| Two major problems pose in rubber industry:the wastage of valuable rubber and the disposal of waste tires leading to environmental pollution. Therefore, recycling of waste rubber resource is of great significance. Two major approaches to solve this problem are the grinding and desulfurization of waste rubber. Studies have shown that the most effective way to grinding the rubber is when the rubber be in the glassy state. Thus, the effect of several variables and the fragmentation mechanism of the rubber impact study are particularly important. And also the rubber fragmentation influenced by desulfurization on rubber. This paper mainly researches the following aspects: (1) In this paper, scrap tire rubber as the research object. An experimental facility of cryogenic impact pulverizing for single rubber particle is designed and set up. The parameters of pulverizing rubber particle:impact velocity, temperature, rubber size and impact angle are selected as main factors, and a series of experimental investigations are carried out in a wide parameter range. When the temperature is below the glass transition temperature of the rubber, the impact velocity at least 30 m/s, the particles can be broken. It is conducive to the rubber particle breakage by increasing the impact velocity and reducing the grinding temperature. It is found that impact angle within 0°?45° is comparatively ineffective. When the impact velocity, impact angle and ground temperatures are under certain circumstances, the initial particle size is smaller, finer particles are crushed. (2) Microscopic observation of fracture surface establishes an atlas of cryogenically pulverized rubber. Detailed study and analysis of atlas displays the feature of the fracture surface. The mechanism of the formation of the features can be explained by the dynamic mechanical property of polymer and elastoplastic impacting model. The rubber's impact surface occur plastically fracture, and inside of it occur brittle fracture. Four basic and three combined size distribution functions are used to describe the rubber size distribution. It is found, by comparing the results of nonlinear regression, that Rosin-Rammler functions exhibits the highest accuracy. Based on the analyses, a function is established between the parameters Rosin-Rammler functions and the main factors of experiment. (3) Use waste tire rubber ball and rubber powder as the research object. Waste tire rubber was devulcanized with supercritical carbon dioxide as a medium and diphenyl disulfide (DD) as devulcanized regent. Analysis the reaction temperature, DD content, reaction time, reaction pressure influence the desulfurization of rubber. With the increase of the reaction temperature and the desulfurizing agent content, the sol content increases, linking density decreases, the degree of swelling increases, the glass transition temperature increases. Which illustrate these two factors can promote the rubber desulfurization. Reaction pressure and reaction time on a smaller role in promoting desulfurization reaction, when both increases to a certain extent, the desulfurization reaction is no longer carried out. (4) An experimental study on airflow impact-pulverizing of devulcanized rubber. We mainly discuss the rubber fragmentation influenced by desulfurization on rubber, which includes the sol content, linking density, the degree of swelling, the glass transition temperature. In practical engineering applications, you can make the waste tire powder desulfurization firstly, then use grinding equipment to grind the rubber. Under the same conditions, you can get a finer powder. |
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