The variation of structure and property of sorbitol-treated NR vulcanizates with increasing the silica loading

The endeavour of producing a green tyre tread compound with high silica loading is still a daunting task for all tyre industries globally. The presence of non-rubber constituents, i.e. protein and phospholipid in natural rubber (NR), disrupts the silanization reaction in the silica-filled NR composite. To get rid of that vital issue, an optimized quantity bio-based sugar alcohol sorbitol was introduced at the early stage of mixing as a blocking agent, for improving the silica dispersion and producing a green and sustainable tyre tread compound. A significant improvement in technical key properties like tensile strength, reinforcement index, ARI (abrasion resistance index) ( similar to 9%), HBU (heat build-up) (5 to 8 unit), and rolling resistance (8 to 9% reduction) was evident in sorbitol-treated NR compound, even at higher loading of silica (i.e. silica/CB: 45/5). The functional groups of NR non-rubber substance intervention interrupt the homogeneous filler dispersion, which is verified by the investigation of Payne effect and detailed morphological analysis. The constitutive modelling of the 30 phr silica-loaded sorbitol-treated and untreated NR vulcanizates was performed and fitted to find the best material model based on the correlation factor (R-2 = 0.999). Subsequently, by using Ogden material model constants (N = 4) the cross-link density of all the samples was calculated and compared with their trend of Young's modulus. Based on the overall performances, 30 phr silica-loaded sorbitol-treated compound with 20 phr carbon black was envisaged to be the best compound for tyre tread application.* As cited in Ref [38]

Automated summary

Producing a green tyre tread compound with high silica loading remains a difficult task for all tyre industries globally. The presence of non-rubber constituents disrupts the silanization reaction in the silica-filled natural rubber composite. The introduction of sorbitol as a blocking agent improves the dispersion of silica and enhances the technical properties of the compound.