Constructions of special network structure in natural rubber composites for improved anti-fatigue resistance

Nature rubber (NR) as the most widely used rubber material with excellent comprehensive properties suffers the poor fatigue resistance, which seriously affects the serving life of NR products. Blending crystalline components with NR could improve the fatigue properties of NR. However, the desired structures constructed by the crystalline component in the NR based composites were not clear. Herein, three crystalline polymers including isotactic polybutene-1 (PB), trans-1,4-polyisoprene (TPI) and trans-1,4-poly(butadiene-co-isoprene) copolymer rubber (TBIR) with varied crystallinity and crosslinking ability were selected to blend with NR for various network structure construction. The influences of unvulcanized PB and crosslinkable TPI and TBIR on the polymer network structures, filler network structures and then properties of the final composites were studied. It was found, although the modulus and hardness of both filled and unfilled NR/PB (90/10) vulcanizate improved, while the dynamic properties like heat built-up and fatigue resistance decreased greatly when compared with that of NR vulcanizate. While, NR/TBIR (90/10) vulcanizate showed the highest fatigue life. The structures of unfilled and filled NR/TBIR vulcanizates were analyzed to acquire the desired structure for satisfied fatigue properties of NR based composites. The more homogeneous rubber matrix enhanced with nano-scale crystalline lamellar structures and having co-vulcanization crosslinking bonds between NR and TBIR contributed to the greatly improved fatigue resistance, as well as satisfied other mechanical properties.