| High amylose-starch was easily made into film which had good transparency, high flexibility and high water tolerance. In addition, the films were nontoxic and non-pollution. The high amylose-starch was the best raw material to make the biodegradation film. The hydroxyls of PVA and amylose-starch formed hydrogen bonds, so the structure of the film was densification, which is beneficial to enhance mechanical property, heat stability and hydrolytic resistance of the film. The nano-TiO2 was added into the high polymer material, which was beneficial to enhance the property of basis material. In addition, the nano-TiO2 has photocatalytic effect which can give antibacterial function to composite. The film made from such composite had good antibacterial effect. In this paper, the raw material was the corn-starch which was hydrolyzed by pullulanase to obtain high amylose-starch. It was mixed with PVA and nano-TiO2 to make the antibacterial film by tape-casting. The main conclusions were as follows:1. Preparation and characterization of high amylose-starchThe optimal technological conditions of hydrolyzing corn-starch by pullulanase were as follows:the ratio of starch and water was 1/7; the temperature of hydrolysis was 60℃; the time of hydrolysis was 2h; the value of pH was 5.5; the dosage of pullulanase was 3 U/g. The content of amylose-starch was 57.098%.After hydrolyzing the corn starch, the content of amylose-starch and the initial pasting temperature of starch were enhanced.2. Study on disperity and antibacterial property of nano-TiO2The rutile TiO2 was obtained by hydrolyzing TiCl4. The anatase TiO2 was obtained from tetrabutyl titanate by sol-gel method. The crystal forms of TiO2 were good and pure.The optimal technological conditions of dispersing were as follows:the value of pH was 5; the content of namo-TiO2 was 1%; adding twain; the power and the time of ultrasonic were 600w and 30min. The particle size of TiO2 was about 100nm. Its specific surface area was 64m2/g. Its volume average particle size was 89nm.In the same conditions, the anatase TiO2’s ability of degradation of methylene blue was better than the rutile TiO2’s. The TiO2’s ability of degradation of methylene blue in ultraviolet region was better than in visible region.The anatase TiO2’s property of antibacterial was better than the rutile TiO2’s. The property of antibacterial to E.coil was better than to S.aureus. 3. Preparation of antibacterial amylose-starch film and study on its propertyThe amylose-starch film’s mechanical property and light transmittance were better than the corn-starch film’s. In the infrared spectrum, the peak of hydroxyl in 3500cm-1-3200cm-1 was getting wider.The particle size of number I nano-TiO2 was the smallest. It had the best compatibility with amylose-starch/PVA composite. The film with number I nano-TiO2 had the best flexibility, the highest transmittance. With a decrease in particle size of nano-TiO2 the water tolerance and the tensile strength of film increased, but elongation at break decreased. The smaller the particle size of nano-TiO2 was, the higher photocatalytic activity was, so the antibacterial property of film was the best.When the dosage of nano-TiO2 was 0.22g, the film had the best flexibility, the highest transmittance and the biggest tensile strength. With an increase in the dosage of nano-TiO2, the water tolerance and the antibacterial property of film increased, but elongation at break decreased.The ratio of anatase TiO2 and rutile TiO2 had small effect on the flexibility and uniformity of film, but it had big effect on the colour of film. With an increase in the content of anatase TiO2, the water tolerance, the transmittance and the tensile strength of film increased, but elongation at break decreased. When the ratio of anatase TiO2 and rutile TiO2 was 75/25, the antibacterial property of film was the best. |
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