聚乙烯地膜降解过程与机理研究进展

为探讨聚乙烯地膜的降解过程及影响因素,从聚乙烯材料的分子结构与特性入手,结合国内外最新研究进展,系统论述了聚乙烯分子的降解过程、产物、机理与作用因素。文章指出聚乙烯分子较高的结晶度与相对分子质量、较强的疏水性与分子间作用力是导致其难以降解的主要因素;其中,聚乙烯分子间共价键的氧化断裂是整个降解过程的限速反应。环境中较强的光能、热能、机械作用力等能够促进聚乙烯分子键的氧化断裂,使聚乙烯分子非结晶区及小型结晶区域解聚成亲水性低聚物或小分子,并最终在微生物作用下完全分解为CO_2、H_2O、CH_4、生物质等微生物代谢产物。深入系统开展聚乙烯分子降解机理的系统研究,不仅可以科学评价残留地膜对环境的影响,而且能够指导聚乙烯地膜配方改进,降低聚乙烯地膜残留污染。

A review on polyethylene mulch film degradation

To provide insight on the degradation process of polyethylene mulch films, the progress of the most recent studies were widely reviewed, and a systematic analysis was conducted on the degradation pathway, product, mechanism, and influencing factors of polyethylene mulch films based on its molecular structure and physicochemical properties. It was noted that the high crystallinity, molecular weight, hydrophobicity, and strong intermolecular bond made polyethylene hard to degrade naturally; molecular oxidation was the initial and rate-limiting step in the chain scission and degradation pathway. Many studies showed that high ultraviolet radiation, heat, and mechanical forces could accelerate the oxidative degradation of polyethylene molecular bond, causing depolymerization of non-crystalline and small crystalline parts to hydrophilic monomers or oligomers, which would break down further to CO₂, H₂O, CH₄, biomass, or other microbiotic metabolites through microorganism bioassimilation. Thorough examination of the pathways and mechanisms that are involved in polyethylene degradation could provide support for the scientific evaluation of the potential environmental hazards that are caused by mulch film residuals and potentially limit mulch film residue pollution by modifying the formulation of mulch film.