Study On The Preparation Of Water Swellable Rubber With Nitrile Rubber Modiifed By Alkaline Hydorlysis

Water-swellable rubber(WSR)is a novel functional material with excellent elastic and swellableproperties. In the preparation of water-swellable rubber, it shows that NBR presents hydrophobicitywhile absorbent resin shows hydrophilia and great polarity difference exists between them. Thereforethrough physical blending method to produce WSR, uneven blend is occurring in water absorbentresin and NBR all the time. Furthermore problems are generated because of the decrease in servicelife of WSR and the limit in its application prospects.In order to solve these problems, the Nitrile hydrolysis reaction can be applied to partiallytransform NBR nitrile groups into hydrophilic carboxy groups. Within the complex environment,nitrile rubber (NBR) can be used for a long time since it has good oil and aging resistance and its heatresistance is better than natural rubber, butylbenzene rubber and neoprene. Thus, NBR is suitable tobe the elastic matrix of WSR and two improvements has been obtained using the Nitrile hydrolysisreaction. First, consistency between water absorbent resin and NBR increases along with the polaritydifference reduced. Additionally, during the production of water swelling NBR, the problem that largeamount of mass loss in water absorbing is going to be solved. Finally, its practicability would beimproved.In alkaline environment containing H2O2,NBR nitrile groups can be partly hydrolyzed. Underthis condition, the nitrile groups are hydrolyzed to hydrophilic amide groups and further hydrolyzedto carboxy groups.After conducting FT-IR test in the hydrolyzed NBR, the results indicate that both characteristicpeaks of carboxyls and nitrile groups can be found in infrared spectrograms. Also, through acid basetitration test within the hydrolyzed NBR. it shows that the nitrile groups have relative low hydrolysisrate and the maximum hydrolysis rate is:G max=6.6%. The reason for these phenomenon is that thephase separation of nitrile rubber solution happens easily during the hydrolyzing process of NBR. So only a small amount in dilute phase NBR can be hydrolyzed and the NBR hydrolysis rate is low.From polymer distribution in two phases exiting in the phase separation, the range of theoreticalderivation for the hydrolysis rate of NBR is calculated as:0G9%. So the maximumhydrolysis rate meets with its range of theoretical derivation.In this project, the hydrolyzed NBR is utilized as the matrix, and sodium polyacrylate is used aswater absorbent resin. In the production of swelling NBR using physical blending method, researchon how the usages of involved chemicals including swelling resin, white carbon black, PEG-6000aswell as sulphur affect mechanical properties. Based on the results, the swelling ratio is687.96%when100phr hydrolysis NBR,0.5phr water absorbent resin,20phr white carbon black,8phr PEG-6000and100phr sulphur are used in the experiment. Therefore, the product has excellent mechanical propertiesand low rate of mass loss.Observing with SEM, compared with swelling NBR without hydrolyzing, the hydrolyzed NBRhas more uniform micro structures on cross sections. That is to say, water absorbent resin is welldistributed in the NBR if the NBR matrix is hydrolyzed. As a result, the challenge in poor consistencyis figured out. More importantly, the quality loss swelling rubber during water absorption is undercontrol.