Dicarboxylic Acids and Ketoacids Formed in Degradable Polyethylenes by Zip Depolymerization through a Cyclic Transition State
Dicarboxylic Acids and Ketoacids Formed in Degradable Polyethylenes by Zip Depolymerization through a Cyclic Transition State
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通过循环过渡态 Zip 解聚在可降解聚乙烯中形成二羧酸和酮酸
DOI：
10.1021/ma961489c
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发表时间：
1997
期刊：
影响因子：
5.5
通讯作者：
A. Albertsson
中科院分区：
文献类型：
--
作者：
S. Karlsson;M. Hakkarainen;A. Albertsson
研究了用淀粉和/或促氧化剂或光敏剂（Scott-Gilead配方[SG]）改性的6种不同的低密度聚乙烯（LDPE）薄膜形成的中间和最终降解产物。我们认为材料中不同程度形成的二羧酸和酮酸是由于二次氧化产物和通过循环过渡态的反向聚合机制而形成的。在光氧化初期形成烃类、酮类、羧酸和二羧酸，在降解最严重的材料中，酮类消失，几种酮酸出现，二羧酸的相对数量增加。在长时间的光氧化过程中，酮类和单羧酸被氧化为二羧酸，这解释了二羧酸含量高的原因。在热氧化的样品中，即使在最降解的样品中，酮和单羧酸的含量仍然很高。单羧酸和二羧酸在每100毫克聚合物中形成几微克，而酮和酮酸在每100毫克聚合物中形成的微克更少。以二甲基二硫代氨基甲酸铁（SG1）改性的LDPE最易发生光氧化，而含有淀粉和促氧化剂的LDPE （LDPE- mb）最易发生热氧化。降解后的LDPE-MB降解产物较少；例如，只有在80℃下热降解5周的紫外线激发样品中才能检测到降解产物。与淀粉填充材料相比，SG材料中形成了更多的酮和酮酸。
The intermediate and final degradation products formed in six different low-density polyethylene (LDPE) films modified with either starch and/or pro-oxidants or photosensitizers (Scott-Gilead formulation [SG]) were investigated. We propose that dicarboxylic acids and ketoacids, formed in the materials to varying degrees, are due to both secondary oxidation products and a zip depolymerization mechanism by backbiting through a cyclic transition state. Hydrocarbons, ketones, carboxylic acids and dicarboxylic acids are formed during early stages of photo-oxidation, and the ketones disappeared while several ketoacids appeared and the relative amount of dicarboxylic acids increased in the most severely degraded materials. During prolonged photo-oxidation, additional oxidation of ketones and monocarboxylic acids to dicarboxylic acids explains the high amount of dicarboxylic acids. In the thermooxidized samples the amount of ketones and monocarboxylic acids remained high even in the most degraded samples. Mono-and dicarboxylic acids were formed in several micrograms per 100 mg of polymer, while the ketones and ketoacids were formed in fewer micrograms per 100 mg of polymer. LDPE modified with the iron dimethyldithiocarbamate (SG1) was the most susceptible material to photooxidation, while LDPE containing starch and pro-oxidants (LDPE-MB) was the most susceptible material to thermo-oxidation. Degraded LDPE-MB demonstrated less formation of degradation products; e.g., only in UV-initiated samples thermally degraded at 80 degrees C for 5 weeks could degradation products be detected. Larger amounts of ketones and ketoacids were formed in the SG materials than in the starch-filled materials.