Water Swellable Rubber Enhanced By Aramid Fibers

Since its inception in the 1970 s,water-swellable rubber has been widely used in the field of sealing and waterproofing due to its excellent elasticity and water swelling properties.With the rapid development of industrialization,people's requirements for the performance of water-swellable rubber products are getting higher and higher,and it is required that the water-swellable rubber can exert the characteristics of sealing and water-stopping according to specific use requirements.The purpose of this paper is to find a filler that allows the water-swellable rubber to maintain the required water swellability while improving its mechanical properties and to make the water-swellable rubber designable.In this paper,aramid was selected as the main reinforcing filler,and the surface of the aramid was modified by phosphoric acid etching.The modification conditions of the phosphoric acid etched aramid were optimized.The phosphoric acid modified aramid structure was analyzed by infrared spectroscopy and scanning electron microscopy.influences.Aramid,modified aramid,nitrile rubber,water absorbing resin and other commonly used rubber processing aids were mixed to prepare water-swellable rubber.Aramid,modified aramid,water-absorbing resin and several processing aids were studied for water swelling.The effect of rubber mechanical properties and water absorption properties,and optimization of the formulation of water-swellable rubber.The prepared modified aramid reinforced water-swellable rubber has excellent mechanical properties,rapid high-rate water absorption,low mass loss rate after water absorption,and good adhesion of modified aramid and rubber.The main research results are as follows:(1)Infrared spectroscopy and scanning electron microscopy analysis of aramid before and after modification.The results show that the amide bond of aramid is partially hydrolyzed,and aramid has many grooves and protrusions on the surface after modification by phosphoric acid etching,which provides favorable conditions for interfacial adhesion between modified aramid and rubber.The modification conditions of phosphoric acid etched aramid were optimized,and the optimum reaction conditions were as follows: reaction temperature was 55 °C,reaction time was 2 h,and phosphoric acid concentration was 30 %.At this time,the contact angle of aramid with water was 58°.(2)When the amount of aramid is 4 parts and the amount of water-absorbing resin is 60 parts,the comprehensive performance of the aramid-modified water-swellable rubber is optimal,and the tensile strength and elongation at break of the water-swellable rubber can reach 3.91 MPa and 163.08 %,Shore hardness increased to 75.The water-absorbing expansion rubber reached the water absorption equilibrium time from 21 days to 6 days,and the equilibrium mass water absorption rate reached 175.34 %,and the mass loss rate was 12.46 %.(3)When the amount of modified aramid is 4 parts and the amount of water-absorbing resin is 60 parts,the comprehensive performance of the water-swellable rubber prepared by the modified aramid fiber is optimal,and the tensile strength and elongation at break of the water-swellable rubber can be respectively Up to 4.38 MPa and 312.75 %,Shore hardness increased to 75.The time for the water-absorbing expansion rubber to reach the water absorption balance is shortened from 21 days to 5 days,and the equilibrium mass water absorption rate is up to 468.17 %,and the mass loss rate is only 7.68 %.(4)Compared with the mechanical properties and water absorption properties of the aramid fiber and the modified aramid fiber prepared by adding the same component,the conclusion is as follows: the aramid skin is susceptible to phosphoric acid during the phosphoric acid etching modification process.The effect of the protrusion or depression,in severe cases will cause the aramid skin to fall off,so that the strength of the aramid is reduced,but the formation of protrusions or depressions will increase the binding force between the modified aramid and rubber,thereby enhancing water absorption Tensile strength of expanded rubber;after aramid etching,the aramid can partially form a hydrophilic group,so that it has better adhesion with the water absorbing resin,and the modified aramid can be better in the water swellable rubber.The ground acts as a water absorbing passage,shortening the time when the water swellable rubber reaches the water absorption equilibrium state,and the water absorbing property of the water absorbing expansion rubber is remarkably improved.(5)Quantitative analysis of the effects of sulfur,carbon black and PEG-6000 on the mechanical properties and water absorption properties of water-swellable rubber.The results show that adding excessive sulfur in the rubber will make the rubber cross-linking network more dense and severely limit the water-swelling property of the water-swellable rubber.As a reinforcing agent,carbon black affects the mechanical properties of the water-swellable rubber.It also affects the water absorption performance of the rubber;adding PEG-6000 to the water-swellable rubber can increase the initial water absorption rate of the water-swellable rubber,and also increase the precipitation of the water-absorbing resin in the rubber,resulting in a decrease in the final water-swelling rate of the water-swellable rubber.The repeated water absorption capacity is weakened,and the mass loss rate of the water swellable rubber is increased,which affects the reusability of the water swellable rubber to some extent.(6)The adhesion and orientation of the modified aramid in the water-swellable rubber were analyzed.The results show that the modified aramid is mainly bonded with rubber by mechanical bonding.Through the shearing action of the twin-roll mill,the orientation of the modified aramid in the rubber can be more than 50 %,which is beneficial to The orientation of the modified aramid in the rubber.The modified aramid-reinforced water-swellable rubber has excellent mechanical properties,rapid high-magnification water absorption,low mass loss rate after water absorption,and good interface adhesion.