperse into rubber matrix have been carefully investigated, and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been used to study the dispersion morphology of the nano-Mg(OH)2 into the rubber matrixes with different viscosities and polarities such as nitrile rubber(NBR), Ethylene-Propylene-Diene mischpolymer (EPDM), Styrene-Butadiene rubber(SBR), Silicone Rubber(SiR), etc. The results indicate that the viscosity of the matrix and the matching of the surface energy between rubber matrix and nano-powders play very important roles on dispersion of nano-powders into rubbers, especially for the surface energy matching. By combining the most advanced dispersion models and the results of this study, a modified dispersion model has been proposed, to introduce the factor of the surface energy matching, to study the dispersion of the nano-powders in the rubber matrixes. The experimental results can be well explained by this new dispersion model. Secondly, The networking structure, i.e., Payne effect, of nano-Mg(OH)2 dispersed into the rubber matrix has been exclusively expatiated by Rubber Processing Analyzer(RPA). By combining the observation results of SEM and TEM, the dispersion structure model of the nano-powders has been put forward. It is found that the higher the viscosity of matrix, the better the surface energy matching, the finer the dispersion of nano-powder is, and the more flexible the networking is formed. In other words, the amount of net-points, i.e., the confined rubber polymers or nano-Mg(OH)2 powders, is increasing greatly. On the other hand, the lower the viscosity of the rubber matrix, the poorer the surface energy matching between the polymer matrix and nano-powders, at the low loading contents of nano-powders, the more easily the large agglomerates and local, incomplete networking are formed; at the high loading contents of nano-powders, the more easily the large direct agglomerates are formed to generate a sturdy networking structure, i.e., a rigid, sparse net-points formed.Finally, the mechanical properties and fire resistance of composites were studied in detail. The structure and the property of the Mg(OH)2/EPDM composites under the different particle sizes of Mg(OH)2 powders have been investigated, and their mechanical property and fire resistance of the composites have been compared with that of Al(OH)3/EPDM composites. The better the dispersion of the nano-powders, the stronger the surface interaction between the powders and the matrix, the better the mechanical property of the composites is. It is found that the dispersion of the nano-powders has been greatly enhanced by treating the surface of the powders, and thus increase the strength of the composites by strong surface interaction. It is also found that the mechanical property and the fire resistance of the composites could be greatly affected by the particle sizes of the powders. The smaller the particle sizes of the powders, the better the mechanical property and the fire resistance of the composites are. It is evident that the comprehensive properties of the Mg(OH)2/RPDM composites is superior to that of Al(OH)3/EPDM composites.