Polyester film It exhibits good toughness, mechanical strength, and excellent transparency, but its surface smoothness is relatively poor. Adding a slip agent can result in slight haze. No additional additives are required. Polyester film is chemically inert to food. Heat sealing is challenging because it tends to shrink and become brittle due to crystallization. Consequently, adhesive sealing is commonly employed; however, BOPP heat-seal film manufacturers recommend laminating it with low-density polyethylene to take advantage of the latter’s superior heat-sealing properties.

　　Polyester film exhibits a very low water vapor transmission rate, comparable to that of low-density polyethylene, and also has low permeability to air and odors, similar to nylon. It is resistant to dilute acids and alkalis, but concentrated acids and alkalis can react with it. It is resistant to most solvents, oils, and fats.

　　Properties and Applications of Polyester Film

　　Polyester film exhibits excellent tear resistance, fold endurance, and abrasion resistance. It also boasts superior impact resistance, maintaining its integrity down to approximately –70°C. With outstanding electrical insulation properties, high dielectric strength, favorable dielectric performance, and a high volume resistivity, BOPP heat-seal film manufacturers note that unoriented polyester film can be thermoformed. After stretching but before heat setting, the film can serve as a shrink film, with a shrinkage temperature of around 100°C. It is amenable to vacuum metallization, yielding metallized films with excellent decorative appeal. These films find extensive applications in packaging, industry, and agriculture, including use as adhesive tape substrates, photosensitive film bases, and electrical insulating materials.

　　According to BOPP heat-seal film manufacturers, biaxially oriented polyester film boasts high mechanical strength, excellent optical properties, superior electrical insulation, compliance with environmental and health standards, readily available raw materials, environmentally friendly processing, and increasingly mature manufacturing technologies. Its applications are extremely broad; statistics indicate that there are nearly 2,000 different uses for polyester film. By tailoring its mechanical, optical, electrical, and thermal properties, it can meet the diverse requirements of various applications.

　　BOPP heat-seal film manufacturers believe that the following factors influence the film’s haze value.

　　1. The influence of additives. The particle size, distribution, type, and dosage of additives significantly affect haze values. Since these additives primarily act at the surface layer, a multi‑layer co‑extrusion process can be employed in equipment design to mitigate their impact on haze.

　　2. Influence of process conditions. Crystallization significantly affects haze values. During processing, crystal morphology and crystallinity continuously evolve, necessitating stringent control. Consequently, the production line must be equipped with machinery capable of precisely regulating crystallinity. The equipment should feature cast‑film units with adequate cooling capacity, a longitudinal stretching unit that can achieve high pre‑heat temperatures without sticking to the rollers, and individually driven rollers. Additionally, the horizontal stretching unit must provide sufficient thermal setting length, among other requirements.

　　3. The influence of raw materials. This primarily encompasses several aspects: first, the level of internal impurities, including residual catalyst; second, the base tone of the material; and third, the material’s stability.