STUDY ON FATIGUE OF PARTICLE REINFORCED RUBBER VULANIZATES WITH THREE-DIMENTIONAL STRESS (12)

STUDY ON THREE-DIMENTIONALLY STRESSED FATIGUE OF NR/SBR BRENDED RUBBER

Abstract

Fatigue processes, fatigue life times and fatigue fracture patterns by three-dimentional stresses were investigated with carbon black filled solution-polmerzed SBR; blended rubber of SBR^*, that is modified at the end of SBR polymer chains by functional groups; and NR. The results are as follows: (1) Rubber phases of NR and SBR, and SBR^*. Dissolved structures are formed by polymer chains of NR and SBR (SBR^*) at their boundaries and they become obstacles to propagations of micro-cracks generated by fatigue. (2) Volumes and strengths of entanglements of polymer chains in boundaries of NR/SBR blended rubber are different from those in NR/SBR^* blended rubber. NR/SBR blended rubber has shorter life than in NR/SBR^* blended rubber, because volumes of entanglements of polymer chains in boundaries are decreased by fatigue. (3) Fracture patterns are controlled by velocities of a formation process of anisotropic layer structures and a generation process of surfase cracks. Fractures grow in lateral direction to NR system, because the formation of anisotropic layer strucures is faster. Fractures grow in radial direction to blended rubber systems, because the formation of surface cracks is faster.