Effect Of Tensile Fatigue On The Evolution Of Micro-mesostructure Of Filled NR And NR/NBR Blends

In this paper,different types of carbon black?CB??N234,N326,N339?filled NR,silica filled NR and CB filled NR/NBR blends were studied by means of DMA,NMR,SEM,TEM and BDS.The evolution of micro-mesostructure and properties during the fatigue process of filled NR and NR/NBR blends were investigated.The results showed that the storage modulus at low strain?E₀'?of NR filled with different types of CB gradually decreases after fatigue,and then gradually increases.The decrease of storage modulus is mainly caused by the destruction of the filler network and the macromolecule crosslinked network.Subsequent increase in storage modulus is due to rearrangement of the CB aggregates and orientation of the molecular chains between the neighbouring CB aggregates.It is found that the influence of the CB structure is much more obvious than that of the CB particle size.For the CB and silica filled NR system,respectively,the fatigue life of each system gradually decreases with increase of the filler content.However,the fatigue life of the CB filled system decreases more than that of the silica filled system.The fatigue life of the silica system is longer than that of the CB system.After tensile fatigue,the filler aggregates rearrangement phenomenon appears in the CB filled system,and the fillers aggregates exhibited local aggregation in silica filled system.The glass transition temperature of the two filled systems increases after fatigue.The results of SEM observation show that the micropores appeared in the cross section of the CB filling system after fatigue.The cross section of the silica-filled system is smooth and flat,and no obvious microvoids appeared.It was mainly caused by the interaction between the filler and the molecular chains.It is related to the different reinforcing mechanisms of the two filler filled systems.For the CB filled NR/NBR blends,the fatigue life gradually decreases with the increase of NR content,and the fatigue life is the shortest when the NR content is 70phr.It is found by TEM observation that the CB filler is more likely to be segregated in the NBR phase,and the CB is more likely to aggregate.The stress concentration is more likely to occur during the fatigue process,and the fatigue failure process is accelerated.Fatigue tests are carried out for different NR/NBR blends.Different degrees of aggregation occur after fatigue,which is related to the segregation of the CB filler.The change in the rate of relaxation after fatigue is mainly caused by different filler-rubber interactions resulting from the segregation of the filler.