How does the surface energy of polyethylene affect paint adhesion without primers?

The surface energy of polyethylene plays a critical role in paint adhesion, especially when primers are not used. Polyethylene has inherently low surface energy, typically ranging between 30-36 mN/m, which makes it difficult for paints to wet and adhere properly. This hydrophobic nature results in poor paint bonding, leading to issues like peeling, cracking, or uneven coverage.

To improve adhesion without primers, surface treatments such as flame treatment, plasma treatment, or corona discharge can be employed. These methods increase the surface energy by introducing polar functional groups, enhancing paint wettability. Mechanical abrasion or chemical etching can also help by creating a rougher surface for better mechanical interlocking.

Understanding these factors is essential for industries relying on painted polyethylene products, as proper surface preparation ensures durability and aesthetic quality. Without adequate treatment, paint adhesion remains unreliable, limiting polyethylene's applications in automotive, packaging, and consumer goods.