Gelatin-G-Poly(Sodium Acrylate-co-Acrylamide)/Kaolin Superabsorbent Hydrogel Composites: Synthesis, Characterisation and Swelling Behaviour
A novel superabsorbent hydrogel composite based on gelatin has been prepared by graft copolymerisation of acrylic acid and acrylamide in the presence of kaolin powder, using methylene-bisacrylamide (MBA) as a crosslinking agent and ammonium persulfate as an initiator. The synthetic variables affecting the water absorbency of the resulting superabsorbent composite were studied and the composite structure was confirmed using FT-IR spectroscopy. A new absorption band at 1728 cm−1 in the composite spectrum confirmed the presence of a kaolin-organic polymer linkage. The effect of kaolin content and MBA concentration showed that increasing these parameters decreased the water absorbency of the superabsorbent composite. The swelling measurements were conducted in aqueous salt solutions. Results indicated that the swelling ratios decreased with an increase in the ionic strength of the salt solutions. The pH of the various solutions also affected the swelling of the superabsorbent. Finally, the swelling kinetics of synthesised composites with various absorbent particle sizes was briefly examined.