Nano-reinforced Modification On RFL Fiber Impregnation System And Study On Novel Environmentally Fiber Impregnation System

High performance fibers and composites are one of the key development directions in the field of advanced composites materials and structures.With the development of the national large aircraft industry,the application of fiber/rubber composites to large aircraft tires has become an urgent issue.The use environment of large aircraft tires with high speed,high pressure and wide temperature range is easy to cause adhesion damage of rubber and fiber,which requires a higher bonding strength of the interphase layer.The traditional Resorcinol-Formaldehyde-Latex(RFL)impregnation system which is the most common used method in industry is also difficult to achieve the strict application requirements,and the RFL system needs to be modified.In this paper,silicate nanofibers——attapulgite(AT)is chosen to modify RFL impregnation system.It is easy to decompose into single crystal and has high aspect ratio and high modulus,and there are a lot of hydroxyl groups on the surface of single crystal,and it is easy to form interface hydrogen bond.At first,AT was modified by Amino functional group silane(KH550)to reduce the self-polymerization effect,and then 400W ultrasonic treatment was carried out for 40mins to realize the nano dispersion of AT in the solution.SEM and TEM were used to characterize the dispersion of AT.The experimental results show that AT is dispersed in the form of nano-single crystal in RFL solution,and RFL solution modified by AT can still be uniformly coated on the fiber surface.AT nano-reinforced RFL system significantly improved the adhesion strength level of the original RFL.When the addition of AT is equivalent to 7.5wt%of the solid content of latex,the H pull-out force of nylon 66 cords/rubber composites reached 181.5N,which is 21.5%higher than that of pure RFL(149.4N),and the peel force of single cord reached 31.5N,which is 18.9%higher than that of pure RFL(26.5N).SEM was approached to observe the surface of fibers after extraction and peeling test.The result showed that the damage of composites occurred in the rubber layer instead of interphase layer,which indicates that the adhesive strength of RFL interface layer strengthened by AT is ideal.The addition of nano-dispersed fillers to the RFL can strengthen the impregnation layer and improve the stress distribution,increase the cross-linking density of impregnation layer to withstand higher stress,thus enhancing the stress transfer efficiency,and improving the adhesion property between the fiber and the rubber matrix.Although the adhesion effect of RFL impregnation treatment is excellent and the production cost is low,resorcinol and formaldehyde in RFL have been classified as a carcinogen category by organizations at home and abroad,which are harmful to human health and production environment.Therefore,it is urgent to develop novel non-RF environmentally fiber impregnation technology.In recent years,for various environmentally impregnation systems,their adhesion effect is still difficult to reach the level of RFL.In this paper,we designed the polymer B-adhesion I-VPL environmentally impregnation system of which can replace formaldehyde and resorcinol,composed of maleic anhydride grafted polymer B(with-MAH)and adhesive I(with-NCO).The main reaction of the system was characterized by FTIR and the better curing temperature and time were determined by DSC.By adjusting the solid content of B and the molar ratio of-MAH/-NCO,the best formula was obtained:when the solid content of B is 2.5%,the molar ratio of-MAH/-NCO is 1:0.8,the H pull-out force can reach 92.2%of RFL,and the peel force can reach 90.6%of RFL.SEM was used to observe the impregnation effect of fiber surface,and it was found that the surface of treated fiber was impregnated uniformly.The adhesive level of the environmentally system was further improved by adding a proper amount of nano-AT.It was found that when the addition of AT is equivalent to 5wt%of the solid content of latex,the H pull-out force of nylon 66 cords/rubber composites reached 159.2N,which is 15.6%higher than that of the non-AT group(137.7N)and 6.6%higher than that of RFL,and the peel force of single cord reached 27.3N,which is 13.7%higher than that of the non-AT group(24.0N)and 3.0%higher than that of RFL,the adhesive level is slightly better than that of RFL impregnation system.