Fabrication of PVA/Nanoclay Hydrogel Nanocomposites and Their Microstructural Effect on the Release Behavior of a Potassium Phosphate Fertilizer

Various PVA/nanoclay hydrogel nanocomposites with different weight fractions of nanoclay (0, 0.25, 0.5, 0.75 and 1) were prepared, characterized and their performances were investigated. The structures of the synthesized hydrogel nanocomposites and the samples loaded with a potassium phosphate fertilizer were proved by FTIR spectroscopy method. The interactions between the hydrogels and nanoclay and also the effect of fertilizer loading capacity on the nanocomposites were investigated using TGA method. TGA showed that the loading of the fertilizer decreased the hydrogel weight loss which was affected by the nanoclay weight percent. In addition, the effects of glutaraldehyde as crosslinking agent and incorporation of the nanoclay and fertilizer on the glass transition temperature of the prepared hydrogels were studied using DSC method. The Tg of the hydrogels increased by adding the nanoclay and decreased with the loading of the fertilizer. The SEM images showed that the microstructure and morphology of the hydrogel changed in the presence of the nanoclay and fertilizer. The increase of the nanoclay decreased the porosity of the hydrogel and made it denser. Furthermore, the EDX spectroscopy images of the samples proved the uniform dispersion of the fertilizer and nanoclay in the prepared hybrid hydrogels. The swelling of the hydrogels decreased with increasing of the nanoclay weight percent. The results showed that the swelling under load was the highest for the hydrogel nanocomposite with 0.5 wt% of the nanoclay. The increase of the nanoclay led to increasing of the physical networking that caused more desirable controlled release of the fertilizer.