Preparation And Characterization Of Sericin-based Superabsorbant Composite Material

Present widely-used polyacrylic acid polymer, a kind of superabsorbent polymer (SAP), performs badly on biodegradation, which do harms to cause ecological environment and whose raw material is derived from increasingly exhausted oil. Therefore, researches on biodegradable SAP are of great importance to reducing environmental pollution.Sericin, a natural polymer, is generally treated as waste in silk prodction. If sericin is recycled and utilized as biological resources, there woulid be considerable social and economic benefits. Amino acids in sericin, which contain abundance polar groups (-OH,-COOH,-NH2etc), have good property in hydropgily, reactivity and biodegradability. The application of sericin to absorbent material field, and graft copolymerization of sericin and propenyl monomer to develop biodegradable SAP, can enrich the types of SAP and offer a new way to expand the utilization of sericin.Taken sericin as material, acrylic acid (AA) and acrylamide (AM) as monomer, ammonium persulfate (APS) and Methylene bisacrylamid (MBA) as initiator and crosslinker, this research synthesized a biodegradable SAP—Sericin/PAA-AM by polymerization in aqueous solutin. In our work, the synthetic reaction condition was studied including the dosage of sericin, the ratio of monomers, dosage of crosslinker and initiator, neutralization, temperture, and pH etc. After single factor experiment, orthogonal designed experiment of five factors, four levels was adopted to acquire optimal condition as follows:reaction temperture was60℃; reaction time was2h; the mass ratio of sericin to monomer wa1:2; the mass ratio of AA to AM was2:1; the mass ratio of initiator and crosslinker to monomer was2%and0.3%; neutralization degree was70%; pH was7. Water absorbencies of Sericin/PAA-AM in deionized water, tap water and0.9%NaCI solution were483g/g,296g/g and52g/g, respecyively. Consider inadequate absorption capacity of Sericin/PAA-AM SAP, sericin extracted by boiled-water was hydrolyzed by alkaline protease to different molecular weight of sericin, and the influence of processing conditions of enzymolysis modification was studied on sericin distribution of different molecular weight. It was found that the higher protease concertration, the smaller molecular weight of sericin would be. Furthermore, appropriate enzymolysis sericin was choosed and grafted with AA/AM to produce composite SAP with biodegradability. The differences was studied in structure and performance of this composite SAP, and mechanism of influence of different sericin structures was clarified on grafting percentage, water absorbency, water retaining capacity, biodegradability. The results showed that when the mass ratio of alkaline protease to sericin was5mg/g, APh-Sericin/PAA-AM’s capacity reached the highest value, including grafting percentage, water absorbency, retaining capacity and biodegradability. The water absorbency of lyophilized Sericin/PAA-AM was896g/g in deionized water,424g/g in tap water, and83g/g in0.9%NaCl solution.This research could offer a reference for sericin-based ecological and functional materials.