The Modification Of Cellulose And Its Applications On Food Packaging

Food packaging materials are mainly used for packing vegetables, fruits, drinks, etc. To keep the food in the production, processing, storage, transportation and sales of each link of freshness, from the effects of biological, microbiological or external environment, slow food quality and the quality of the recession, the maximum keep food original color, aroma and taste. Hydrophobic packaging material is nearly 20 years developed a kind of new packaging materials. Will be able to restrain or kill microbes, reduce environmental microbe in food, improve safety and prolong the shelf life of food, is a kind of potential new packaging material. This thesis mainly studied the effect of hydrophobic groups on the chemical modification of cellulose, and it would provide theoretical guidance to the actual production of the food packaging materials.In this thesis, the effect of degree of substitution (DS) on the hydrophobicity of acetylated cellulose was studied using liquid marbles. Acetylated cellulose powders with varying DS were prepared by reacting cellulose with acetic anhydride. The surface energy of the acetylated cellulose decreases with increasing DS, and for DS of 0.39, the acetylated cellulose was able to encapsulate a water droplet to form a liquid marble. The corresponding cellulose acetate powder-over-water spreading coefficient was ca.8.9. Increasing DS also improved the mechanical stability of the liquid marble. This opens important perspectives for the precise control of DS of cellulose acetate for various practical applications in membranes, filters, scaffolds, and textiles.Paper optimized the acetylation of cellulose membrane preparation technology, studied the hydrophobic cellulose membrane performance and mechanical performance. Results showed that the substitution degree is 2.50, the optimal concentration of 7.5% was prepared film performance:film thickness is 200 μm, tensile strength is 6.5 MPa, the elongation at break 32%, moisture absorption rate of 17% and moisture permeability of 1.4×10-7 g/(m·s·Pa), through oil rate for 6 g-mm/(m2-d). By comparison, the acetylation of cellulose membrane hydrophobic properties and mechanical properties are better than the original cellulose membrane performance.Paper optimized the preparation methods of hydrophobic food wrapping paper. Using wet end to add blown film, paper and surface spray method of the preparation of food wrapping paper, three methods to study the hydrophobic properties of the wrapping paper (contact angle and COBB value), mechanical properties (tensile strength and elongation at break). The results showed that the wet end add of the hydrophobic properties and mechanical properties of paper were no significant changes; Paper scraping the membrane of the hydrophobic properties and mechanical properties of paper have good improvement, COBB value is 13.4 g/m2, contact angle is 117.2°, the tensile strength of 1.08 kN/m2, elongation at break of 5.6%; Surface spray of the hydrophobic properties and mechanical properties of paper also to have certain to improve, COBB value is 15.6 g/m2, contact angle is 108.9°, the tensile strength of 0.93 kN/m2, elongation at break up to 6.2%. As a result, the final choice using acetyl content is 39.8% of cellulose acetate 5% concentration of paper membrane preparation food wrappers.