Phase composition and molecular mobility in nylon 6 fibers as studied by proton NMR transverse magnetization relaxation
Phase composition and molecular mobility in nylon 6 fibers as studied by proton NMR transverse magnetization relaxation
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DOI：
10.1002/macp.200400089
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发表时间：
2004-08-30
影响因子：
2.5
通讯作者：
Penning, JP
中科院分区：
文献类型：
--
作者：
Litvinov, VM;Penning, JP
用H-1固体核磁共振横向磁化弛豫(T-2弛豫)谱研究了尼龙6纤维的相组成和分子迁移率。这项工作的目的之一是确定核磁共振弛豫法在准确测定尼龙6纤维结晶度方面的有用性。核磁共振弛豫结果用三相模型解释，该模型是基于晶相、半刚性晶体-非晶界面和软非晶相中链迁移率的明显差异而提出的。为了获得准确的物相组成数据，详细研究了纤维的吸水和高温退火对其相组成的影响。结果表明，水主要增塑非晶相的软部分。用实时核磁共振T2弛豫实验研究了纤维高温退火后的相组成和分子迁移率的变化。对未拉伸的低分子取向纤维，观察到最显著的退火效应(物相组成的变化)。对于卷绕速度较大的纤维，特别是高拉伸倍数的纤维，退火速度会变慢。纤维的加工条件，即缠绕速度和拉伸倍数，会影响不同相的相组成和分子迁移率。结果表明，核磁共振弛豫法为尼龙6纤维的相组成分析提供了一种快速、准确的方法。由核磁共振确定的刚性相的数量与用尼龙6纤维的传统方法得到的纤维的结晶度很好地一致，该方法结合了密度测量、广角X射线衍射和C-13核磁共振谱。因此，目前的核磁共振弛豫法大大简化了尼龙6纤维结晶度的测量。
The phase composition and molecular mobility of Nylon 6 fibers has been studied using H-1 solid-state NMR transverse magnetization relaxation (T-2 relaxation) spectroscopy. One of the objectives of this work is to determine the usefulness of the NMR relaxation method to accurately determine the crystallinity of Nylon 6 fibers. The NMR relaxation results have been interpreted using a three-phase model, which is proposed on the basis of distinct differences in chain mobility in the crystalline phase, the semi-rigid crystalamorphous interface, and the soft amorphous phase. In order to obtain accurate data on the phase composition, the effects of absorbed water and annealing of fibers at elevated temperatures were studied in detail. It was shown that water mainly plasticizes the soft fraction of the amorphous phase. Changes in the phase composition and molecular mobility caused by fiber annealing at elevated temperatures were studied with real-time NMR T2 relaxation experiments. The most pronounced annealing effects (changes in the phase composition) were observed for undrawn fibers with low molecular orientation. Annealing slows down for fibers produced at larger winding speed and especially those with a high draw ratio. Fiber processing conditions, i.e., winding speed and draw ratio, are found to affect the phase composition and molecular mobility in different phases. It was shown that the present NMR relaxation method provides a fast and accurate technique to analyze the phase composition of Nylon 6 fibers. The amount of rigid phase determined from NMR is in good agreement with the crystallinity of the fiber obtained using the traditional method for Nylon 6 fibers, which involves a combination of density measurement, wide-angle X-ray diffraction and C-13 NMR spectroscopy. Hence, the present NMR relaxation method greatly simplifies measurement of crystallinity in Nylon 6 fibers.