Strain steps are applied to elastomers in a pneumatic relaxometer and monitored by small‐angle X‐ray scattering (SAXS). The relaxometer provides a rise time of 13 ms for strain pulses of step height Δε = ±1 in strain. The basic character of the 2D SAXS frames is examined and corresponding invariants Q(t) are analyzed. Three thermoplastic polyurethanes (TPU) of hardness 85 Shore A with different soft segments are studied both unannealed and annealed. The first response of all materials is a fast morphology conversion which finishes within t_mc =250 ms. Because it has been untraceable, it is characterized by a settling stroke Q(t_mc) − Q(0). The second response is a slow morphology adjustment process which complies with logarithmic relaxation. It is characterized by a relaxation rate D_Q = Q(10 t)/Q(t) − 1. Comparison indicates that the nanoscopic morphology relaxation processes appear to have little direct relation to the macroscopic stress relaxation curves. The materials differ with respect to hard‐domain morphology stability and morphology recovery. Most unstable is the morphology of the annealed polyether‐based material. It forms nanofibrillary entities when strained.

中文翻译：

---

快速应变步骤后热塑性聚氨酯弹性体的短期形态松弛

应变步骤在气动张弛仪中应用于弹性体，并通过小角度X射线散射（SAXS）进行监控。对于应变中步长为Δε=±1的应变脉冲，张弛仪提供13 ms的上升时间。检查了二维SAXS帧的基本特征，并分析了相应的不变量Q（t）。分别对未经退火和退火的三种硬度为85 Shore A的热塑性聚氨酯（TPU）进行了研究。所有材料的第一个响应是快速的形态转换，在t _mc  = 250 ms内完成。因为它是无法追踪的，所以它的特征是稳定行程Q（t _mc）− Q（0）。第二个响应是符合对数弛豫的缓慢的形态调整过程。它的特征在于松弛率D _Q  = Q（10  t）/ Q（t）−1。比较表明，纳米形态松弛过程似乎与宏观应力松弛曲线几乎没有直接关系。这些材料在硬域形态稳定性和形态恢复方面有所不同。最不稳定的是退火的聚醚基材料的形态。当拉紧时，它形成纳米原纤维实体。