Polyethylene is the most consumed plastic globally; however, its poor adhesiveness poses serious challenges, particularly in the fabrication of composites and the recycling of mixed plastic waste. While these unfavorable properties are conventionally improved by pretreating the polyethylene surface, the treated surface frequently reverts to its original state over time, which is an unresolved drawback. Here, we describe a novel adhesion system; a polyurethane adhesive penetrates an amorphous part of untreated polyethylene and they form a mixing layer at the adhesive interface. The interfacial mixing layer forms upon heat treatment, even below the melting point of polyethylene and the polymers bind tightly at the interface via entanglement. The peel strength increases with increasing the thickness of the mixing layer. While decreasing the molecular weight of polyurethane promotes inter-diffusion, it also causes a decline in the mechanical strength of the polyurethane adhesive layer. Polyurethanes with optimally balanced molecular weight exhibit superior adhesion due to balance diffusivity and mechanical strength.

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通过扩散对未处理的聚乙烯进行粘合：聚氨酯粘合剂分子量对聚乙烯渗透的影响

聚乙烯是全球消耗量最大的塑料；然而，其较差的粘合性带来了严峻的挑战，特别是在复合材料的制造和混合塑料废物的回收方面。虽然这些不利的性能通常通过预处理聚乙烯表面来改善，但经过处理的表面经常会随着时间的推移恢复到其原始状态，这是一个尚未解决的缺点。在这里，我们描述了一种新颖的粘合系统；聚氨酯粘合剂渗透未经处理的聚乙烯的无定形部分，并在粘合剂界面形成混合层。界面混合层在热处理时形成，甚至低于聚乙烯的熔点，并且聚合物通过缠结在界面处紧密结合。剥离强度随着混合层厚度的增加而增加。降低聚氨酯的分子量在促进相互扩散的同时，也会导致聚氨酯胶层的机械强度下降。具有最佳平衡分子量的聚氨酯由于平衡的扩散性和机械强度而表现出优异的粘合力。