Nano-reinforced RFL System With Fiber Surfacial Dipping Treatment And Its Rubber Composites Interfacial Adhesive Properties

In the traditional rubber industry,fiber reinforced rubber composites occupy a considerable proportion,and the interface adhesive property is poor due to the large difference in surface energy between fiber cords and rubber.Currently,Resorcinol-Formaldehyde-Latex(RFL)is commonly used in the industry to dip fiber to improve the interfacial adhesion between fiber and rubber.However,at this stage,the adhesion effect obtained by using RFL technology is difficult to meet the various harsh conditions of large aircraft radial tires and heavy-duty tires in service,and further improvement is urgently needed.In this paper,on the basis of RFL dipping treatment technology,different shapes of nanofillers(granular silica and fibrous aramid nanofibers)are used to strengthen the RFL dipping treatment process,and further improve the dynamic and static adhesive properties of fiber/rubber composites,which can be used under more severe conditions.(1)For the silica reinforced RFL dipping treatment system,the influence of the amount of silica on the surface morphology,the rate of coating after dipping and interfacial adhesion of aramid fiber/rubber composites was studied.The relationship between the fiber surface treatment structure and the adhesive properties was investigated.The results showed that with the increase of the amount of silica in the RFL dipping solution,the larger dip pick-up,the rougher the fiber surface after dipping,the more uneven the coating,the H pull-out force,peeling force and dynamic fatigue of the composites all showed a trend of increasing first and then decreasing.This is because a small amount of silica can be uniformly dispersed in the dipping solution,and the surface of the fiber after dipping is relatively uniform,and the addition of silica can increase the modulus and cross-linking density at the interface.In addition,silica can prolong the scorch time,which is conducive to the diffusion of rubber molecules to the interface layer,thereby improving adhesion.However,the dispersibility of excess silica in the dipping solution becomes poor,resulting in an uneven dipped layer and reduced adhesion.When the amount of silica is 8.5wt%,the adhesive effect was the best,the H pull-out force was 200.1N,the peel force of single fiber was 20.8 N,and the fatigue life was 9628 times,compared with the unenhanced RFL system,it is enhanced by 11.0%,18.2%,and 37.0%,respectively.And the location of adhesive failure after dynamic fatigue occurred at the rubber matrix,while it occurred at the interface layer when it is not reinforced.(2)For the aramid nanofiber(ANF)reinforced predipping treatment system and the RFL dipping treatment system,the influence of the addition process and dosage of ANF on the surface morphology of the fiber and the adhesive properties of the composites after dipping were studied.The results showed that both processes would make the surface of the dipped fibers rougher after adding ANF treatment.In addition,a large amount of ANF phase structure would be formed on the surface of the fiber,and with the continuous increase of the amount of ANF,dip pick up would increase,and the surface of the fiber would be rougher after dipping,and the adhesive properties also showed a trend of increasing first and then decreasing.When the optimum amount(only0.05wt%)of ANF was added to the predipping solution,the H pull-out force was 209.0 N,the peel force of single fiber was 19.8 N,and the dynamic fatigue life was 9829 times,which are 18.1%,14.4% and 41.0%higher than those of the unreinforced pretreatment system,and the adhesive failure after dynamic fatigue occurred at the rubber matrix.Added the best amount(0.15wt%)of ANF to the RFL dipping solution,the H pull-out force was 206.5 N,the peel force of single fiber was 19.8N,and the dynamic fatigue life was 8095 times,which are 15.9%,16.1%and 16.1% higher than those of the unreinforced RFL system,and the adhesive failure after dynamic fatigue occurred at the interface.Adding ANF to the predipping treatment system can effectively improve the dynamic adhesive properties,because the ANF has a good chemical effect with isocyanate in the predipping solution,which is beneficial to the modulus transition at the interface and improves the stress transfer efficiency.The addition of ANF to the RFL system can also improve the modulus of the interface layer,which is conducive to stress transfer,but the phenolic resin itself in RFL is very rigid.After adding ANF,the rigidity is enhanced,which is not conducive to enhancing the dynamic fatigue properties of the composites.This topic provides a new idea for improving the adhesive properties of fiber/rubber composites,and the process of using silica to enhance interfacial adhesion is simple,inexpensive,and has industrial application prospects.