The effect of temperature and annealing on the phase composition, molecular mobility and the thickness of domains in high-density polyethylene
The effect of temperature and annealing on the phase composition, molecular mobility and the thickness of domains in high-density polyethylene
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DOI：
10.1016/j.polymer.2006.12.019
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发表时间：
2007-01-26
期刊：
影响因子：
4.6
通讯作者：
Litvinov, Victor M.
中科院分区：
文献类型：
--
作者：
Hedesiu, Cristian;Demco, Dan E.;Litvinov, Victor M.
分子的流动性，域的厚度和刚性，半刚性，和软馏分的高密度聚乙烯（HDPE）的量，其特征在于作为温度和退火时间的函数，使用时域和频域质子固态NMR。这些实验建立了在结晶相、半刚性晶体-非晶界面和非晶相的软分数中观察到分子迁移率的最大差异的温度范围，从而允许精确确定这些域的相组成和厚度。的域的厚度，这是由NMR确定的，是在良好的协议，通过小角X射线散射（SAXS）和透射电子显微镜（TEM）对同一样品的测量。在非晶相的分子流动性的变化时，增加温度和退火进行了讨论。它示出，退火伴随着结构重组的非晶层相邻的片层表面引起的连续移位的界面朝向内部的非晶区域，从而减少非晶层的厚度。最近介绍的方法用于测量畴的厚度的自旋扩散NMR实验与双量子偶极滤波器。的自旋扩散系数的温度依赖性报告的三个阶段的HDPE。首次比较了时域低场核磁共振和频域高场核磁共振自旋扩散实验的结果。(c)2006爱思唯尔有限公司保留所有权利。
Molecular mobility, the thickness of domains and the amount of rigid, semi-rigid, and soft fractions of high-density polyethylene (HDPE) were characterized as a function of temperature and annealing time using time- and frequency-domains proton solid-state NMR. These experiments established the temperature range for which the largest differences are observed in molecular mobility in crystalline phase, semi-rigid crystal-amorphous interface, and soft fraction of the amorphous phase allowing accurate determination of the phase composition and the thickness of these domains. The domain thickness, which was determined by NMR, is in good agreement to those measured by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) on the same sample. Changes in molecular mobility in the amorphous phase upon increasing temperature and annealing are discussed. It is shown that annealing is accompanied by structural reorganizations in the amorphous layer adjacent to the lamella surface causing a continuous shift of the interface towards the inner part of the amorphous regions and thus reducing the thickness of the amorphous layer. A recently introduced method was used for measuring the thickness of domains by a spin-diffusion NMR experiment with a double-quantum dipolar filter. The temperature dependence of the spin diffusivities is reported for the three phases of HDPE. For the first time results of spin-diffusion experiment performed by time-domain low-field NMR and frequency-domain high-field NMR are compared. (c) 2006 Elsevier Ltd. All rights reserved.