Abstract：
In this study, a new system was developed to carry out simultaneous near-infrared (NIR) and small-angle X-ray scattering (SAXS) measurements. Aged polypropylene (PP) was examined with the NIR-SAXS system to demonstrate how it can be utilized to derive pertinent information about the polymer structure. Pairs of SAXS profiles and NIR spectra of PP in its initial state and after aging were measured to derive an in-depth understanding of the aging phenomenon. The SAXS profiles of the PP samples showed a clear shift of the SAXS peak to the lower q direction induced by the thermal aging, indicating an increase in the length of the long-period structure. Two-trace two-dimensional (2T2D) asynchronous correlation spectra derived from NIR spectra clearly revealed that the aging treatment leads to a substantial increase in the spectral intensity of the regularity bands representing the longer helix present in a folded lamellar structure. In other words, it suggests that the long helix structure is more abundantly present than the short helix structure in the aged PP than in the initial PP. By combining the information derived from the SAXS profiles and NIR spectra, the details of the aging-induced variation were clearly determined. Namely, aging causes additional crystallization of the PP by developing more helical structures, which involves an increase in the lamellar thickness as well as a decrease in the amorphous region. The growth of the rigid crystalline phase restricts the elastic deformation in the amorphous structure, which eventually induces the deterioration of PP by making the polymer hard but brittle. Such observation, in turn, implies that retarding or accelerating the crystallized structure of PP substantially works to control the progress of aging.
摘要：
在这项研究中,开发了一种新系统来同时进行近红外（NIR）和小角度X射线散射（SAXS）测量。用NIR-SAXS系统检查老化的PP，以证明如何利用它来获得有关聚合物结构的相关信息。测量了PP在其初始状态和老化后的SAXS轮廓和NIR光谱对，以深入了解老化现象。PP样品的SAXS曲线显示了由热老化引起的SAXS峰向较低q方向的明显移动。表明长周期结构的长度增加。从NIR光谱得出的两道二维（2T2D）异步相关光谱清楚地表明，老化处理导致代表折叠层状结构中存在的更长螺旋的规则性带的光谱强度显着增加。换句话说,这表明，在老化的PP中，长螺旋结构比短螺旋结构更丰富。通过结合从SAXS轮廓和NIR光谱得出的信息，已清楚地确定了老化引起的变化的细节。即,老化通过发展更多的螺旋结构引起PP的额外结晶，这涉及层状厚度的增加以及非晶区域的减少。刚性结晶相的生长限制了非晶结构中的弹性变形，最终通过使聚合物变硬但变脆来诱导PP的劣化。这样的观察,反过来,这意味着延迟或加速PP的结晶结构基本上起到控制老化进程的作用。
