Nanosheets of graphene oxide (GO) were incorporated into natural rubber (NR) to investigate the influence of the partial substitution for carbon black (CB) with GO on the crosslink structure and properties of NR composites. The results show that the dispersion of the fillers was improved by a few GO nanosheets instead of CB. The dynamic and static mechanical properties were improved by using a few GO nanosheets worth of substitution content. The NR/CB/GO (NG) composites show the lowest heat buildup value when the load of nanosheets is 1 phr, which corresponds to only 9°C. However, the comprehensive performance of the composites was poor, or even deteriorated, as the GO tended to aggregate due to the high concentrations.
The effects of substituting carbon black (CB) with multiwall carbon nanotubes (MWNTs) on the structure and properties of natural rubber (NR)/CB composites is explored. Compared with NR/CB composites, NR/MWNTs/CB presents better filler dispersity and dynamic properties of the MWNT up to a certain concentration, as confirmed by scanning electron microscope, dynamic mechanical analyser and rubber processing analyser. Sample with 1 phr MWNTs shows obviously the highest tensile strength, 28.60 MPa, and almost the lowest heat build-up, only 9.6°C, and it is attributed to that not only large cross-link density and better filler dispersity but also high effective elasticity and large filler-rubber interaction. However, when the concentration is much higher, MWNTs tend to aggregate and lead to the poor efficiency to enhance the dynamic properties of rubber composites or even deteriorate the properties.
The stress analysis of rubber liner is widely used in the design of high vacuum elastomer sealing structure. It is very important to determine a reasonable constitutive model and establish a strength evaluation method suitable for failure mode. A series of mechanical properties tests of JY7766 fluororubber were completed in this paper, and material parameters under different constitutive models and strain levels were fitted. A model selection method based on stiffness relative deviation of liner as evaluation index was proposed, and the high precision constitutive model and material parameters with only 0.2% stiffness relative deviation was determined. At the same time, the consistency of crack propagation path and Mises stress distribution of liner was confirmed based on the comparison between theoretical calculation and the actual structure. Under the condition of ensuring the contact total stress of main sealing surface, the maximum Mises stress was reduced by 43.6% and the safety margin of structural strength was improved by optimizing the sealing groove size of a vacuum equipment. The test result showed that the optimized structure meet the requirement of sealing performance.
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