Flame Retardent Level Magnesium Hydroxide Surface Treatment And Application In Polypropylene

Magnesium hydroxide as a hlogen-free environment flame retardant, with high decomposition temperature, smoke suppression, non-toxic emissions, are widely used in polymer materials. In this thesis, Mg（OH）₂ surface were modified by wet method using silane coupling agent as surfactants,and were characterized by activation index, SEM, FT-IR. Furthermore, the Mg（OH）₂ surface were coated by urea-formaldehyde resin and PS in-situ polymerization. Then Mg（OH）₂ were filled into polypropylene, the influences of adding level, surface modification and particle size of Mg（OH）₂ on the mechanical properties and flame resistance of the Mg（OH）₂/PP composites were investigated. Conclusions as following:（1） Silane coupling agent can improve the hydrophobicity and dispersion of industrial grade Magnesium hydroxide at room temperature by wet method; n-odecyl-trimethoxysilane have good stability in the aqueous solution, can be coated on the surface of Mg（OH）₂ to achieve good surface organic effect. The impact strength of PP containing modified Mg（OH）₂ was 53.5% higher than that of containing unmodified Mg（OH）₂, and the elongation at break was 7 times when it containing unmodified one. The optimum reaction techniques are as follows: temperature at 80℃, dosage at 0.8wt%, reaction time above 60min.（2） Urea-formaldehyde resin coated Mg（OH）₂ composite with film thickness at 80-100nm were prepared by in situ polymerization. The effects of wall material ratio, emulsifier, reaction temperature and reaction pH on microcapsule particle distribution and surface morphology were studied. The optimum preparation techniques are as follows: Proportion of raw material are Mg（OH）₂ 5g, urea 10.1g, 36% formaldehyde solution 27.8ml, pH value at 7⁸, temperature at 70⁸0℃, and use SMA as emulsifier. Meanwhile, Mg（OH）₂/PS composite particle can be get by similar method, the results show that PS coated Mg（OH）₂ particles have a good decentrality, and moderate coating thickness.（3） The flame retardant properties of Mg（OH）₂/PP composite materials have been improved with the increase of Mg（OH）₂ content,but the mechanical performance decreased with Mg（OH）₂ adding, when the addition level was above 40%, mechanical properties severe decline. Modified Mg（OH）₂ are highly dispersed in PP at the addition level of 50%,and the one with the particle size of 800nm have the best mechanical properties;particle size at 150nm or over 800nm have better flame retardant performance.