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Degradation of low-density polyethylene during extrusion. VI. Effects of oxygen content in air gap

机译:挤出过程中低密度聚乙烯的降解。 VI。气隙中氧气含量的影响

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In our previous papers polyethylene degradation during extrusion coating has been studied and the type of degradation products that are formed and from which step they originate have been discussed. A trained sensory panel has rated the off-flavor intensities in water samples that have been in contact with various extruded films. Encouraged by the results from these investigations and the documented synergism between aldehydes and ketones and aldehydes and carboxylic acids in off-flavor intensity, the present study was aimed at confirming the belief that the off-flavor depends on the presence of oxidative degradation products that have migrated from the film into the water. By decreasing the oxygen concentration in the atmosphere surrounding the extruded melt presence of the highly oxidized species (i.e., carbonyl compounds and carboxylic acids) would decrease and thus the off-flavor in the water should decline. From this study it could be concluded that the extrusion temperature and the oxygen content in the atmosphere nearest the molten film before quenching are the most important parameters for oxidative degradation and residence time in the air gap influence the amount of oxidative degradation products formed. Furthermore we concluded that the off-flavor intensity is strongly correlated to the surface oxidation index of the film. Carboxylic acids are present in the water extracts of extruded films and are related to the off-flavor intensities. (c) 2005 Wiley Periodicals, Inc.
机译:在我们以前的论文中,已经研究了在挤出涂布过程中聚乙烯的降解,并讨论了形成的降解产物的类型以及它们从哪一步产生。训练有素的感官小组评估了已经与各种挤出薄膜接触的水样品的异味强度。受这些研究结果以及醛,酮,醛和羧酸在异味强度方面的协同作用的鼓舞,本研究旨在证实以下观点:异味取决于氧化降解产物的存在。从胶片迁移到水中。通过降低在挤出的熔体周围的气氛中的氧浓度,高氧化性物质(即羰基化合物和羧酸)的存在将减少,因此水中的异味应减少。从该研究可以得出结论,在淬火之前,最接近熔融膜的气氛中的挤出温度和氧气含量是氧化降解的最重要参数,并且气隙中的停留时间会影响所形成的氧化降解产物的量。此外,我们得出的结论是,异味强度与薄膜的表面氧化指数密切相关。羧酸存在于挤出薄膜的水提取物中,并且与异味强度有关。 (c)2005年Wiley Periodicals,Inc.

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