Study On Dynamic Properties Of Nitrile-butadiene Rubber

Nitrile-butadiene rubber (NBR) is a synthetic rubber with good oil resistance, hot air aging, chemical mediator resistance and mechanical properties. So it is the conventional rubber material used in oil drilling, petrochemical industry and automobile with severe dynamic environment. Under this condition, failure of rubber products was caused by mechanical fatigue and heat build-up, which make it a great importance to develop the novel NBR composites with a good dynamic property. Selecting the appropriate curing system, reinforcing agents and coupling agents,and then the mechanical properties, chemical mediator resistance, hot air aging and fatigue properties of NBR vulcanizate were investigated. The effect of filler network structure on dynamic propertries of NBR vulcanizate was characterized by rubber processing analyzer (RPA 2000) and dynamic mechanical analyzer (DMA). At the same time, the microstructure of NBR vulcanizate was observed by scanning electron microscope(SEM).The effect of different curing systems on the propertis of NBR vulcanizates were studied. The results indicated that NBR cured with traditional sulfur curing system showed better tensile strength and fatigue resistance, but with a higher heat build-up. The abrasion resistance of NBR vulcanizate depends on the crosslinking density, the aging resistance of NBR vulcanizate depends on the type of cross-link bonds, and chemical mediator resistance of NBR vulcanizate denpends on both of them. Glass transition temperature of NBR vulcanizates cured by peroxide is lower than thosecured with effective and traditional sulfur curing system. The heat build-up of NBR vulcanizate decrease with the increase of crosslinking density.The effect of coupling agent species and amount, compounding process on the properties of NBR filled with carbon black were investigated. The results told us that the apparent crosslink density and filler-polymer interactions were increased with the coupling agent of Si69 or KH550 content, and filler-polymer ineractions became stronger and mechanical properties of NBR vulcanizates were increased when the compounds mixed at high temperature. The aging resistance of NBR vulcanizates were improved with the incorporation of KH550, especially with 2 phr KH550. Dynamic properties of NBR vulcanizates were highlighted by the adding of Si69 or KH550, while NBR vulcanizates had better dynamic properties with the KH550 and the blends was mixed at high temperature, especially with 2 phr KH550.Study of NBR compound filled with silica/carbon black showed that the network structure of NBR vulcanizates was weakened and the ability of reconstruction of network structure was enhanced when the fillers were in-situ modificated by Si69 or KH550 or both of them. After in-situ modification with Si69, Mooney viscosity, heat build-up and compression set of NBR vulcanizates were decreased obviously, but with better mechanical properties and fatigue resistance. Processability of NBR vulcanizate filled with silica/carbon black was improved obviouslyby processing aids such as Aktiplast T, Aktiplast ST or PEG-4000, which had little influence on mechanical properties, aging resistance and chemical mediator resistance of NBR vulcanizate. Especially for Aktiplast ST system, the network structure of NBR compounds and the aggregation of filler in the process of vulcanizing were broken down, the ability of reconstruction of network structure was increased, the loss modulus was lower, and the fatigue property was better.Effect of carbon black/silica ratio on the properties of NBR was studied, and the the results revealed that with the increase of silica amount, carbon black-carbon black network structure of NBR vulcanizate were gradually broken, silia-carbon black network structure was formed, and carbon black - carbon black network structure in NBR vulcanizates matrix disappeared while 35 phr silica was added. Aging resistance and chemical mediator resistance of NBR vulcanizate were improved, and tanδvalue, heat build-up and compression set were lowered, but the fatigue properties were poor. Generally, NBR vulcanizates have good comprehensive properties with 10 phr silica.