In this work the effects of testing temperature and drawing orientation on the fracture behaviour of biobased and biodegradable thermoplastic starch based films, currently applied in the food packaging field, were investigated. At this aim, the Essential Work of Fracture (EWF) approach was applied on samples tested at 0 °C, 25 °C and 50 °C both in machine (MD) and in cross (CD) directions. The specific essential work of fracture (w_e) values strongly decreased with the testing temperature, and w_e values of CD samples were systematically higher than those of the corresponding MD samples. Considering that photograms of the CD samples taken during the EWF tests highlighted that the yielding zone became progressively opaque as an effect of the strain induced crystallization, it was hypothesized that in CD specimens part of the tensile energy applied during the straining process was utilized for the orientation of the macromolecules along the strain direction, rather than for the propagation of the crack in the ligament zone. Tensile tests under quasi-static conditions on dumbbell specimens highlighted that, regardless to the drawing direction, the stiffness and the resistance at yield and at break decreased with the temperature, while the strain at break was considerably enhanced. Moreover, because of the strong anisotropy induced by the molecular orientation in the drawing direction, MD tested samples had higher elastic modulus, yield resistance, and stress at break compared to CD samples.

在这项工作中，研究了温度和拉伸方向对目前在食品包装领域中应用的生物基和可降解热塑性淀粉基薄膜断裂行为的影响。为此，将断裂的基本功（EWF）方法应用于在0℃，25℃和50℃下在机器（MD）和横向（CD）方向上测试的样品。特定的基本断裂功（w _e）值随测试温度而大大降低，而w _eCD样本的值在系统上高于相应MD样本的值。考虑到在EWF测试期间拍摄的CD样品的照相照片突出显示了屈服区由于应变诱导结晶的影响而逐渐变得不透明，因此可以假设在CD样品中，在拉伸过程中施加的部分拉伸能被用于拉伸。沿应变方向的大分子取向，而不是沿韧带区域的裂纹扩展。在准静态条件下对哑铃试样进行的拉伸试验表明，无论拉伸方向如何，其刚度和屈服强度和断裂强度都随温度而降低，而断裂应变则得到明显提高。此外，