PET film is a thermoplastic film characterized by high transparency, excellent gloss, and superior gas barrier properties, making it widely used in packaging, optics, construction materials, pharmaceuticals, and other industries. Unprocessed, PET heat-seal film The surface tension can reach 40 dynes or higher. However, some inks are applied directly, resulting in suboptimal adhesion. Only by subjecting PET heat-seal films to a special treatment can improved adhesion be achieved.

　　Adhesion underpins most of a coating’s performance characteristics, including scratch resistance, water resistance, abrasion resistance, and chemical resistance. At present, there is no definitive scientific explanation for the fundamental mechanisms of adhesion. It is generally believed that substrates with high surface tension can achieve good adhesion. However, this theory does not readily apply to PET heat‑seal films. Among commonly used plastic film substrates, PET heat‑seal film ranks as the third most difficult to bond, following only PE and PP.

　　Corona treatment is a physical process that uses high‑voltage discharge to create microscopic surface cracks and introduce functional groups on the film surface. This method is effective for heat‑sealable films and is widely employed. Following corona treatment, the surface tension of PET heat‑sealable films increases significantly, enhancing wettability, while surface roughness also improves markedly. For typical adhesion requirements, corona treatment generally performs well. However, when customers demand exceptionally high adhesion, corona treatment alone cannot meet such stringent quality standards.

　　UV-curable coating solutions are curing coatings that harden when exposed to ultraviolet light. By applying a layer of UV‑curable coating onto PET heat‑seal films and then curing it with a UV lamp, a high‑hardness, transparent, scratch‑resistant coating is formed on the film. After UV curing, the hardness of the PET heat‑seal film is significantly enhanced, thereby broadening its range of applications.

　　During the use of heat-sealable films, PET heat-sealable films may reveal issues related to product storage.

　　1. Attention should be paid to the micropores of the heat-seal film, as its adhesion performance depends on whether moisture from the surface sealant and adhesive can penetrate the pressure-sensitive adhesive, thereby accelerating drying and integrating the product’s sealant into the heat-seal film itself. Therefore, the microporosity of the PET heat-seal film’s surface is a critical factor that must be carefully selected. If the PET heat-seal film has numerous defects in its micropores or exhibits high moisture absorption, its overall performance will be poor.

　　2. Pay attention to the adhesive on the surface of the heat-seal film. Adhesive is applied to the backing layer, and the film is typically wound into rolls only after it has completely dried. If the PET heat-seal film remains too moist, the layers will stick together tightly, making it difficult to separate during use—sometimes rendering the film unusable altogether. Therefore, proper storage precautions are essential.

　　3. When selecting PET heat-seal films, choose based on the specific characteristics of the application to ensure optimal performance.