The effect of different nanofillers on water uptake and gel point of polysodiumacrylate hydrogel nanocomposite

Hydrogels are polymers formed with some three dimensional networks. These polymers have hydrophilic nature;so can be used in the agricultural, horticultural and drug delivery applications. The aim of the present work was to investigate the effect of cellulose micro fibers, Cloisitenanoclay and silver nanoparticles on themwchanical properties ofhydrogels based on polysodiumacrylate. Such properties arethe gel point (GP), gel strength and swelling behavior. To achieve such properties, poly sodium acrylate hydrogels were synthesizedvia a dilute solution of sodium acrylate monomer. Then, the gel points of samples were measured with different filler content (fillers content ca. 0 to 0.8 wt.% of monomer). First of all, a frequency sweep is taken, and then the Winter-Chambon (WC) criterion was implemented for determining the gel point. Here, the gel time is the point that damping factor remains constant.The results indicate that the samples gel time with fillers shift to longer timeswhilst the other method determines the gel point, from the point that viscosity increases sharply. In WC method at the gel point the gel has reached to a fixed structure, but in viscosity method, the gel time is in its initial step of gelation process and the gel has not possessed a fixed structure. The gel point ranges from 200 to 300secondsand from 1000 to1500secondsupon filler addition, after which the gel strength was evaluated which showed an increase upon addition of filler and cross-linker.In addition, the swelling rate, capacity and retardation time have been measured to model hydrogel behavior and examine the expansion resistance as well as permeation resistance, which presented that swelling rate and capacity has a decline with adding filler.

Keywords:

polysodiumacrylate , Gel point , Hydrogel , Winter-Chamon , viscosity