Preparation Of Hydrophobic Silica And Its Performance In SBR

The nanosilica powder is hydrophilic inorganic compounds and has hydrophilic hydroxylgroups on its surface, it is readily to aggregate during the synthesis. The nanosilica is difficultto be dispersed uniformly within polymer matrix due to its bad affinity with inorganicpolymer, which endows the composites with defect on the interfaces. The modification ofnanosilica surface-hydrophobic can depress the aggregation of nanosilica during thepreparation and improve the compatibility of nano-silica with polymer.The papers have two parts: in the first part, hydrophobic silica was prepared via thevitriol precipitation method using cheaper water glass as raw material and Si69 as modifier,and was characterized by SEM and FT-IR; in the second part, hydrophobic silica was used inthe reinforcement of styrene-butadiene rubber. The impact of various factors on theperformance of the rubber was deeply studies. The conclusions are as follows:1. Hydrophobic silica was prepared by wet modification method. The silane couplingagent, the modification time and the modified pH value greatly affect the hydrophobic of theproduct. The optimum conditions are as follows: The silane coupling agent: 2.5%; themodification time: 1.5h; the modified pH value: 4.67. Silica has a very good modificationeffect by this process. Its sedimentation volume, the activation index and oil absorption valueshave reached the optimal value, were 4.05mL/g, 98% and 2.86mL/g.2. By performance Comparison of rubber nanocomposites on the preparation of the drymix and wet method, we can find that, the reinforcing effect of the former method is worethan the latter`s. The main reason is that, silica particles can not be well dispersed in rubbermatrix, what reduce the reinforcement of silica particle in rubber.3. The impact of hydrophobic silica amount on the properties of rubber compound:tensile strength and shore hardness increases with increasing hydrophobic silica amount,while tear strength and elongation at break first increase and then decrease with increasinghydrophobic silica amount. 4. By analyzing the properties of styrene butadiene rubber filled with hydrophobic silicamodified by three different slane coupling agents, we can find that, KH570 can form a thick,soft buffer layer in the silica surrounding, what greatly increases elongation at break and tearstrength of the rubber, were 1216% and 37.95N/mm. Si69 and Si75 can form a layer of highcrosslink density around the silica, what increases tensile strength and shore hardness of therubber.5. The addition of hydrophobic silica improves the loss modulus of the rubber, silicon 69of the largest contribution, silicon 75, followed by KH570 minimum. They formed differenttransition layers between silica and rubber. At the same time, the introduction of hydrophobicsilica improved the glass transition temperature of the rubber. Tg of the rubbers filled withSi69, Si75 and KH570 respectively was -25.18℃、-24.38℃and -24.15℃.