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首页> 外文期刊>Journal of Polymers and the Environment >The Effect of Ultraviolet Radiation on the Hyperelastic Behavior of Polyurea
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The Effect of Ultraviolet Radiation on the Hyperelastic Behavior of Polyurea

机译：紫外线辐射对聚脲超弹性行为的影响

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Polyurea is widely used in military and civilian applications, where long durations of exposure to the sun is common. Extended ultraviolet exposure can deteriorate the mechanical performance of the material to suboptimal levels. This study reports on the hyperelastic behavior of polyurea as a function of exposure duration to ultraviolet radiation. Initially, five sets of samples were continuously exposed to ultraviolet radiation for different durations up to 15 weeks. An additional set of samples were kept unexposed to report on the properties of an as-cast polyurea control. The samples were then loaded uniaxially in tension under a quasi-static loading rate () using a standard load frame. All exposed samples exhibited incremental color changes, which ranged from transparent yellow in virgin samples to opaque tan after 15 weeks of exposure. Changes in color were observed as early as 3 weeks of ultraviolet exposure. In addition to discoloration, crazing developed in all samples for exposure durations of 3 weeks and beyond. The size of the cracks increased as the duration of exposure continued. Postmortem examination indicated the initial microcracks grew due to loading and were visible to the naked eye. Discoloration and crazing were attributed to the formation of a thin ultraviolet-degraded layer due to the interaction of oxygen and ultraviolet light with the chromophoric groups in the polyurea macromolecule. The hyperelastic behavior was studied by fitting the stress-strain data into a four-term Ogden model. The overall hyperelastic behavior of polyurea remained unchanged even after 15 weeks of continuous ultraviolet exposure, where no permanent failure (except the ultraviolet-induced cracks) was recorded at the gauge length up to 250% strain. The values of the fitting parameters were nearly identical, supporting the conclusion of the insensitivity of polyurea hyperelastic behavior to ultraviolet radiation.
机译：聚脲广泛用于军事和民用领域，在这些领域中，长时间暴露在阳光下很常见。长时间暴露在紫外线下会使材料的机械性能下降到次优水平。这项研究报告了聚脲的超弹性行为与紫外线暴露时间的关系。最初，将五组样品连续暴露于紫外线辐射，持续时间长达15周。保持另一组样品未暴露以报告铸态聚脲对照的性质。然后使用标准加载框架以准静态加载速率（）将样品单轴加载。所有暴露的样品均显示出递增的颜色变化，从原始样品中的透明黄色到暴露15周后的不透明棕褐色。最早在紫外线照射3周后观察到颜色变化。除变色外，所有样品在暴露时间为3周及以上的地方均出现龟裂。裂纹的大小随着暴露时间的延长而增加。验尸表明最初的微裂纹是由于载荷而增长的，肉眼可见。由于氧气和紫外线与聚脲大分子中的发色基团的相互作用，导致变色和开裂归因于薄薄的紫外线降解层的形成。通过将应力应变数据拟合为四项Ogden模型来研究超弹性行为。即使连续暴露15周后，聚脲的总体超弹性行为也保持不变，在250 mm应变长的情况下，没有记录到永久性破坏（紫外线引起的裂纹除外）。拟合参数的值几乎相同，支持了聚脲超弹性行为对紫外线不敏感的结论。

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