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首页> 外文期刊>Journal of Applied Polymer Science >MECHANICAL RELAXATIONS AND DIFFUSIVE CHANGES IN LINEAR LOW DENSITY POLYETHYLENE (LLDPE) FILMS SUBJECT TO INDUCED STRETCHING
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MECHANICAL RELAXATIONS AND DIFFUSIVE CHANGES IN LINEAR LOW DENSITY POLYETHYLENE (LLDPE) FILMS SUBJECT TO INDUCED STRETCHING

机译：线性低密度聚乙烯（LLDPE）薄膜受诱导拉伸的力学松弛和扩散变化

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An analysis of the diffusion of oxygen and carbon dioxide through linear low density polyethylene (LLDPE) subjected to longitudinal and transversal induced stretching in the ratio 2:1, is presented in this paper. The relaxation behavior of two coextruded LLDPE films prepared from copolymers of ethylene-1-octene is reported as well. The spectra, expressed in terms of loss tan delta, present a gamma relaxation shifted 5 degrees C to 10 degrees C in the LLDPE1 with respect to the LLDPE2 when the stretching was longitudinal. This relaxation is lower in intensity than the one exhibited for conventional low-density polyethylene of the same crystallinity. Increasing the temperature order, a beta relaxation process appears as an ostensible shoulder of the first of two relaxation processes, called alpha' and alpha '', detected in the alpha region. The beta relaxation, which is believed to be produced by motion taking place in the amorphous and interfacial regions, appears as two overlapping peaks centered at -36 degrees C and -30 degrees C for a longitudinal stretching and at -34 degrees C and -28 degrees C for a transversal stretching at 1 Hz. In relation to this fact, we observed a slight increase in the T-alpha of the LLDPE2 with respect to the LLDPE1, which is greater in the transversally stretched polymers than in the longitudinal ones. The values of the activation energy corresponding to the second peak of the beta relaxation were obtained for the films subjected to stretching in longitudinal and transversal directions to the processing orientation. The study of the diffusional characteristics of oxygen and carbon dioxide through the films shows the temperature is related to the region for which the alpha processes are given. An anomalous behavior of the diffusion coefficient with the temperature is observed suggesting general movements around the amorphous segments and crystalline entities. The increase with the temperature of both parameters (diffusion and permeability) can be attributed to a change in the gas solubility. This increase is greater for CO2 than for O-2, which we interpret as a plastificant effect of the CO2. Finally, the activation energies from diffusion coefficient and permeability are analyzed in terms of Arrhenius. The results show that the temperature dependence of the diffusive parameters may not be a simply activated process as a consequence of the fact that the diffusional characteristics of the films depend on their morphology which, in turn, is changing with temperature. Little changes are observed when the films are subjected to any kind of stretching. In this sense, we think that the orientation by tensile drawing will decrease the conformational entropy involved in melting processes and, as a consequence, will reduce both the permeability and the apparent diffusion coefficients. (C) 1996 John Wiley & Sons, Inc. [References: 41]
机译：本文介绍了线性和低密度聚乙烯（LLDPE）通过纵向和横向以2：1的比例拉伸时氧气和二氧化碳的扩散分析。还报道了由乙烯-1-辛烯的共聚物制备的两种共挤出的LLDPE薄膜的弛豫行为。当纵向拉伸时，相对于LLDPE2，以损耗tanδ表示的光谱呈现出在LLDPE1中相对于LLDPE2的γ弛豫位移了5℃至10℃。这种弛豫强度低于相同结晶度的常规低密度聚乙烯所表现出的弛豫强度。随着温度顺序的增加，β弛豫过程看起来像是在alpha区域中检测到的两个弛豫过程中的第一个，即alpha'和alpha''的表面上的肩膀。 β松弛被认为是通过在无定形和界面区域中发生的运动而产生的，表现为两个重叠的峰，分别在-36℃和-30℃处纵向拉伸，在-34℃和-28处1赫兹横向拉伸的最大摄氏温度C。关于这一事实，我们观察到相对于LLDPE1，LLDPE2的T-alpha略有增加，在横向拉伸的聚合物中比在纵向的聚合物中更大。对于沿纵向和横向拉伸至加工取向的膜，获得了与β弛豫的第二个峰相对应的活化能的值。对氧气和二氧化碳在薄膜中的扩散特性的研究表明，温度与给出阿尔法过程的区域有关。观察到扩散系数随温度的异常行为，表明在非晶链段和晶体实体周围的一般运动。两个参数（扩散和渗透率）随温度的升高可归因于气体溶解度的变化。对于CO2，这种增加要比对O-2的增加大，我们将其解释为CO2的增效作用。最后，根据阿雷尼乌斯分析了扩散系数和渗透率产生的活化能。结果表明，由于薄膜的扩散特性取决于其形貌，而形貌随温度而变化，因此，扩散参数的温度依赖性可能不是简单激活的过程。当薄膜进行任何类型的拉伸时，观察到的变化很小。从这个意义上讲，我们认为通过拉伸拉伸的取向将降低熔融过程中涉及的构象熵，并因此降低渗透率和表观扩散系数。 （C）1996 John Wiley＆Sons，Inc. [参考：41]

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