Tailoring of polyesters for bead foams with enhanced thermal resistivity and investigation of structure-property-relationships during expansion and fusion

拟议项目的主要目标是科学地解释和了解工程聚合物聚对苯二甲酸丁二醇酯(PBT)的珠状泡沫在膨胀和熔化过程中发生的复杂影响。这些PBT微珠泡沫(E-PBT)是新开发的，与已有的聚苯乙烯微珠泡沫(EPS，约.80°C)和聚丙烯(EPP，约110°C)。目前，只有使用环氧扩链剂(CE)才能使E-PBT具有良好的发泡性能和均匀的形貌和焊接。然而，这种CE会引起聚合物链的变化，从而导致不同的流变行为导致不同的膨胀。由于CE的复杂反应，到目前为止，还不可能解释E-PBT的焊接行为。到目前为止，还没有发现分子结构与发泡/焊接行为更深层次的关联。因此，PBT具有系统变化的结构(线性、支化、交联化等)。将制作并研究它们的流变行为(拉伸、剪切和熔体强度)。将首先在实验室规模上用高压灭菌器进行发泡，以确定其膨胀行为。基于这些结果，最有希望的体系将被更大规模地微珠发泡。E-PBT的熔融与已有的珠状泡沫塑料有很大的不同，目前还不清楚。在这里，主要的焦点将是表面调查，以解释在蒸汽箱成型机熔化过程中的影响。通过对聚合物进行改性，从而对珠子表面进行改性，将有可能影响焊接性能。

The main goal of the proposed project is to scientifically explain and understand the complex effects that are happening during the expansion and fusion of bead foams from the engineering polymer polybutylene terephthalate (PBT). These PBT bead foams (E-PBT) are newly developed and possess a higher heat stability compared to the established bead foams from polystyrene (EPS, approx. 80 °C) and polypropylene (EPP, approx. 110 °C). A good foaming with an even morphology and welding of E-PBT is currently only possible with an epoxy chain extender (CE). However, this CE induces changes in the polymer chains and thereby also the rheological behavior is different leading to different expansion. By now, it is not possible to explain the welding behavior of E-PBT due to the complex reactions of the CE. So far, no deeper correlation of the molecular structure and the foaming/welding behavior was found. Therefore, PBT with systematically varied structures (linear, branched, cross-linked etc.) will be made and investigated regarding their rheological behavior (elongational, shear and melt strength). Foaming will be carried out firstly in a lab scale with an autoclave to determine the expansion behavior. Based on these result the most promising systems will be bead foamed on a larger scale. The fusion of E-PBT differs significantly from the established bead foams and is yet not understood. Here, the main focus will be the surface investigation to explain the effects during the fusion in the steam chest moulding machine. By modifying the polymer and consequently the beads surface it would be possible to influence the welding performance.