Enhanced Fatigue Properties Of Nr Composites Filled With Graphene Hybrid Filler

Natural rubber(NR)is widely used in the manufacture of tires,conveyor belts,shock absorbers and rubber gloves due to its excellent physical and mechanical properties.However,some defects would be introduced into the rubber products inevitably during the preparation.Under dynamic loadings,these defects would become crack initiation points and further expand to be macro-cracks,eventually leading to the fracture of rubber composites and bringing huge harm and economic losses to the society.The type and amount of filler directly affect the filler's dispersion,the network structure and the interface between the filler and the rubber matrix,which affect the fatigue properties of rubber composites.In this research,spherical carbon black(CB),fibrous carbon nanotubes(CNT),and flake graphene oxide(GO)were chosen as fillers.The effect of filler content,size effect and composite effect on the fatigue property of natural rubber was studied.Firstly,GO/NR composites were prepared by the emulsion method.The effects of the size and content of GO on the fatigue properties of NR composites were fully studied.With the increase in GO content.The strain inducing crystallization(SIC)of NR composites was smaller,which was conducive to improving the fatigue resistance of NR composites.With the increase in GO content,the crack growth rate of NR composites showed a downward trend under the same tearing energy during the crack growth process.However,only when the GO content was more than 2 phr,the crack tip appeared complex morphologies such as deflection and branching,which was beneficial to reducing the crack growth rate.The S-N curves showed that the fatigue lives of NR composites decreased with increasing strain under uniaxial tensile load conditions.Under the same strain,GO/NR composites with 3 phr GO had the longest fatigue life.By calculating the crack precursor sizes of the NR composites,it was found that as the GO content increased,the average crack precursor sizes of the NR composites decreased,indicating that NR composites with more GO had smaller original defect size and longer fatigue life.Secondly,GO-CNT/NR composites were prepared.TEM images showed that CNT and GO were interspersed with each other,which effectively reduced the agglomeration of CNTs.CNT and GO were oriented during stretching,which improved the crystallinity of the NR composites.In the crack growth experiment,it was found that the crack propagation paths of the CNT/NR composites were simple.The crack tips of GO/CNT/NR composites appeared branching and deflection,which reduced the crack growth rate.With the increase in the content of GO,the crack growth rate became slower.Under uniaxial tensile load conditions,the fatigue lives of NR composites were directly proportional to the GO content.The crack precursor size calculation results showed that the crack precursor sizes of CNT/NR and CNT/GO/NR composites with 3 phr GO were 206.0 ?m and 163.0 ?m,respectively,indicating that the addition of GO improved the dispersion of CNTs,and reduced the defects sizes of NR composites.Finally,GO and CNTS with nanometer size and large shape factors were introduced into carbon black/natural rubber(CB/NR)composites.The introductions of GO and CNT improved the filler dispersion and SIC ability of NR,causing more branching and deflections at the crack tips and effectively hindering crack propagation in the materials.Under uniaxial and multi-axial cyclic loading,the GO-CB/NR composites exhibited evident advantages on the fatigue resistance and durability among three composites.