Font Size: a A A

Synthesis And Properties Of Cationic Starch Based Amphoteric Semi-IPN Superabsorbent

Posted on:2009-11-17Degree:MasterType:Thesis
Country:ChinaCandidate:X LiFull Text:PDF
GTID:2121360245985894Subject:Applied Chemistry
Abstract/Summary:PDF Full Text Request
Superabsorbent is a new functional polymeric material, which can absorb a large amount of water while the water is hardly removed even under some pressure. Superabsorbent have been attracted considerable interest and research and were found many applications in agriculture, horticulture, feminine napkins, sanitation, medicine and soil for improvement. Swelling capacity, salt resistance and mechanical stress are more important consideration for the evaluation of superabsorbent. So many endeavors have made to improve these abilities of superabsorbent.Two kinds of amphoteric semi-interpenetrating polymer networks (semi-IPN) superabsorbent were prepared by a sequential-IPN method by graft copolymerization of acrylic acid onto cationic starch in mild aqueous media of poly(dimethyldiallylammonium chloride) (PDMDAAC) or poly(methacryloyloxyethyl trimethylammonium chloride) (PDMC) solution. The synthesis conditions were investigated systematically in term of the swelling of hydrogels, including the degree of substitution of starch, crosslinking content, initiator content, acrylic acid dose, PDMDAAC or PDMC dose and the neutralization of acrylic acid. It was observed that the salt resistance and mechanical stress of the superabsorbent are improved by introduction of PDMDAAC and PDMC to form semi-IPN structure superabsorbent. The swelling capacity in deionized water and 0.9 wt% NaCl of PDMDAAC superabsorbents achieved more than 1071 g/g and 94 g/g respectively, and PDMC superabsorbent achieved more than 1712 g/g and 111 g/g respectively. Meanwhile the amphoteric semi-IPN superabsorbent showed high swelling capacity in different pH solutions and different concentration of salt solutions. Besides, the superabsorbent showed good swelling reversibility.The semi-IPN structure were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and other techniques. The swelling capacity in different saline solutions and compressive stress of semi-IPN superabsorbent were investigated with grafted superabsorbent as controls. The results showed that the semi-IPN superabsorbent achieved a high compressive stress (1398 kg/m2) in higher water content (99.6%) while the grafted superabsorbent which the compressive stress only can achieve 986 kg/m2 in 99.4% water content.Considering the temperature varied with synthesis conditions, we monitored the temperature profiles during the polymerization process when some conditions were changed including polycation content, the molecular mass and the neutralization of acrylic acid. The amphoteric semi-IPN superabsorbents were also loaded with ammonium chloride as a model agrochemical and their potential for controlled release of ammonium chloride was judged by measuring conductivity. Various kinetic parameters such as the diffusion coefficient and swelling exponents were also calculated. The results showed that the amphoteric semi-IPN superabsorbent could absorb a certain amount ammonium chloride and their release results correlate well with the pH of the solution. Their release speed and release ratio in acid solution is better than in neutral and alkaline solution. The result of Semi-I and Semi-II show a promise in application for moisture and manure maintenance materials in agriculture/horticulture field.
Keywords/Search Tags:amphoteric semi-IPN superabsorbent, cationic starch, polycation, compressive stress, salt resistance, kinetics
PDF Full Text Request
Related items