Research On The Preparation Of Lauric Acid-Starch Ester By Mechanical Activation And Its Properties

Using cassava starch as raw material, lauric acid as esterification agent and potassium carbonate as catalyst, Cassava Laurate Starch (CLS) was prepared by the technology of mechanical activation-solid phase. Based on the results of single factor experiment, response surface method was used to optimize the process of starch esterification. The effect of CLS on its molecular groups, crystal structure, thermal stability and morphology were investigated by Fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), thermal gravimetric analyzer (TG) and scanning electron microscopy (SEM). The Viscosity, Water absorbency of the CLS was also investigated. Based on the researches above, a kind of compound material was prepared with the CLS and Polyethylene as the raw material, Glycerol as plasticizer, the analysis of their mechanical properties would be theory basis for Starch’s depth development.1) The effects of reaction time, reaction temperature, the amount of catalyst and lauric acid were investigated respectively by using degree of substitution (DS) as evaluating parameter. The results indicated that under the following conditions can obtain better products:the time was60min, the temperature of ball milling was60℃, the amount percentage of Potassium carbonate was2.5%, the molar ratio of lauric acid and starch was0.3.2) Based on the results of single factor experiment, response surface method was used to optimize the process of Starch esterification. The optimum conditions were obtained as follows:the time was58min, the temperature of ball milling was61.0℃, the amount percentage of Potassium carbonate was 2.56%, the molar ratio of lauric acid and starch was0.56. DS could be obtained to0.0398.3) The effect of CLS on its molecular groups, crystal structure, thermal stability and morphology were investigated by Fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), thermal gravimetric analyzer (TG) and scanning electron microscopy (SEM). The Viscosity, Water absorbency of the CLS was also investigated. The analysis of infrared spectroscspy (IR) shows that lauric acid has reacted with starch, and the absorption peak of carboxyl increases as the DS of CLS increases. XRD analysis of CLS shows that the mechanical activation reaction can reduce the crystallinity of starch, making lauric acid easily to penetrate to the crystalline regions in the starch for reaction. TG analysis indicates that the thermal stability of CLS increase with the increase of DS. SEM study shows that in the preparation process of CLS, the starch receives the combined effects of mechanical activation and Esterification reaction, the Crystal structure was destroyed.4) The hydrophobicity increases as DS of CLS increases, and the viscosity decreases with increasing its DS. The main reason for that is the introduction of hydrophobic long chain fatty acid, hindering the association of hydrogen bonds between the starch molecules.5) The study on Composite material of CLS with PE found that the compatibility increases as DS of CLS increases, so that the tensile properties, thermal stability significantly improved.