Recycling waste tire rubber by water jet pulverization: powder characteristics and reinforcing performance in natural rubber composites

Pulverization is a general strategy used prior to any practical application of recycled waste tire rubber (WTR). Mechanical grinding, in use currently, is an inefficient technique due to low-quality rubber powder production and certain indispensable additional pretreatments. The aim of this study is to propose a novel pulverization technique of WTR by ultrahigh pressure water jet. Efficient pulverization of WTR was accomplished by water jet without any pretreatment. Powder characteristics, including particle size distribution (PSD), surface area, thermal behavior and chemical structure changes, were investigated. The curing, mechanical and morphological properties of natural rubber (NR) vulcanizates filled with ground tire rubber (GTR) from water jet pulverization (WJPULV) were evaluated. The results indicate that GTR granules from WJPULV possess a quite fine PSD and large surface area, show similar thermal degradation behaviors to the original WTR and have been partially devulcanized. The improvement of tensile and tear strength of the composites reveals that GTR from WJPULV can be added up to 40 phr without adverse effect. The morphological analysis corroborates the homogeneity of GTR in the NR matrix. All findings confirm that water jet can be an excellent choice for pulverization of WTR.