Abstract
Poly(N-vinyl formamide-co-acrylamide) hydrogels were prepared by free radical chain polymerization using ammonium persulfate as redox initiator, N,N-Methylene bisacrylamide as crosslinker, and N, N', N'', N'''-tetramethyl ethylenediamine as accelerator. The synthesis of hydrogels was confirmed by FTIR and SEM. The effect of compositional change and temperature on the mechanical and rheological behavior was explored in detail. Different rheological tests (flow curve, frequency sweep, creep recovery, and hysteresis loop) were conducted to study the effect of temperature (25-40 degrees C), compositional change, and N-vinyl formamide concentration on the viscoelastic thixotropic behavior of copolymer hydrogels. Different rheological models (Bingham, modified Bingham, and Ostwald power law) were applied to check the pseudo plastic shear thinning non-Newtonian behavior, as confirmed by decline in viscosity with shear rate. Highly rough and microporous morphology, high thixotropy (hysteresis loop area of 4498.5 Pa-s(-1) obtained from the hysteresis loop test), and better recovery percentage (95% form creep recovery) were observed for hydrogels having increased N-vinyl formamide (NVF) concentration. The obtained results showed an increase in mechanical strength with increasing NVF concentration in the hydrogels and their valuable applications for wastewater treatment, drugs delivery, cosmetics and so on.
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