Study On Salt-resistance Water Swelling Natural Rubber

Water swelling rubber (WSR) is a new type of functional material with the presence of rubber and water-absorbent resin. They can be swollen with water several times to its own weight and prevent water leakage from pipes and gaps at the same time. Based on their unique characteristics, WSR can be used as a water-stopping material and mainly applied to subway, underground engineering, civil building and oil field. WSR can be divided into two types according to whether the rubber is vulcanized or not. Unvulcanized WSR has relatively high water swelling abilities but lack of salt resistance properties. Vulcanized WSR has good mechanical properties but has long preparation period and lack of diverse manufacture methods or superior water swelling abilities.Salt resisting water swelling natural rubber (WSNR-s) which had excellent water absorbency in salt solution was prepared with natural rubber latex grafted with acrylic acid sodium and acrylic-amide by using CHP/TEPA oxidation-reduction system. Preparation condition of WSNR-s was discussed. The effects on the swelling ratio of WSNR-s in salt solution with various cation valence and diverse concentration and different environment temperature were measured. The capacity of repeat water adsorption was investigated. The state of water in WSNR-s was studied. Thermogravimetric analysis of WSNR-s was performed. The results show that the swelling ratio of WSNR-s in salt solution decrease with increasing salt concentration and cation valence, increase as the temperature went up. The capacity of repeat water adsorption keeps well. The water in the WSNR-s exist as bound water at first and then increase as free water with the increasing swelling ratio.Dehydration of WSNR-s reach equilibrium at163.5℃.Monomer-crosslinked water swelling natural rubber (WSNR-c) and vulcanized water swelling natural rubber (WSNR-v) which had good homogeneity and different swelling ratio in salt solution were synthesized separately through grafting of acrylic-amide onto NR using formaldehyde and sulphur as monomer crosslinking agent and rubber vulcanizing agent. The effects of different crosslinking modes on crosslink density, storage moduli, water swelling properties and repeat water swelling properties were studied. The state of water in the WSNR, WSNR-c and WSNR-v were studied by DSC. The thermal stability of WSNR, WSNR-c and WSNR-v was preformed by thermogravimetric analysis. The microstructure of the fractured surface was analysised using SEM. The results show that the water swelling ratio and repeat water swelling ratio of WSNR decreased with increasing crosslink density. The storage moduli were enhanced after crosslinking treatment. The bound water absorbency and thermal stability were decreased with increasing crosslinking degree. The network structure was much more compacted after crosslinking treatment.