Rheology of Cross-Linked Poly(Sodium Acrylate)/Sodium Silicate Hydrogels

Abstract

Transparent hydrogels consisting of poly(sodium acrylate) and sodium silicate were synthesized by freeradical polymerization of sodium acrylate (ANa) in an aqueous solution of sodium silicate (i.e. water glass) with the silicate modulus (M) 2.50 and the Midafen R-102 polymer filler, in the presence of sodium thiosulphate/potassium persulphate (NTS/KPS) as the redox initiators and N , Nmethylenebisacrylamide as the cross-linking monomer. The hydrogels, obtained in this way, were rheologically tested, and also the gelling point, dependence of shear stress on shear rate, and oscillation constants were determined. The results indicated that during the cross-linking reaction, which is associated with a gradual building of the three-dimensional gel structure, the reaction mixture changes its rheological behaviour from pseudo-thixotropic at the beginning of the reaction to pseudo-anti-thixotropic in the end. Both elasticity modulus G and viscosity modulus G during the reaction and for the cast samples after 24 h have practically the same values and the phase shift angle δ is below 20 • which means that we obtained a highly elastic material. It was also found that the elasticity modulus G values increase with the content of sodium silicate in the sample.B Joanna Mastalska-Popławska

Water Interactions in Hybrid Polyacrylate-Silicate Hydrogel Systems

“…Polymer-silicate hydrogel samples were synthesized according to the scheme described in our previous publications [42,43]. Their compositions are presented in Table 1.…”

“…Investigation of their mixtures was sporadically carried out [42]. In our earlier works [42,43], we presented the method of preparation and physicochemical characterization of hydrogels based on sodium acrylate and sodium water glasses. In this paper, we focus on presenting the mechanism of polymerization/gelation of the discussed silicate-polymer systems.…”

Effect of Composition on the Physicochemical Properties of Cross-Linked Poly(sodium acrylate)/Sodium Silicate Hydrogels

“…Based on our previous works [23][24][25], silicate-polymer hydrogels, where the silicate part was sodium water glass and the polymer part was sodium polyacrylate, were used as the research material. As a polymer component, from among the available vinyl monomers such as acrylic monomers, methacrylates, vinyl acetates and vinyl alcohol, we chose sodium acrylate due to the fact that its polymer can bind significant amounts of water and polymerize in the presence of other chemical substances, and the polymerization process itself is not complicated.…”