| As a type of the synthetic rubber with excellent oil resistance and wear resistance,nitrile butadiene rubber(NBR)has been widely used in the fields such as seals,hoses,tires and bearings,which requires high wear resistance.In order to improve the wear resistance of the NBR-based composite,high performance chopped aramid fiber(AF)as reinforcement filler was introduced into the composites.The main work is as follows:(1)The effects of the introduction of AF and Nylon fiber(NF)on the properties of the NBR-based composites were compared.Influences and their mechanism of the resorcinol-formaldehyde-latex(RFL)system treatment of the two fibers on the mechanical properties and wear resistance of the composites were discussed.The results showed that,compared to the NF/NBR composites,the AF/NBR composites had much lower tensile strength and elongation at break due to the larger modulus difference and weaker adhesion between the fiber and the matrix.When fibers were treated by the RFL system,the fiber/matrix interfacial adhesion was improved.The tensile strength and elongation at break of the AF/NBR composite sharply increased,and became better than the tensile strength and elongation at break of the NF/NBR composite.Furthermore,the untreated AF/NBR composite showed the best wear resistance,which should be attributed to its highest hardness and the tear resistance.(2)Effects of the fiber content and the RFL treatment of fibers on the properties of AF/NBR composites were studied.The results showed that,with the fiber content increase,the tensile strength of AF/NBR composites decreased firstly and then increased.It should be due to the formation of fiber network at high AF content,which could bear the load during the stretching.When fibers were treated by the RFL system,the interfacial adhesion between the AF and the NBR was improved,but the formation of the fiber network was also restricted at the same time.Therefore,the tensile strength of the composites decreased relatively slowly with the increase of fiber content.Furthermore,the addition of AF could effectively improve the hardness and tear strength of NBR-based composites,which was benefit to the improvement of wear resistance of the composites.The introduction of RFL layer reduced the fiber extraction in the friction process,thus reducing abrasive wear,but it had a certain negative effect on the hardness and tear strength of the composites,which was not conducive to wear resistance under high normal load.(3)On the bases of the experimental results in(2),it was confirmed that the introduction of untreated AF and RFL treated AF(RFL-AF)had their own advantages on the properties of the composites.In this part,untreated AF and RFL-AF with a total of 6 phr were introduced into NBRbased composites in a series of ratios.With the increase of untreated AF,the tensile strength and elongation at break of the composites remained stable at first and then decreased,while the tear strength increased firstly and then kept constant.The abrasion test results showed that,the two fibers had a synergistic effect on the wear resistance of the composites.When the ratio of untreated AF/RFL-AF was 1:1,the wear resistance of the composite was the highest,and the wear mechanism was adhesive wear,which was due to its high tear strength and excellent adhesion with fiber/matrix.(4)Three kinds of AF(untreated AF,AP,RFL-AF)with different surface characteristics of low aspect ratio(length 1 mm,diameter 12 ?m)were introduced into NBR matrix respectively,the effects of physical surface treatment(fibrillation)and chemical modification(RFL treatment)of fibers on the properties of the composites were investigated.The results showed that,the introduction of flexible RFL layer improved the adhesion between fiber and matrix and alleviated the interface modulus difference,which was conducive to the strength maintenance of the composites under low fiber content,while the fibrillation of AF was conducive to the formation of physical network,which improved the strength of the composites under high fiber content.Due to the short fiber length,which was easily to form fibrils and aggravate abrasive wear during friction.So,the RFL-AF/NBR composites with the best interfacial bonding showed the highest wear resistance. |
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