Synthesis and characterization of water swellable natural rubber vulcanizates

Cassava starch-g-polyacrylamide superabsorbent polymer (SAP) was prepared by a reactive batch processing. Superabsorbent polymer composites (SAPCs) were prepared by blending the SAP with bentonite. Water swellable natural rubber (WSNR) was then prepared by blending high-ammonia natural rubber latex or dry blending of epoxidized natural rubber (ENR) or maleated natural rubber (MNR) with SAPC, poly(ethylene oxide) (PEO) and trimethylolpropane trimethacrylate (TMPTMA). WSNRs containing 10 phr PEO and 2 phr TMPTMA gave higher mechanical strength and water absorbency. Increasing the PEO loadings (20–40 phr) rendered higher absorbency with lower mechanical strength. A higher scorch time and cure time with a lower crosslinking density and cure rate index were found in the MNR-modified WSNRs compared with the unmodified WSNR or ENR-modified WSNR. ENR- and MNR-modified WSNR exhibited highest water absorbency with lower mechanical strength compared with the unmodified NR-based WSNR. The SAP and vulcanized rubber were thermally degraded under oxygen atmosphere, whereas 11% of the residues were bentonite and ZnO.