Study of different methods to induce crosslinking of polyacrylamide for agriculture process

The present study describes two different methods for the preparation of superabsorbent polyacrylamide (PAAm) hydrogels for application in farming of sandy soil. The two methods were employed to induce the crosslinking of the polymer matrix. In the first method a PAAm paste was exposed to gamma rays, while in the second method the polymer was thermally treated in the solid phase. Crosslinked PAAm hydrogel samples prepared by both methods were characterized by gel content, water absorbance, Fourier transform infrared (FTIR) spectroscopy, X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The parameters affecting the gel content, including the irradiation dose and temperature, were investigated. The obtained results suggested that the gel content of the PAAm hydrogel crosslinked by radiation and thermal treatments increases as the irradiation dose and temperature increased. Furthermore, the results indicated that the water absorbance reaches the maximum values at an irradiation dose of 30 kGy and a temperature of 120 ºC. SEM showed that the synthesized hydrogels have a porous morphology. The PAAm hydrogel samples were loaded with urea and their release behavior was examined in water. Finally, the effect of hydrogels on the growth of beans (Vicia faba L.) was studied. The radiation crosslinked samples displayed better stability during the farming period and enhanced plant growth in comparison with the samples crosslinked by thermal treatment.