中文摘要：

单轴拉伸等规聚丙烯高度取向的α晶,材料表现出负泊松比,材料拉伸胀大.广角和小角X射线散射原位跟踪拉伸过程中子晶和母晶的相对转动,同时伴随着样品宽度的增加.等规聚丙烯独特的子母晶结构,符合胀大材料的基本要求.在拉伸过程中,子晶和母晶之间的夹角由最初的80°或者100°转动成90°,导致了样品的宽度的增加.实验结果表明可以利用微观尺度上特殊的晶体形态,设计胀大材料.

英文摘要：

Auxetic behavior with negative Poisson＇s ratio was observed during a uniaxial tensile test on isotactic polypropylene （iPP） with highly oriented α crystal. In situ wide angle and small angle X-ray scattering measurements revealed that a relative rotation of parent and daughter lamellae was accompanied with the expansion of sample width. The parent and daughter lamellae structure matches the essential requirement of auxetic materials. During the tensile test,the angle between parent and daughter lamellae rotates from initial 80° or 100° to close to 90°,which well accounts for the lateral expansion of the samples. The results demonstrate a new mechanism based on special crystallography to design auxetic materials on a mesoscopic scale.