Colloquia

Samenvatting

The ever growing problem of end-of-life tires has been receiving more attention over the past years, resulting in increased regulations on the management of tire waste. Part of the solution for this problem can be the efficient recycling of rubber from tires, in order to be repurposed for new tires or other products. While there is extensive research done on the use of silanes as a devulcanization aid for several types of rubber, this is not yet achieved for butyl rubber. Therefore inner tubes originating from truck tires were selected as feedstock material in this study to design and optimize a devulcanization process for butyl rubber.

Butyl rubber inner tubes are processed into granulate and devulcanized thermo-mechanically in the presence of a devulcanization aid. This leads to a devulcanizate butyl rubber of which the quality should be optimized, to make it applicable in industry. The method used for optimization is Design of Experiments, in which the various parameters are explored and information is gathered about their effects and interactions. This is used to alter the devulcanization process accordingly. Mechanical tests are used to assess the quality, while specific testing for devulcanized material determines the amount and efficiency of devulcanization. The optimal parameters within a factorial design are used to further optimize and therefore improve the  material quality.

Resulting from this study, there is a strong effect of the amount of devulcanization aid. An excess of devulcanization aid could cause oligomerization of the silane, reducing the overall quality of the material. Furthermore, a combination of high shear, long time and high temperature generally shows too much degradation in the material, while an increase of these parameters separately has a positive effect on the tensile strength. An increased fill factor can improve the material by providing higher shear forces for a short amount of time. Finally, some considerations have to be made in future research, such as compatibility between the polymer and processing oil, effects observed from varying milling time and the effects of error in the measurements on the statistical analysis.