The Development Of A Packaging Material With Antimicrobial Controlled Releasing

The dissertation is aimed to develop an active packaging material with antimicrobials released via a controlled manner through polymer surface modification process as well as the drug controlled releasing technology. The primary idea is composed of three parts as follows. Firstly, a thin layer of poly(acrylic acid) hydrogel is grafted onto the surface of low density linear polyethylene(PE) and poly(ethylene terephthlate)(PET) membranes by means of grafting polymerization surface modification process. At the same time, a pH-sensitive chitosan-based hydrogel microsphere with antimicrobial nisin encapsulated is prepared. Then the antimicrobial-loaded microspheres are immobilized onto the membrane surface through the attractive interaction between cations of chitosan-based hydrogel and anions of PAA hydrogel. Finally, the antimicrobial is released via the swelling and degradation of hydrogel.The surface modification of polymer membrane were carried out by hydroxylation through ammonium persulfate thermal-decomposition aqueously at 80℃and grafting using acrylic acid as monomer and cerium (IV) ions as redox initiator. The influence of hydroxylation time, acrylic acid concentration and grafting polymerization time on the packaging characteristics such as barrier properties, surface friction coefficient was also studied. The results show that: water vapour transmission rate is less influenced by such grafting process, while oxygen permeability of the film is sharply decreased with the concentration of surface carboxylic acid groups because of the increasing hydrogen-bonding strength under a dry state. Since the hydrophilic ability of the modified films is increased, contact angle are sharply decreased and friction coefficient are increased with the concentration of surface carboxylic acid groups.Simultaneously, a pH-sensitive chitosan-based hydogel was prepared using carboxyl terminated poly(ethylene glycol) as crosslinking agent through carbodiimide chemisty. The results show that the hydrogel has a low swelling ratio in neutral solution than that of in acidic or alkali ones. The main reason is that there exist some unreacted -NH2 and -COOH. Especially, the swellingratio of the sample in alkali solution is rather higher than that in acidic one. The reason is that the carboxylic acid groups have excessive molar ratio to amines in formula. Under the ideal condition, chitosan hydrogel can control the antimicrobial releasing speed with the change of pH environment.