Ultra small-angle X-ray scattering studies on structural changes in micrometers upon uniaxial stretching of segmented polyurethaneureas
Ultra small-angle X-ray scattering studies on structural changes in micrometers upon uniaxial stretching of segmented polyurethaneureas
复制标题
DOI：
10.1016/j.polymer.2008.12.050
复制
发表时间：
2009-03
期刊：
影响因子：
4.6
通讯作者：
S. Sakurai;H. Yoshida;F. Hashimoto;M. Shibaya;H. Ishihara;N. Yoshihara;S. Nishitsuji;M. Takenaka
中科院分区：
文献类型：
--
作者：
S. Sakurai;H. Yoshida;F. Hashimoto;M. Shibaya;H. Ishihara;N. Yoshihara;S. Nishitsuji;M. Takenaka
采用超小角x射线散射（USAXS）实验研究了室温下单轴拉伸弹性体分段聚氨酯的微观结构变化。可以将样品膜拉伸至α=7.5而不断裂，其中α表示拉伸比。在α=6.5左右，样品变得浑浊，而当去除应力时，样品恢复透明。为了理解这种奇怪的现象，我们进行了USAXS实验，以微米为单位进行结构分析。虽然当样品变得浑浊（α=7.2左右）时，平行于拉伸方向（SD）出现了一组条纹，但更有趣的结果是，在α=5.0左右，垂直于SD方向出现的一组条纹要早得多。通过对散射强度谱的仔细观察，发现了多个干涉峰的演化，这可以归因于片层状颗粒的形状因素。由于条带在去除应力后消失，“层状颗粒”被认为是裂纹，在后续阶段进一步发展为裂纹。USAXS测量结果表明，在α=5.0附近出现平行于SD方向的片状裂纹，进一步拉伸形成了平行于SD方向的片状裂纹，并与之前的平行裂纹共存。
Ultra small-angle X-ray scattering (USAXS) experiments were conducted in order to examine structural changes in micrometers upon uniaxial stretching of elastomeric segmented polyurethaneureas at room temperature. It was possible to stretch the sample film up to α=7.5 without break, where α designates the stretching ratio. Around α=6.5 the sample became turbid, while it recovered transparency when the stress was removed. To understand this curious phenomenon, we conducted the USAXS experiments for the structural analyses in micrometers. Although a set of streaks appeared in the direction parallel to the stretching direction (SD) when the sample became turbid (around α=7.2), more interesting result is that a set of streaks appeared in the direction perpendicular to SD much earlier around α=5.0. Close examination of the scattering intensity profile revealed evolution of multiple interference peaks, which could be ascribed to the form factor of a lamellar particle. Since the streaks disappeared upon the removal of the stress, “lamellar particles” are considered to be crazes, which develop further into cracks in a subsequent stage. From the results of USAXS measurements, it is suggested that the lamellar-shaped crazes appeared around α=5.0 being oriented parallel to SD, and further stretching created other lamellar-shaped crazes being oriented perpendicular to SD, which are co-existing with the preceding parallel crazes.