Preparation and characterization of hydrogel nanocomposite based on nanocellulose and acrylic acid in the presence of urea

In this study, acrylic acid (AA) and cellulose nanofibers (CNFs) were used as main materials to synthesize an acrylic-nanocellulose hybrid hydrogel nanocomposite in the presence of urea. The interpenetrating polymer networks were obtained by radical polymerization in different urea: AA ratios (0:10, 1:10, 3:10, 5:10, 10:10). Fourier transform infrared spectroscopy (FTIR) combined with X-ray diffraction (XRD) and elemental analysis techniques confirmed the chemical interaction of urea in the network structure. Free absorption and water absorption under load (AUL) of the synthesized hydrogels varying in urea: acrylic acid weight ratios were measured in distilled water and saline (0.9 wt%) solution for hybrid (5 wt% CNFs) and pure polyacrylic acid (0 wt% CNFs) hydrogels. It was found that incorporation of urea and CNFs in the hybrid structure generating compact hydrogel networks with high crosslink density leading to lower absorption with and without pressure, whereas incorporation of urea in the structure resulted in a more extended network with higher absorption capacity (about 3×) than hybrid structure.