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首页> 外文期刊>Journal of Applied Polymer Science >MECHANICAL PROPERTIES OF THERMOPLASTIC WAXY MAIZE STARCH
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MECHANICAL PROPERTIES OF THERMOPLASTIC WAXY MAIZE STARCH

机译：热塑性蜡质淀粉的力学性能

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The properties of thermoplastic amylopectin materials were investigated by stress-strain and relaxation measurements as a function of water content and crystallinity. Granular waxy maize starch was plasticized by extrusion with water and glycerol. The materials are amorphous after processing. The sharp fall in modulus at a water content of 10% is characteristic of a glass to rubber transition of an amorphous polymer. The materials are brittle below their glass transition temperature with a modulus of approximately 1000 MPa and an elongation of less than 20%. The amorphous rubbery materials are soft and weak with moduli of 0-10 MPa and tensile strengths of 0-2 MPa. The materials are viscoelastic, show plastic flow, and form a highly entangled polymer matrix, resulting in high values of elongation (500%), due to the high amylopectin molecular mass. Above glass transition temperature the amylopectin forms inter- and intramolecular double helices, crystallizing in a B-type crystal. The initial increase in modulus, tensile strength, and relaxation time is the result of the lower mobility of the amylopectin molecules and the reinforcement of the network by physical crosslinking. The drastic reduction of the elongation and the formation of cracks is the result of intramolecular crystallization. At crystalline junction zones the internal stress is increased and the interaction between molecules is reduced. (C) 1996 John Wiley & Sons, Inc. [References: 33]
机译：热塑性支链淀粉材料的性能通过应力应变和松弛测量作为含水量和结晶度的函数进行了研究。通过用水和甘油挤出将粒状蜡状玉米淀粉增塑。加工后的材料是无定形的。含水量为10％时模量的急剧下降是非晶态聚合物从玻璃到橡胶的转变的特征。这些材料在其玻璃化转变温度以下是脆性的，其模量约为1000 MPa，伸长率小于20％。非晶态橡胶状材料柔软而弱，模量为0-10 MPa，抗张强度为0-2 MPa。该材料是粘弹性的，具有塑性流动性，并形成高度纠缠的聚合物基体，由于支链淀粉的分子量较高，因此导致较高的伸长率值（500％）。高于玻璃化转变温度，支链淀粉形成分子间和分子内的双螺旋，在B型晶体中结晶。模量，拉伸强度和弛豫时间的最初增加是支链淀粉分子的较低迁移率和通过物理交联增强网络的结果。伸长率的急剧降低和裂纹的形成是分子内结晶的结果。在晶体结区，内部应力增加，分子之间的相互作用减小。 （C）1996 John Wiley＆Sons，Inc. [参考：33]

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