Preparation And Properties Of Starch/Sodium Acrylate/Chloroprene Rubber Water-Absorbent Composites

Water-swellable rubber (WSR) which is a kind of sealing materialshas dual seal and water-stop functions. WSR will expand the functions ofthe rubber which is as a representative of the elastomer material in thefield of water absorption and seal. WSR is a kind of new functionalpolymer elastomer material. WSR has five advantages compared with thesimilar water absorption material as follows, high mechanical properties;good water-absorbent properties; excelent repeatedly expanding andcontracting performance; strong bearing water pressure ability;inoffensive materials. WSR has been possessed wide applications inindustry, agriculture and biomedical materials.This paper aims to explore a kind of WSR, using chloroprene rubber(CR), starch and sodium acrylate (NaAA). Preparation, influencingfactors and the mechanism of water absorption were investigated. Mainresearch aspects are as follows:1. Water-swellable rubber was prepared by latex compoundingmethod. The effects of NaAA and starch on mechanical properties and water-absorbent property were studied. The results showed that30phrNaAA and20phr starch were the optimum compositions. Δm and ΔVreached700%and970%after soaking in water294h at70℃. Waterswelling ratio and water absorption rate increased with increasing theNaAA amount. The starch particles possess dual characteristics:water-absorbing and reinforcing abilities.The morphology of compositeswas shown by transmission microscopy graphs, indicating PNaAA as themain water absorbing component and starch particle possessing a gooddispersing. The composites preparing by LCM were swollen uniformly inwater and kept their original shapes well.2. It can be confirmed that reaction does occur between CR andNaAA after heat processing above150℃, namely nucleophilicsubstitution reaction between a carboxylate carboxylatecarboxylic acidsodium of NaAA and a chloromethyl group of CR. The reaction makesthe network structure of PNaAA with up the network structure of CR andenhances the cross-linking density of the composite, which leads to themore excellent water-absorbent property.3. Water-swellable rubber was prepared by latex compoundingmethod. The effects of the NaAA amount on the properties and salt-andpH-responsive behavior were investigated. It can be seen that thecomposites were high salt-and pH-sensitivity. The mechanical propertiesin deionized water were lower than those in salt aqueous solutions and higher than those in acid or alkaline solutions. The water swelling ratiosin deionized water were higher than those in other solutions. Thisbehavior can be attributed to charge screening effect and corroded effect.The water swelling ratio of the composites in different concentration ofsalt solutions can be accurately predicted. The composites absorb waterthrough interpenetrating network between CR and PNaAA or theindividual network structure of CR and ionic bonding of PNaAA to attachwater. Water exists in WSR with two forms, free water and bondingwater.4. Stacrh/NaAA/CR water-absorbent composites were prepared byblending polychloroprene with starch, NaAA and vulcanizing agents. Theeffects of the different swelling mediums on mechanical properties andwater absorbent properties of Stacrh/NaAA/CR water-absorbentcomposites were investigated in deionized water and NaCl solution bychanging the swelling medium. The results showed that the waterswelling ratios in deionized water were higher than those in NaClsolution. The materials can expand and contract repeatedly due toosmotic pressure. Adopting a new visualized method that is ContactAngle Test describes water absorbing phenomenon. The highercross-linking density is there, the better water-absorbent property. Thestructure of the NaAA Particles changed greatly before and after waterabsorption. PNaAA was the main water absorbing component. 5. The repeatedly used performance of the Stacrh/NaAA/CRcomposites was investigated. It can be seen that the composites whichhave excellent repeatedly used performance can maintain their originalwater absorbent properties by repeated used. And the surface morphologyof the composites remains intact.6. Contrast the properties of the composites preprared by DCM andLCM. The mechanical properties were not much difference by the twomethods. The Elongation at break of the composite prepared by LCM washigher. Both of them had good repeated use properties. But the waterswelling ratios of the composites prepared by LCM were much higherthan those by DCM. So LCM is the better preparation technology ofwater-swellabe rubber.