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首页> 美国卫生研究院文献>Materials >Evaluation of the Zero Shear Viscosity the D-Content and Processing Conditions as Foam Relevant Parameters for Autoclave Foaming of Standard Polylactide (PLA)
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Evaluation of the Zero Shear Viscosity the D-Content and Processing Conditions as Foam Relevant Parameters for Autoclave Foaming of Standard Polylactide (PLA)

机译：零剪切粘度D含量和加工条件作为标准聚丙交酯（PLA）高压釜发泡的泡沫相关参数的评估

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In this comprehensive study, the influence of (i) material specific properties (e.g., molecular weight, zero shear viscosity, D-content) and (ii) process parameters (e.g., saturation temperature, -time, -pressure, and pressure drop rate) on the expansion behavior during the autoclave foaming process were investigated on linear Polylactide (PLA) grades, to identify and evaluate the foam relevant parameters. Its poor rheological behavior is often stated as a drawback of PLA, that limits its foamability. Therefore, nine PLA grades with different melt strength and zero shear viscosity were systematically chosen to identify whether these are the main factors governing the foam expansion and whether there is a critical value for these rheological parameters to be exceeded, to achieve low density foams with fine cells. With pressure drop induced batch foaming experiments, it could be shown that all of the investigated PLA grades could be foamed without the often used chemical modifications, although with different degrees of expansion. Interestingly, PLAs foaming behavior is rather complex and can be influenced by many other factors due to its special nature. A low molecular weight combined with a high ability to crystallize only lead to intermediate density reduction. In contrast, a higher molecular weight (i.e., increased zero shear viscosity) leads to significant increased expandability independent from the D-content. However, the D-content plays a crucial role in terms of foaming temperature and crystallization. Furthermore, the applied process parameters govern foam expansion, cell size and crystallization.
机译：在这项综合研究中，影响（i）材料的特定性能（例如分子量，零剪切粘度，D含量）和（ii）工艺参数（例如饱和温度，-时间，-压力和压降率）的影响）在线性聚丙交酯（PLA）牌号上研究了高压釜发泡过程中的膨胀行为，以识别和评估泡沫的相关参数。通常认为其流变性差是PLA的缺点，这限制了其起泡性。因此，系统地选择了九种具有不同熔体强度和零剪切粘度的PLA等级，以识别这些因素是否是控制泡沫膨胀的主要因素，以及是否存在超过这些流变参数的临界值，从而获得具有优良的低密度泡沫的产品。细胞。通过压降诱导的间歇发泡实验，可以证明所有研究的PLA牌号都可以发泡，而无需经常使用化学改性，尽管其膨胀程度不同。有趣的是，PLA的发泡行为相当复杂，由于其特殊性质，可能会受到许多其他因素的影响。低分子量与高结晶能力相结合仅导致中等密度降低。相反，较高的分子量（即增加的零剪切粘度）导致显着增加的可膨胀性，而与D含量无关。然而，就发泡温度和结晶而言，D含量起着至关重要的作用。此外，所施加的工艺参数控制泡沫的膨胀，泡孔尺寸和结晶。

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