蒙脱土对热塑性淀粉结晶和力学性能的影响

用熔融挤出方法制备的甘油塑化热塑性淀粉(GTPS)/蒙脱土(MMT)复合材料,可以有效抑制GTPS长时间放置的结晶行为,提高其力学性能。不同相对湿度下复合材料、GTPS、淀粉的X ray衍射说明,MMT对GTPS结晶有抑制作用;力学测试表明,随着w(MMT)=0%提高到30%,复合材料最大应力达到27 31MPa,应变从85 3%下降到17 8%,杨氏模量达到206 7MPa,断裂能从1 921N·m下降到1 723N·m。红外(FTIR)谱图显示复合材料中淀粉分子的碳氧(C—O)基团向高波数移动,蒙脱土中可反应性羟基(OH)向低波数移动。这表明蒙脱土分子可反应OH和淀粉分子OH之间有氢键形成,使GTPS中淀粉分子之间氢键难以形成,蒙脱土在复合材料中起到阻隔剂的作用,是抑制GTPS结晶的主要原因;扫描电子显微镜(SEM)显示,蒙脱土均匀分散在GTPS中,提高了材料力学性能。

The Influence of Montmorillonite on Crystal and Mechanical Properties of Thermoplastic Starch

Glycerol-plasticized thermoplastic starch(GTPS)/montmorillonite(MMT) composites could effectively restrain the starch crystallization.These composites were prepared by the method of melting and extruding.The X-ray diffraction patterns of composites,GTPS and starch indicated that the introduction of MMT effectively restrained the crystallization of GTPS at different relative humidities.The mechanical testing of composites 〔w(MMT)=0%～30%〕 showed that the mechanical properties were obviously improved.The stress of composites reached 27.31 MPa,the strain decreased from 85.3% to 17.8%,Young′s modulus reached 206.7 MPa and the breaking energy decreased from 1.921 N·m to 1.723 N·m.FTIR spectroscopy revealed that the C—O groups of starch in composites moved to the higher wavenumber,while the reactive hydroxy group(OH) of MMT moved to the lower wavenumber.This indicated that the hydrogen bonds between the reactive OH group of MMT and the OH group of starch were formed,and the original hydrogen bonds between the starch molecules in GTPS were weakened.The hydrogen bonds between the reactive OH group of MMT and the OH group of starch played the main role of restraining the crystallization of GTPS.SEM revealed that MMT dispersed uniformly in GTPS and improved the mechanical properties of GTPS.