The pro-oxidant additives used in the production of oxo-biodegradable polymers are generally organic salts of transition metals added during the processing of polyolefins. Transition metals accelerate the photooxidation and thermal oxidation of macromolecules, producing oxygenated fragments which are then used as nutrients by microorganisms in the biodegradation process. However, the use of these additives can lead to contamination of the environment by metals, which come free from the reactions. The aim of this study was to obtain an oxo-biodegradable polypropylene by processing flat films with distinct levels of benzoin, an organic substance free of transition metals, which is biodegradable. After extrusion ( = 0 h), samples were submitted to OIT analysis, which showed that benzoin favors the thermal oxidation process. Subsequently, the samples were subjected to accelerated ageing in a UV chamber and were characterized by dilute solution viscometry (DSV), FTIR, TGA, DSC and SEM. Results of the DSV analysis revealed a significant reduction in the viscosimetric average molar mass of the samples containing the additive, which was accompanied by a considerable increase in carbonyl groups, according to the carbonyl indexes calculated from the FTIR spectra. Thermogravimetric analysis of the aged samples containing benzoin indicated a greater loss of thermal stability and the DSC thermograms revealed a considerable reduction in the melting temperature of the oxo-biodegradable PP. The SEM images of the aged samples indicated that the presence of the additive favored the appearance of regions containing flaking and erosion. In general, the results clearly indicated that benzoin accelerated the photooxidation process during ageing by UV irradiation. Unlike organic salts of transition metals, benzoin seems to act in the initiation step of photo- and thermal oxidation, as demonstrated at the end of this study.

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从不含过渡金属的促氧化剂获得的可氧化生物降解聚丙烯的非生物降解表征

用于生产含氧生物降解聚合物的促氧化剂添加剂通常是在聚烯烃加工过程中添加的过渡金属有机盐。过渡金属加速大分子的光氧化和热氧化，产生含氧碎片，然后在生物降解过程中被微生物用作营养物质。然而，使用这些添加剂可能会导致环境被未参与反应的金属污染。本研究的目的是通过加工含有不同含量安息香（一种不含过渡金属且可生物降解的有机物质）的平板薄膜来获得可氧化生物降解的聚丙烯。挤出后（= 0 h），将样品进行 OIT 分析，结果表明安息香有利于热氧化过程。随后，样品在紫外室中进行加速老化，并通过稀溶液粘度计 (DSV)、FTIR、TGA、DSC 和 SEM 进行表征。根据 FTIR 光谱计算的羰基指数，DSV 分析结果显示，含有添加剂的样品的粘度平均摩尔质量显着降低，同时羰基显着增加。对含有安息香的老化样品的热重分析表明热稳定性损失较大，DSC 热分析图显示可氧化生物降解的 PP 的熔化温度显着降低。老化样品的 SEM 图像表明，添加剂的存在有利于出现剥落和腐蚀区域。总的来说，结果清楚地表明，安息香加速了紫外线照射老化过程中的光氧化过程。与过渡金属的有机盐不同，安息香似乎在光氧化和热氧化的引发步骤中起作用，如本研究末尾所证明的。