화학공학소재연구정보센터
Polymer Engineering and Science, Vol.53, No.1, 134-145, 2013
Glycerol and esterified products of palmitic acid as a mixed plasticizer for thermoplastic tapioca starch
In this work, a mixture of glycerol (Gly) and derivatives of pentaerythritol or a,a'-diglycerol is used as a plasticizer for preparing a thermoplastic starch (TPS). A coplasticizer containing both hydroxyl group and a long aliphatic chain was synthesized by esterification reaction between pentaerythritol or a,a'-diglycerol and palmitoyl chloride in two different molar ratios, that is, 1:1 (PT1 and DG1), 1:2 (PT2 and DG2). The esterification products were characterized using Fourier transform infrared spectroscopy, 1H, and 13C nuclear magnetic resonance spectroscopy. The starch and the mixed plasticizer were blended in an internal mixer. The morphology and miscibility of the blends were investigated by scanning electron microscope. The mechanical properties, moisture adsorption, and retrogradation phenomenon of the TPS specimens were studied. The results indicated that the TPS specimen containing a mixed plasticizer in a weight ratio of 80% Gly: 20% PT1 showed the highest values of Young's modulus and tensile strength, because this mixed plasticizer system could form stronger hydrogen bonds with starch molecules. Moreover, thermoplastic starch with higher content of pentaerythritol or a,a'-diglycerol derivatives as a coplasticizer showed lower moisture adsorption, because its long aliphatic chain (hydrophobic part) of pentaerythritol derivatives may prevent starch molecules to reform hydrogen bonding and to recrystallize. POLYM. ENG. SCI., 2013. (c) 2012 Society of Plastics Engineers