Polymorphism-controlled Young’s modulus of biobased polymers: Time-dependence due to physical aging

半结晶聚合物的杨氏模量取决于晶体和非晶结构的结构和形态。虽然在该项目的第一部分中选择的生物聚合物的晶体多态性对杨氏模量的影响已经量化，表明较低的模量较低的有序和较低密度的晶相，第二个项目部分的重点是由于老化的机械行为的时间依赖性。主要目的是分析与玻璃弛豫和后结晶有关的物理老化引起的半结晶生物聚合物的选定机械性能的时间依赖性。其目标是确定（初级）结晶相关的结构参数，最大限度地减少或提高长期的性能变化。在这些结构参数中，考虑了结晶度、特定晶体多晶型物的优势或包括晶体与非晶周围之间的界面结构的晶体形态。这些参数对非晶相施加了不同的约束，改变了玻璃弛豫行为（在玻璃态下有效）和在初级结晶期间生长的晶体之间的非晶区域中的结晶后特性（主要在高于玻璃化转变温度的温度下有效）。对选定的聚合物进行化学老化（叠加在物理老化上）的可能影响评价。该研究将导致半结晶聚合物的物理老化的更好的理解，特别是通过识别的多态性和晶体形态相关的参数的结构。随着对环境友好的生物来源和/或可生物降解的聚合物的重视，强烈考虑进一步建立具有长寿命的生态中性材料的重要需求。

Young’s modulus of semicrystalline polymers depends on the structure and morphology of both crystals and amorphous structure. While for selected biopolymers in the first part of the project the effect of crystal polymorphism on Young’s modulus has been quantified, suggesting a lower modulus for less ordered and less dense crystal phases, focus of the second project part is the time dependence of the mechanical behavior due to aging. Main objective is the analysis of the time dependence of selected mechanical properties of semicrystalline biopolymers caused by physical aging related to glass relaxation and post-crystallization. It is the goal to identify (primary)-crystallization-related structural parameters which minimize or enhance long-term change of properties. Among these structural parameters, the crystallinity, the pre-dominance of specific crystal polymorphs, or the crystal morphology including the interface-structure between crystals and amorphous surrounding are considered. These parameters impose different constraints to the amorphous phase, changing the glass-relaxation behavior (effective in the glassy state) and post-crystallization characteristics in amorphous regions between crystals grown during primary crystallization (mainly effective at temperatures above the glass transition temperature). A possible influence of chemical aging, which is superimposed on physical aging, is to be evaluated on selected polymers. The research will lead to an improved understanding of physical aging of semicrystalline polymers, in particular by identification of polymorphism- and crystal-morphology-related parameters of the structure. With the emphasis placed on environment-friendly bio-sourced and/or biodegradable polymers, the important demand for further establishment of ecologically neutral materials with a long lifetime is strongly considered.