Constructing high roughness structure of rubber powder by swelling mechano-chemical method to improve interfacial bonding strength with natural rubber matrix

Preparing rubber powder (RP) from waste rubber and incorporating it into natural rubber (NR) to save NR sources constitutes an effective strategy for the valuable recycling of waste rubber. Nevertheless, the relatively large particle size of RPs produced through conventional manufacturing processes leads to weakened interfacial adhesion between the RPs and NR matrix, thereby impairing the mechanical properties of NR/RP composites. To address this issue, we propose a swelling mechano-chemical method to prepare fine and high surficial-roughness RPs. The swelling mechano-chemical rubber powders (SMRPs) are incorporated into NRs and various characterizations and tests are conducted to investigate the properties of the SMRPs and NR/SMRP composites. Results show that the average particle size of SMRP was reduced to 130 μm from 1100 μm for ordinary rubber powder (ORP), the surface roughness was increased to 34.05 μm from 14.53 μm, and the specific surface area reached 60.06 m²/g. The SMRPs have internal voids on their rough surfaces, which promotes the interspersing, entangling and crosslink of SMRPs and NR molecular chains, resulting in strong interfacial adhesion. When the SMRP addition amount is 3 parts per hundred of rubber (phr), the tensile strength and elongation at break of the NR/SMRP composites reach 29.6 MPa and 517.6 %, respectively, which are higher than those of pure NRs. The abrasion resistance of the NR/SMRP composites is also stronger than that of pure NRs. When the SMRP addition amount is 12 phr, the tensile strength and elongation at break maintain 93.3 % and 94.5 % of that of pure NRs, respectively, showing improvements of 20.3 % and 15.9 % compared to the composites incorporated with common RPs. Furthermore, backfilling with SMRP significantly reduces the rolling resistance of the rubber composites. Therefore, the preparation of SMRPs has a bright application prospect and is of great significance for the development of waste rubber recycling. • Swelling mechano-chemical method is used for fine rubber powder preparation. • Swelling-mechanical force field roughens SMRPs' surface and generates internal pores. • The interspersing and entangling of SMRPs and NR result in strong interfacial adhesion.