Polymer foams with gradient cellular structure show superior mechanical and physical properties, while developing polymer foams with tailored gradient-structures is still challenging. Herein, an environmentally-friendly foaming process with CO₂ as blowing agents was developed for fabricating structure-gradient thermoplastic polyurethane (TPU) foams. In the unique microcellular foaming process, a two-step sorption procedure with a low CO₂ pressure at the first stage and a high CO₂ pressure at the second stage was used to generate gradient CO₂ concentration in the solid TPU samples, which results in gradient cellular morphology in TPU foams. By varying the second sorption time, TPU foams with various gradient cellular morphology were prepared. Interestingly, the gradient cellular morphology helped to increase compression strength by 71.4% and modulus by 113.8%, to enhance resilience with a 24.7% reduction in energy loss coefficient and a rebound coefficient of 61.4%, and also to benefit shape-recovery after long compression deformation.

具有梯度蜂窝结构的聚合物泡沫具有优异的机械和物理性能，而开发具有定制梯度结构的聚合物泡沫仍然具有挑战性。_{在此，开发了一种以CO 2}作为发泡剂的环保发泡工艺，用于制造结构梯度热塑性聚氨酯（TPU）泡沫。_{在独特的微孔发泡工艺中，采用第一阶段低 CO 2}压力和第二阶段高 CO ₂压力的两步吸附过程产生梯度 CO ₂固体 TPU 样品中的浓度，这导致 TPU 泡沫中的梯度细胞形态。通过改变第二次吸附时间，制备了具有不同梯度蜂窝形态的 TPU 泡沫。有趣的是，梯度细胞形态有助于增加 71.4% 的压缩强度和 113.8% 的模量，以增强弹性，降低 24.7% 的能量损失系数和 61.4% 的回弹系数，并有利于长时间压缩后的形状恢复形变。