The comparative study of biodegradation of various blown films obtained from Poly (lactic) acid (PLA) has been studied via soil burial method. A total of 3-different types of films prepared from neat PLA and the reactive blends containing poly butylenes succinate-co-adipate (PBSA), and thermoplasticized starch (TPS); namely VPLA, PLA/PBSA, PLA/TPS respectively were the subjects of investigation. Several analytical techniques including weight loss method and analysis of mechanical properties were performed in each seven days interval until ninety days to elucidate the biodegradation in soil. The tensile modulus of VPLA and PLA/PBSA blown films were deteriorated to the tune of 60.32% and 71.28% respectively within 28 days, while PLA/TPS blown films recorded a significant reduction of 75.31% in the modulus value within 21 days of soil exposure compared to unexposed blown film samples. Similarly, blown films of PLA/TPS reported the highest rate of weight loss in the order of 40.06% in 90 days of soil burial with an estimated half-life of 103 days in soil environment compared to its counterparts. The depletion in both mechanical properties and weight of the film samples suggesting the occurrence of biodegradation in the real soil environment. Scanning electron microscopy (SEM) revealed the formation of coarse morphology for all three types of soil buried samples which trace of microbial action appeared on PLA/TPS films. Fourier transform infrared microscope (FTIR) showed the decrease in carbonyl index and variation in the intensities of carbonyl and hydroxyl peaks irrespective of the film samples after 90 days of soil exposure. Gel permeation chromatography (GPC) documented reduction in molecular weight and variation in polydispersity index (PDI) of post-exposed soil samples. The elemental analysis exhibited that the percentage of organic carbon and hydrogen content of all the films decreased while the oxygen percentage increased after soil burial due to the biodegradation of film specimens. Both Differential scanning calorimetry (DSC) and X-ray diffraction analysis (XRD) reported increase in crystallinity for soil exposed samples indicating the initiation of degradation kinetics preferably at the amorphous region of film composition. It has also been inferred that the biodegradation mechanism of VPLA and PLA/PBSA blown films predominantly driven by hydrolysis of ester bond. Contrastingly, the biodegradation kinetics in case of PLA/TPS film has been proceeded with microbial assimilation of TPS component which further thrived on hydrolysis of PLA component of the blown film system.

Graphic Abstract

中文翻译：

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土壤中掺入热塑性淀粉（TPS）和聚丁二酸丁二酸丁二酯（PBSA）生物聚合物对聚乳酸（PLA）吹膜的生物降解行为的比较

通过土壤掩埋法研究了从聚乳酸（PLA）获得的各种吹塑薄膜的生物降解的比较研究。由纯PLA和含有聚丁二酸丁二酯-己二酸酯共聚己二酸酯（PBSA）和热塑性淀粉（TPS）的反应性共混物制备的总共3种不同类型的薄膜; 分别是VPLA，PLA / PBSA，PLA / TPS是研究对象。每隔7天进行一次分析技术，包括失重法和机械性能分析，直到90天，以阐明土壤中的生物降解情况。VPLA和PLA / PBSA吹塑薄膜的拉伸模量在28天内分别下降了60.32％和71.28％，而PLA / TPS吹塑薄膜的拉伸模量则显着降低了75。与未暴露的吹膜样品相比，在暴露于土壤的21天内模量值达到31％。同样，PLA / TPS的吹塑薄膜在90天的土壤埋葬中报告了最高的失重率，约为40.06％，在土壤环境中的估计半衰期为103天。膜样品的机械性能和重量均耗竭，表明在实际土壤环境中发生了生物降解。扫描电子显微镜（SEM）揭示了所有三种土壤埋藏样品的粗大形态，在PLA / TPS膜上出现了微生物作用痕迹。傅立叶变换红外显微镜（FTIR）显示，土壤暴露90天后，无论膜样品如何，羰基指数均下降，羰基和羟基峰强度发生变化。凝胶渗透色谱法（GPC）记录了暴露后土壤样品的分子量降低和多分散指数（PDI）的变化。元素分析表明，由于膜样品的生物降解作用，土壤埋藏后所有膜的有机碳和氢含量百分比均降低，而氧含量则有所增加。差示扫描量热法（DSC）和X射线衍射分析（XRD）均报告了土壤暴露样品的结晶度增加，表明降解动力学的启动优选在膜组成的无定形区域开始。还已经推断出VPLA和PLA / PBSA吹塑薄膜的生物降解机理主要是由酯键的水解驱动的。相反，

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