Study On The Properties In Foamed Water Swelling Rubber With Matrix Of EPDM/EVA

Water-swellable rubber (WSR) is usually prepared by mixing bubber matrix such as EMDM with hydrophilic water-absorbent resin such as sodium polyacrylate, foaming agent and other fillers. When touching WSR, the water molecules enter in the rubber by diffusing, capillarity or adsorption. Water-absorbent resin in the rubber absorbs water and deforms, which causes the rubber to expand. When the anti-deform force is equivalent to penetrating pressure, rubber reach the water-absorb balance value.The coupling agent is often applied in inorganic/organic materials compound system or organic/organic compound system to enhance the performance of the composite materials. The mechanism is as followed: Tthere are two kinds of groups with different properties in the coupling agent molecule. One can act with the surfaces of inorganic materials (this action includes physics and chemistry actions), the other can act with the polymer matrix. So, the "molecule bridge" is formed between the interface of organic material and polymers. The binding force is strong enough to link those two kinds of materials.In our study, we use coupling agents to modify sedimentary silica in ethylalcohol solution and then introduce the silica into the WSR. Upon this the combination of rubber/coupling agent/sedimentary silica/water-absorbent resin comes into being, the loss of water-absorbent decrease, the water-abortion ability and the mechanical property are improved.There are hydroxyls in ethylalcohol molecules which can react with sedimentary silica. After dipped in the ethylalcohol solution, the hydroxyls on the surface of silica change arid the amount of associating hydroxyls cuts down. Simultaneously, thecapillary structures in coupler-coupler networks adsorb a part of ethylalcohol molecules which forms azeotrope accompanied by the adsorbed water in the network. The above two aspects result in the poor thermodynamic stability of sedimentary silica and weaken the performance of the water-swellable rubber.Compared with the substantialistic water-swellable rubber, the foamed water-swellable rubber has rather better water absorbability. In our study, the blowing agent promoter is applied in the WSR. To a certain extent it decreases the activation energy of foaming agent; the number of the bubbles, the specific surface area and the water-adsorption area increase which weakens the hindrance of mass transfer and prove the hydroscopicity of the rubber.Moreover, we applied two types of chemicals to solve the poor dispersibility for water-absorbent resin in rubbers. One is macromolecular compatibilizer (EPDM-g-MAH), the other is micromolecular coupling agent (KH-560).KH-560 is better.Through the study on the dynamic equilibrium between adsorption and resolution, we bring forward that the compact degree of crosslinking network is a very important factor for the system of WSR. By controlling the technological conditions, we can adjust the compact degree of the crossilinking network and produce a variety of water-swellable rubber products meeting the market demand.