Abstract: Polyethylene bags, crafted from polyethylene film, are prevalent in the packaging industry, valued for their lightweight, transparent, soft, and durable properties. They find extensive use in varied sectors, including garment and food packaging. However, these bags contain migratable components such as openers, plasticizers, and other unstable polymers. These components can migrate, causing adverse effects, such as surface stains on nylon fabrics, impacting the quality and visual appeal of the fabrics. Therefore, investigating the adsorption mechanism between the migratable components in LDPE film and the surface of PU nylon fabrics is crucial to mitigate the impact of retained stains on PU nylon fabrics.
To elucidate the mechanism behind the visually visible oily stains on the surface of polyurethane (PU)-coated nylon garments wrapped in low-density polyethylene (LDPE) film, this study employed a combination of experimental testing and molecular dynamics simulation. Initially, the composition of the oily stains on the surface of the PU-coated nylon fabrics and the migratory components of the LDPE film were identified. Subsequently, a comparative analysis of the compositions was conducted. This comparison identified two chemicals: oleic acid amide and erucic acid amide, which are fatty amide slip agents in LDPE. Therefore, this research, via a blend of experimental testing and molecular dynamics simulation, determined that the main contributors to the oily stains appearing on the surface of PU nylon fabrics are the fatty amide slip agents present in LDPE films. Further microstructural analysis illustrated that the migratable components interact closely with the surface of the nylon fabric, forming a cauliflower-like structure. The PU-coated surface of the nylon fabric demonstrated notable oleophilic and hydrophobic properties. Molecular dynamics simulation results revealed that the migratory components in the polyethylene film and the nylon fabric surface primarily adhered through H-bonds and van der Waals forces, with -OH, -NH2, and -CO in the PU producing the principal bonding sites with the polar groups (NCO) of fatty amides.
Through this multifaceted approach, the research clarified the microscopic adsorption mechanism between the fatty amide slip agents—oleamide and erucic acid amide—and PU, in LDPE films. These insights can guide the development of strategies to understand and prevent the occurrence of oily stains during the garment packaging process, offering technical support for the selection of suitable slip agents in garment packaging materials.

Key words: polyethylene film, migratory component, nylon fabric, polyurethane coating, adsorption, molecular dynamic simulation

摘要： 为了阐明低密度聚乙烯（LDPE）膜包装聚氨酯（PU）涂层锦纶衣物时，在衣物表面产生视觉可见油性污渍的吸附机理。采用试验测试与分子动力学模拟相结合的方法，鉴定出油性污渍的主要化学成分为油酸酰胺和芥酸酰胺，这与LDPE膜中脂肪酰胺类开口剂组分一致。从分子尺度模拟LDPE中脂肪酰胺开口剂与锦纶织物PU层之间的吸附过程，以阐明两者之间的吸附的机理。微观结构分析表明：可迁移组分与锦纶织物表面形成了紧密的菜花状结构，PU锦纶织物表面表现出明显的亲油疏水特性。分子动力学模拟结果表明：LDPE膜中的可迁移组分与PU锦纶织物表面主要是以H键和范德华力的作用形成强烈的物理吸附，其中PU中的—OH、—NH2和—CO与脂肪酰胺类的极性基团（NCO）产生主要的结合位点。该研究揭示了LDPE膜中脂肪酰胺类开口剂与涂层PU锦纶织物的吸附机理，为服装包装材料上常用的开口剂的筛选提供了理论支持。

关键词: 聚乙烯膜, 可迁移组分, 锦纶织物, 聚氨酯涂层, 吸附, 分子动力模拟