Mechanical properties of semicrystalline polymers: Foundation in microscopic structure and molecular dynamics

半结晶聚合物的典型形态特征是由无序的无定形层分隔的薄层状晶体的纳米级两相结构。系链和缠结机械地连接相邻的晶体。晶体通常含有移动的构象缺陷，这使得晶体中的链具有一定的移动性。另一方面，半结晶聚合物的机械性能是复杂的，并且与半结晶形态密切相关。虽然结晶部分负责在小变形下的高刚度，但通常观察到对于中间变形和对于大变形应变硬化的塑性流动和原纤化，这是由结晶支架捕获的缠结网络引起的。基于半结晶形态的表征和理解以及上述晶内链动力学的最新进展，该项目的目的是找出形态和晶体结构之间的关系。链动力学和力学性能的定量方法。为此，我们结合联合收割机结构分析的X射线散射与机械变形实验在拉伸变形和压缩。对于具有不同结构和动力学特性的一些模型样品以及免费的普通商业材料，将通过应力松弛和蠕变实验来补充恒定速率下的变形。

The characteristic morphological feature of semicrystalline polymers is a nanoscopic two-phase structure of thin lamellar crystals separated by disordered amorphous layers. Tie chains and entanglements mechanically link neighboring crystals. The crystals often contain mobile conformational defects, which entail a certain mobility of the chains in the crystal. The mechanical properties of semicrystalline polymers on the other hand are complex and are intimately related to the semicrystalline morphology. While the crystalline fraction is responsible for the high stiffness at small deformation, plastic flow and fibrillation set in for intermediate deformation and for large deformation strain hardening is generally observed, caused by the entanglement network trapped by the crystalline scaffold. Building on recent progress in the characterization and understanding of the semicrystalline morphology as well as of the above mentioned intracrystalline chain dynamics, the aim of the project is to work out the relation between the morphology resp. the chain dynamics and the mechanical properties in a quantitative way. For this purpose, we combine structural analysis by X-ray scattering with mechanical deformation experiments in tensile deformation and under compression. Deformation at constant rates will be complemented by stress relaxation and creep experiments for a number of model samples with different structural and dynamics properties as well as for complimentary common commercial materials.