High-Frequency Ultrasonic Studies of Poly(ethylene), Poly(propylene), and Poly(vinyl chloride)
High-Frequency Ultrasonic Studies of Poly(ethylene), Poly(propylene), and Poly(vinyl chloride)
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聚乙烯、聚丙烯和聚氯乙烯的高频超声研究
DOI：
10.1021/ma60059a021
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发表时间：
1977
期刊：
影响因子：
5.5
通讯作者：
D. W. Phillips
中科院分区：
文献类型：
--
作者：
A. North;R. Pethrick;D. W. Phillips
报告了在 0.1 至 1.0 GHz 的频率范围和 230 至 303 K 的温度范围内对聚乙烯、聚丙烯和聚氯乙烯薄膜进行的超声波衰减测量。这些数据与已发表的低频超声波衰减和高频布里尔朗散射测量的观察结果很好地相关。在聚丙烯结晶样品的情况下，高频吸收的降低归因于晶粒间热弹性损失的松弛。聚乙烯中衰减的增加归因于不同模量域（微晶）的散射。对于聚氯乙烯，可以观察塑化对背景热激活结构弛豫过程的影响。无定形聚合物材料在低频（约 1 Hz）下机械能的耗散可以用归因于特定分子弛豫过程的粘弹性弛豫来充分描述。 1 在正常声波和超声波频率范围内也是如此。然而，在高频（100 MHz 以上）时，额外的耗散过程变得很重要。 2'5 其中两个是声子-声子散射，其中传播的波与热声子相互作用，以及弹性波在模量不连续处的散射，当域尺寸（或域间分离）与超声波波长的超音速相当时，弹性波发生在不同形态域之间的边界处。首次研究 GHz 区域的声衰减时选择了三种聚合物：聚乙烯、聚丙烯和聚氯乙烯，它们表现出一系列的形态以及不同的链间相互作用势。本研究的目的是确定高频超声观测是否可用于观察通常使用传统方法无法检测到的形态相关现象，并提供有关此类固体中声子过程的信息。
Ultrasonic attenuation measurements on films of poly (ethylene), poly (propylene), and poly (vinyl chlo-ride) are reported over a frequency range of 0.1 to 1.0 GHz and over a temperature range from 230 to 303 K. The data correlate wellwith published observations from lower frequency ultrasonic attenuation and higher frequency Bril-louin scattering measurements. In the case of a crystalline sample of poly (propylene) a decrease in the high-frequen-cy absorption is attributed to relaxationof an intergranular thermoelastic loss. An increase in the attenuation in poly (ethylene) is ascribed to scattering by domains of different modulus (crystallites). In the case of poly (vinyl chlo-ride) it is possible to observe the effectof plasticization on the background thermally activated structural relaxation process.The dissipation of mechanical energy in amorphous polymeric materials at low frequencies (ca. 1 Hz) can be described adequately in terms of viscoelastic relaxation ascribable to specific molecular relaxation processes. 1 The same is true through the normal acoustic and ultrasonic frequency ranges. However, at high frequencies (above 100 MHz) additional dissipation processes become important. 2'5 Two such are phonon-phonon scattering, in which the propagating wave interacts with thermal phonons, and the scattering of elastic waves at the discontinuity of modulus, which occurs at the boundary between different morphological domains when the domain size (or interdomain separation) becomes comparable with the hyper-sound of ultra-sound wavelength. The three polymers chosen for this first study of acoustic attenuation in the GHz region, poly (ethylene), polypropyl-ene), and poly (vinyl chloride), exhibit a range of morphologies as well as different interchain interaction potentials. The aim of this study was to determine whether high-frequency ultrasonic observations could be used to observe morphology-related phenomena not usually detected using conventional methods and to give information on phonon processes in such solids.