In this work, the lamellar structural evolution and microvoids variations of β polypropylene (β-PP) during the processing of two different stretching methods, sequential biaxial stretching and simultaneous biaxial stretching, were investigated in detail. It was found that different stretching methods led to significantly different lamellae deformation modes, and the microporous membranes obtained from the simultaneous biaxial stretching exhibited better mechanical properties. For the sequential biaxial stretching, abundant coarse fibers originated from the tight accumulation of the lamellae parallel to the longitudinal stretching direction, whereas the lamellae perpendicular to the stretching direction were easily deformed and separated. Those coarse fibers were difficult to be separated to form micropores during the subsequent transverse stretching process, resulting in a poor micropores distribution. However, for the simultaneous biaxial stretching, the β crystal had the same deformation mode, that is, the lamellae distributed in different directions were all destroyed, forming abundant microvoids and little coarse fibers.

在这项工作中，β聚丙烯的层状结构演变和微孔变化（β-PP）在两种不同拉伸方法的加工过程中进行了详细研究：顺序双轴拉伸和同时双轴拉伸。发现不同的拉伸方法导致薄片变形模式显着不同，并且通过同时双轴拉伸获得的微孔膜表现出更好的机械性能。对于顺序双轴拉伸，大量的粗纤维源自平行于纵向拉伸方向的薄片的紧密堆积，而垂直于拉伸方向的薄片容易变形和分离。这些粗纤维在随后的横向拉伸过程中难以分离形成微孔，导致微孔分布差。然而，β晶体具有相同的变形模式，即破坏了沿不同方向分布的薄片，形成了丰富的微孔，几乎没有粗纤维。