Research On The Modified-corn Stalk/PVP Semi-IPN Superabsorbents

Acrylic acid modified-corn stalk/PVP semi-IPN superabsorbents were prepared by graft copolymerization of acrylamide?AM?and acrylic acid?AA?with acrylic acid-modified corn stalk in an aqueous solution,using corn stalk as raw material,ammonium persulfate and sodium bisulfite as redox initiators and polyethylene glycol diacrylate as crosslinker.Factors affecting water absorbency,fertilizer solution absorbency,water retention and gel strength of the modified corn stalk/PVP semi-IPN superabsorbents,such as amount of acrylic acid modified-corn stalks,AA/AM mass ratio,AA neutralization degree,crosslinker amount,PVP amount and initiator amount,etc,were investigated.Morphologies,structure and thermal properties of the modified corn stalk/PVP semi-IPN superabsorbents were characterized by FTIR,XRD,optical microscope and TGA.Acrylic acid-modified-corn stalk/PVP semi-IPN superabsorbents,having good water absorbency,water retention,fertilizer solution absorbency,fertilizer keeping ability,heat properties and gel strength,have been synthesized.The main research findings are as follows.1.With the increase of acrylic acid-modified-corn stalk amount,water absorbency rate and water equilibrium absorbency of the modified corn stalk/PVP semi-IPN superabsorbents decreased steadily,while water retention and gel strength of the modified corn stalk/PVP semi-IPN superabsorbents increased gradually.When the modified corn stalk amount was 50%,the modified corn stalk/PVP semi-IPN superabsorbents still had water absorbency as high as 322g/g,accompanied with the gel strength of 18.3Pa.s.2.With the increase of acrylic acid/acrylamide mass ratio,water absorbency,water retention,fertilizer solution absorbency and gel strength of modified corn stalk/PVP semi-IPN superabsorbents increased firstly and then decreased.When acrylic acid/acrylamide mass ratio was 60:40,the properties of the modified corn stalk/PVP semi-IPN superabsorbents,such as water absorbency,urea solution absorbency,KCl solution absorbency,NH₄H₂PO₄ solution absorbency and gel strength reached the maxima with 1238g/g,977g/g,56g/g,50g/g and12Pa.s,respectively.3.With the increase of ammonium persulfate amount,water absorbency,water retention,fertilizer solution absorbency and gel strength of the modified corn stalk/PVP semi-IPN superabsorbents increased firstly and then decreased.When ammonium persulfate amount was 1.6%,the properties of the modified corn stalk/PVP semi-IPN superabsorbents,such as water absorbency,urea solution absorbency,KCl solution absorbency,NH₄H₂PO₄ solution absorbency and gel strength were 921g/g?685g/g,52g/g,48g/g and 11.5Pa.s,respectively.4.With the increase of crosslinker amount,water absorbency and fertilizer solution absorbency of the modified corn stalk/PVP semi-IPN superabsorbents increased firstly and then decreased,while water retention and gel strength increased steadily.When crosslinker amount was 0.3%,the properties of the modified corn stalk/PVP semi-IPN superabsorbents,such as water absorbency,urea solution absorbency,KCl solution absorbency,NH₄H₂PO₄ solution absorbency and gel strength were 931g/g,708g/g,54g/g,49g/g and 10.8Pa.s,respectively.5.With the increase of acrylic acid neutralization,water absorbency,water retention,fertilizer solution absorbency and gel strength of the modified corn stalk/PVP semi-IPN superabsorbents increased firstly and then decreased,while water retention and gel strength increased steadily.When acrylic acid neutralization was70%,the properties of the modified corn stalk/PVP semi-IPN superabsorbents,such as water absorbency,urea solution absorbency,KCl solution absorbency,NH₄H₂PO₄solution absorbency and gel strength were 940g/g,727g/g,56g/g,51g/g and 11.8Pa.s,respectively.6.With the increase of PVP amount,water absorbency,water retention,fertilizer solution absorbency and gel strength of the modified corn stalk/PVP semi-IPN superabsorbents increased firstly and then decreased,while water retention and gel strength increased steadily.When PVP amount was 9%,the properties of the modified corn stalk/PVP semi-IPN superabsorbents,such as water absorbency,urea solution absorbency,KCl solution absorbency,NH₄H₂PO₄ solution absorbency and gel strength were 926g/g,705g/g,55g/g,49g/g and 10.8Pa.s,respectively.