The Properties Research Of Grafted Carbon Black, Silica Used In Natural Rubber

Rubber materials were widely used in transportation, machinery, electronics, defense andother fields of national economic because of its high flexibility, abrasion resistance, insulation,light quality and easy to process, etc. With the progress in civilization and the development ontechnology, the requirements to rubber performance were increasing. It was a more reasonableapproach to improve rubber performance by appropriate treatment of the existing material.Based on this ideal, the research work was carried out in two major areas.Firstly, carbon black and silica were the main reinforcing filler used in natural rubber.They possessed high surface energy and poor coMPatibility with rubber, so they were difficultto disperse in rubber matrix uniformly in mixing process. These characteristics resulted in alimited reinforcement effect when they were mixed with natural rubber in order to improvethe dispersibility and coMPatibility. In situ grafting was selected for surface modification ofcarbon black and silica The effect of filler, which before and after in situ grafting, on theoverall reinforcing performance of rubber was studied. The study was divided into three parts:(1) Study on surface modification of carbon black and reinforcing effects of modifiedcarbon black in natural rubber. The content of oxygen-containing functional groups on carbonblack is low, the effect of direct surface modification of carbon black is poor. For this problem,liquid-phase oxidation was adopted to increase the oxygen-containing functional groups oncarbon black, and then carbon black with oxygen-containing functional groups was reactedwith Polyethylene glycol400in order to introduce the long-chain organic groups on thesurface of carbon black, thus reduce the surface energy and increases steric hindrance ofcarbon black. The effects of different conditions on the surface graft modification of carbonblack were studied. In-situ graft-modified carbon black was applied to reinforce natural rubber.The reinforcing efficiency of carbon black and in-situ graft-modified carbon black werecoMPared. The results showed that: in situ grafted carbon black was conducive to enhancingthe overall performance of natural rubber. In addition, the mechanism of performanceimprovement of rubber was studied.(2) Study on surface modification of silica and reinforcing effects of modification silica filled in natural rubber. The surface silanols of silica was more, it was much easier to carryout the modification reaction. For this feature, solid phase in situ grafting was used as thesilica surface modification method by adding modifying agent during mixing process. Theeffects of different conditions on the situ graft modification of silica were studied. In-situgraft-modified silica was applied to reinforce natural rubber. The reinforcing properties ofsilica and in-situ graft-modified silica were coMPared. The results showed that: in situ graftedsilica was conducive to enhancing the overall performance of natural rubber. Orthogonal testwas used to analyze the iMPact of various modification conditions on performance. Theresults of variance analysis and univariate analysis were consistent. The best modifiedconditions were as follows: the optimum modifier was Si-69, and the optimum dosage was8phr. The dosage of dispersing agent B-52was2phr. The heat treatment temperature was120℃. The heat treatment time was8min.(3) Study on strain softening effect and Payne effect of carbon black, silica-filled naturalrubber were studied. Strain softening and filler reinforcement mechanism of natural rubberwere analyzed. The resulus showed that molecular chain shedding and slip was the mainmechanism of strain softening at low filler loading, but aggregate rupture was the mainmechanism of strain softening at high filler loading.Secondly, grafted carbon black was used for enhancing the strength, abrasion resistanceand the other performance of natural rubber, but was not used for enhancing the flexproperties; silica grafted was used for enhancing the flex properties, but was not used forenhancing the strength of natural rubber. For this problem, the means of natural rubber blendwith trans-natural rubber, carbon black blend with silica were used to improve the overallperformance of rubber.The effects of different trans-natural rubber contents, different curingconditions and different proportions of carbon black and silica on the overall performance ofrubber were studied. Elastic ball joints were prepared according the formula having greatoverall performance, and application performances of elastic ball joints were studied. Theresults showed that the radial static stiffness, axial static stiffness and fatigue of elastic balljoint had been improved by filling in situ graft modified carbon black and silica as filler, at the same time adding10phr of TPI in natural rubber.