| With the increasing demand for high performance rubber products, the high performance fiber framework materials witnessed a rapid development.Nowadays, aramid fiber is becoming one of the main high performance framework materials for rubber composites. Compared with traditional framework materials, aramid fiber exhibits excellent mechanical properties,heat resistance and chemical stability. It has been applied in the fields such as tires?conveyor?and rubber hose. Ultra-high molecular weight polyethylene (UHMWPE) fiber possesses superior mechanical propertites such as tensile strength, shearing resistance and impact resistance, excellent light stability and corrosion resistance, which shows potential application in rubber industry. However, due to the high crystallinity, smooth and chemical inertness surface, both aramid fibers and UHMWPE fibers show a bad interfacial interaction with rubber matrix. The biomimetic surface modification by dopamine is independent with the nature of substrates and environmental friendly, which is a novel and convenient method. It can effectively improve the interfacial adhesion of the above mentioned fibers with rubber matrix. However, the high price of dopamine limits its application in industry. As far as we know, the key reason for the superior adhesive property of dopamine is its catechol and amine groups. In response to this, we choose two cheap monomers of catechol and polyamine, which is less than 1% price of dopamine, to replace dopamine. Tannic acid (TA) is one of most important plant polyphenols, which contains abundant catechol and pyrogallol moieties, is capable of a high binding affinity and forming highly stable complexes with metal ions. Gamma ray irradiation is a novel method for fibers surface modification, which does not need initiator/catelyst and specific temperature. In this paper, the above three method were used to improve the interfacial adhesion property of aramid fibers and/or UHMWPE fibers with rubber matrix. Detailed content is as follows:(1) Surface modification of aramid fibers was successfully developed by the catechol/polyamines co-deposition and followed silane coupling agent y-(glycidyloxypropyltrimethoxysilane) (GPTMS) grafting. The optimal reaction condition for the deposition of poly(catechol/polyamine)(PCPA) on aramid fibers surface was determined as follows: the combination of catechol/tetraethylenepentamine (TEPA) with a molar ratio of 3:1 and a pH value of 9.5. The grafting efficiency of GPTMS was controlled by adjusting the reaction temperature and monomer concentration.Through introducing the epoxy groups on fibers surface which could take part in the vulcanization of rubber, the interfacial adhesion of aramid fibers/rubber composites was significantly improved. Compared with the method by dopamine, this method shows less pre-deposition time on aramid fibers surface of PCPA (3 h) than that of PDA (4 h), and lead to a higher improvement in adhesion force (83.3%) than that by dopamine (67.5%). In addition, the cost of catechol/polyamine is less than 1% of that of dopamine.With advantages of controllable, efficient and low cost, this modification method shows great potential application in rubber industry high performance fiber reinforced composites.(2) Catechol/polyamine co-deposition and secondary functionalization has been proved as an efficient method for fibers surface modification.However, long pre-deposition time limits its further application in rubber industry. In this chapter, two approaches of UV irradiation and the addition of oxidant were used to accerlerate the process of oxidation polymerization and deposition of catechol/polyamine on aramid fibers surface. With UV irradiation, the pre-deposition time for PCPA was shortened to 1 h. Then, the PCPA-coated fibers were further grafted with ethylene glycol diglycidyl ether (EGDE) to introduce epoxy groups onto aramid fibers surface. The effects of EGDE concentration and grafting time on the adhesion force between aramid fibers and rubber matrix were evaluated by pull-out test, and a maximum increase of 85.6% in adhesion force was achieved. As for the addition of oxidant, the pre-deposition time for PCPA was shortened to 30 min. After further grafting of bis-(y-triethoxysilylpropyl)-tetrasulfide (Si69),the pull-out force of the aramid fibers/rubber composites was improved by 42%. This study provides a new efficient strategy for fibers surface functionalization, which has promising application in rubber industry.(3) In chapeter 5, a green and efficient method was developed to improve the interfacial adhesion of aramid fibers to rubber matrix. Tannic acid (TA), a natural polyphenol, can form a metal-polyphenol adhesive coating on fibers surface with ferric iron (Fe?) in a short time. Then, the tannic/ferric iron (TA/Fe?) coated aramid fibers were further grafted with silane coupling agents. Through introducing the active groups of epoxy and polysulfur bonds onto fibers surface, the interfacial adhesion between aramid fibers and rubber matrix was improved by 73.6% and 55.4%,respectively. Compared to the treatment by polydopamine in our previous study, this method is more applicable to rubber industry than polydopamine chemistry due to its cost-effectiveness and short reaction time. Furthermore,the surface modification method based on polyphenol meets the demand of green chemistry.(4) In Chapter 6, both PPTA fibers and UHMWPE fibers were functionalized by gamma radiation-induced grafting polymerization of glycidyl methacrylate (GMA). The simulaneous grafting experimental was conducted wherein the fibers were irradiated in nitrogen atmosphere in the presence of GMA dissolved in methanol solvent. The effect of the monomer concentration on the grafting yield was evaluted. The interfacial adheison between fibers and rubber matrix increases with the increase of monomer concentration, and when the concentration reaches 12 vol%, the pull-out force of PPTA fibers/rubber composites and UHMWPE fibers/rubber composites were improved by 130% and 93.6%, respectively. This method shows advantages of environmental friendly, no need of initiator and short modification time. |
PDF Full Text Request