Preparation And Properties Of Modified Cellulose Derivatives Coating Materials Of Slow-release Fertilizers

Cellulose is natural polymer that is abundantly available from many renewable plant sources. Its derivatives are nontoxic, biodegradable and possess good film forming property. Cellulose derivatives are widely used in biology, food, medicine and other fields. Using cellulose derivatives as slow-release fertilizer coating materials not only reduce the nutrient release rate, but also can be decomposed in soil. The coating materials with different permeability can be prepared using different cellulose derivatives. These materials can meet the different demand of nutrients of different crops in their different growth cycles.Carboxymethyl cellulose can solute in water and ethyl cellulose has strong hydrophobicity. These characters limit their application in coating material. In this paper, three kinds of slow-release fertilizer coating materials were prepared by hydrophobic or hydrophilic modifications. This paper mainly discussed the structure and the performance of all the films including hydrophobic/hydrophilic character,crystallinity, thermal stability and urea permeability.(1) A series of crosslinked carboxymethyl cellulose films were prepared using formaldehyde as the crosslinking agent, ammonium chloride as the acidity regulator for the reaction system, 1,2- propylene carbonate (PC) as the plasticizer. The results show that the content of ammonium chloride is 15% of the formaldehyde and 1,2-propylene carbonate is 8% of the solid content within film. The hydrophobicity is increased and the water absorption, crystallinity and accumulated permeation amount of urea is decreased following the increase of the content of formaldehyde.(2) Ethyl cellulose monoester of maleic acid was synthesized using acetic acid as solvent, anhydrous sodium acetate as catalyst. Modified ethyl cellulose films were preparation using acetone as solvent. The structure of product and the effect of the degree of substitution were studied. The performance of the modified film was analyzed. The structure was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance. The optimal experimental conditions were as follows: the molar ratio of the hydroxyl content of ethyl cellulose to maleic anhydride 1:4, reaction temperature 95 ℃,reaction time 6 h. In these conditions,the product’s degree of substitution is higher. The hydrophilicity of the film is enhanced, but the accumulated permeation amount of urea is little.(3) Ethyl cellulose/chitosan film was prepared by mixing ethyl cellulose solution and chitosan solution. Glyceryl triacetate was used as plasticizer. The optimized preparation conditions, the structure and performance of composite film were studied.The results indicated that the mixing temperature was 15 ℃ and the volume ratio of ethyl cellulose solution to chitosan solution is less than 20:3. Fourier transform infrared spectroscopy and X-ray diffraction shows that there is interaction between ethyl cellulose and chitosan. With the increasing content of chitosan, the hydrophilicity is enhanced, and the accumulated permeation amount of urea is increased.