EVALUATION OF THE ABILITY OF RUBBER BASED ON BNK TO RE-SWELL UPON CONTACT WITH WATER AND AQUEOUS SOLUTIONS OF SODIUM CHLORIDE

Abstract

Ability of a water-swellable (WS) rubber based on BNK, to re-swell in water and aqueous solutions of NaCl were studied. WS was modified with combination of sodium carboxymethyl cellulose and a copolymer of acrylamide with potassium acrylate. The curing process at 150 °C were studied using MonTech MDR 3000 Professional rotorless rheometer. The physical and mechanical properties of the vulcanizates were determined by a Zwick \ Roell Z010 tensile testing machine at a test speed of 500 mm/min. Hardness and tear resistance were also determined. Besides the mass change (∆m) of WS in process of exposition in water and aqueous solutions of NaCl was measured at room temperature according GOST 9.030-74. The determination of pores presence and their sizes before and after swelling, as well as changes in the elemental composition (in terms of Κ, Na and Cl atoms content) of samples, dried after swelling, were studied by electron microscopy (Versa 3D). The numerical value of whole density of cross links ν_t was obtained from the data on the dynamic shear modulus. Density of chemical bonds ν_ch was determined from the data of equilibrium swelling in toluene according to the Flory-Rener equation. It was fund that after exposure of the samples in aqueous salt solutions, pores of a smaller size are formed in comparison with the samples in contact with water, which correlates with the data on the degree of swelling (∆m change) in these media. After contact with water and aqueous solutions of NaCl, K atoms in the samples are practically not detected. It is assumed that this is due to the partial elution of the copolymer of acrylamide with potassium acrylate, as well as the result of the exchange of K ions for Na.