Study On Segregation Behavior Of Reinforcing Fillers In NR/NBR Blends

In this work,the segregation behavior of reinforcing fillers such as silica,carbon nanotubes and carbon black in NR/NBR blends was studied by changing the amount of fillers and the blending ratio of rubber,using dynamic mechanical analyzer,transmission electron microscope,dielectric relaxation spectrometer and electronic tensile tester.The effect of filler segregation behavior on the properties of NR/NBR blends was investigated and the effect of the third component SBR on the segregation behavior of carbon black in NR/NBR/(SBR)blends was studied.The experimental results showed that different fillers had different segregation rules in the same compound(NR/NBR).In NR/NBR vulcanizate,the silica was easy to segregate in the natural rubber phase,and the segregation ratio was almost independent on the filler content.However,the different mesostructures were formed with the change of the rubber blending ratio.The silica was segregated in the NR phase,and both of the silica and the NR phase formed agglomerated structure,when the NR/NBR was 25/75.The silica was segregated in the NR phase,and both of the silica and NR phase formed banded structure,when the NR/NBR was 50/50.The silica was evenly dispersed in the NR phase,when the NR/NBR was 75/25.The Payne effect was the strongest(silica 20phr-40phr),and the reinforcement effect,elongation at break,tensile strength were lowest,when the NR/NBR was 25/75.The Payne effect was the weakest,and the reinforcement effect(silica 40phr),elongation at break and tensile stress-strain hysteresis loss(silica 40phr)were the largest,when the NR/NBR was 75/25.The segregation behavior of CNTs in NR/NBR blends was mainly affected by the blending ratio of rubber matrix.When the content of natural rubber in rubber blends was 10 phr,30phr and 50 phr,carbon nanotubes were more easily distributed in NBR phase,and the morphology of CNT aggregation was curly.The CNT spanned both of the NBR phase and NR phase,because of the limitation of the NBR phase size,when the content of natural rubber is 70 phr and 90 phr.In this case,the CNT mainly located at the NBR phase and formed the entanglement structure with the molecular chain of natural rubber.Therefore,the model of "island phase reinforcement structure" was proposed.The Payne effect,low frequency conductivity,tensile stress-strain hysteresis loss,elongation at break and tensile strength of NR/NBR blends increased first and then decreased with increase of NR phase content in NR/NBR blends.The carbon black segregation behavior and the properties of the rubber blends were changed obviously,when the SBR phase was incorporated into the NR/NBR blends.Some of the carbon black aggregates,which originally segregated in NBR phase,distributed in SBR phase.It reduced the relative content of carbon black in NBR phase.Compared with the NR/NBR blends,the Payne effect and low frequency conductivity of NR/NBR/(SBR)blends decreased,while the elongation at break and tensile strength of NR/NBR/(SBR)blends increased.