Thermoplastic starch modified during melt processing with organic acids: The effect of molar mass on thermal and mechanical properties

被引:70
作者
Da Roz, Alessandra L. [2 ]
Zambon, Marcia D. [3 ]
Curvelo, Antonio A. S. [3 ]
Carvalho, Antonio J. F. [1 ]
机构
[1] Univ Sao Paulo, Dept Mat Engn, BR-13566590 Sao Carlos, SP, Brazil
[2] Univ Fed Sao Carlos, BR-18052780 Sorocaba, SP, Brazil
[3] Univ Sao Paulo, Dept Chem Phys, BR-13566590 Sao Carlos, SP, Brazil
基金
巴西圣保罗研究基金会;
关键词
Thermoplastic starch; Carboxylic acids; Dynamic mechanical properties; CITRIC-ACID;
D O I
10.1016/j.indcrop.2010.09.015
中图分类号
S2 [农业工程];
学科分类号
0828 ;
摘要
Thermoplastic starch (TPS) was modified with ascorbic acid and citric acid by melt processing of native starch with glycerol as plasticizer in an intensive batch mixer at 160 degrees C. It was found that the molar mass decreases with acid content and processing time causing the reduction in melting temperature (T-m). As observed by the results of X-ray diffraction and DSC measurements, crystallinity was not changed by the reaction with organic acids. T-m depression with falling molar mass was interpreted on the basis of the effect of concentration of end-chain units, which act as diluents. FTIR did not show any appreciable change in starch chemical compositions, leading to the conclusion that the main changes observed were produced by the variation in molar mass of the material. We demonstrated that it is possible to decrease melt viscosity without the need for more plasticizer thus avoiding side-effects such as an increase in water affinity or relevant changes in the dynamic mechanical properties. (C) 2010 Elsevier B.V. All rights reserved.
引用
收藏
页码:152 / 157
页数:6
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