Effect of Crosslinking Agent Concentration on Swelling Behavior of Acrylic-Nanocellulose Hydrogels

In this study, composite hydrogels with interpenetrated polymer networks (IPNs) based on cellulose nanofibrils (CNFs) and poly(acrylic acid) comprising low amount of CNFs were synthesized through radical polymerization for agricultural applications. N,N′-Methylene-bis-acrylamide (MBA) was used as crosslinking agent. The formation of this IPN structure was studied with thermogravimetric analysis (TGA). The onset of PAA dehydroxylation began at higher temperature in the presence of cellulose nanofibrils. The MBA concentrations of 0.05, 0.1, 0.2, 0.3, and 0.4 wt% were used to investigate its influence on the swelling degree and strength of the samples. The absorption capacities measured in distilled, drinking and saline (0.9%) water showed an increase upon increasing crosslinking agent concentration. Absorptions under load (AUL) data presented higher strength (ranged from 17 g/g to 21 g/g) with increasing the network crosslink density up to 0.3 wt% MBA concentration. The absorption rate data also followed the same trend as AUL data.