BOPET film, short for biaxially oriented polyethylene terephthalate film, is a film material made from polyester resin, which is produced by the reaction of terephthalic acid and ethylene glycol.
Properties of BOPET Film
Transparent with excellent optical performance, providing high optical clarity and refractive index.
Outstanding mechanical properties such as high strength, toughness, and impact resistance.
Excellent thermal stability, resistant to high-temperature sealing and low-temperature freezing.
Strong resistance to chemical corrosion, with good acid and alkali resistance.
Excellent barrier properties to prevent penetration and contamination of packaged goods by external substances like oxygen and moisture.
Applications of BOPET Film
BOPET film is widely used in the printing, electronics, film, and photovoltaic industries.
BOPET Film Production Process
The production of BOPET film mainly involves two steps: stretching and orientation. PET raw material is melted into a sheet film, which is then uniformly stretched and oriented in both lengthwise and crosswise directions through a series of stretching and cooling processes to form BOPET film with biaxial orientation properties.
I. BOPET Raw Material Pellets
For BOPET production, both single-layer and co-extruded composite films use two or more types of pellet materials. The proportion of these pellets varies depending on the type of film:
Resin with High Concentration of Additives: Mainly used to improve product performance, commonly known as anti-adhesion masterbatch pellets, used at about 10% to 30% (by mass).
Ultra-Bright Pellets without Additives: Commonly known as bright or white pellets, used at about 40% to 90% (by mass).
Recycled Pellets from Waste Film: Commonly known as recycled material, used at 0% to 45% (by mass). Recycled material is not added in the production of high-performance film varieties, such as capacitor film.
Special Functional Masterbatch Pellets: In addition to the above three types of raw material pellets, special functional masterbatch pellets are also used for special functional films, such as anti-static, wear-resistant, and UV-resistant masterbatches.
II. Anti-Adhesion Masterbatch Pellets
Like other plastic films, PET film also requires the use of anti-adhesion additives to solve the adhesion issues during film production and application. Untreated plastic films tend to "stick" under pressure during winding and after rolling, with thinner films experiencing more severe adhesion. Adhesion makes subsequent processing and use difficult, affecting unwinding speed and, in severe cases, making it impossible to use.
Different types of anti-adhesion agents are added to the polyester resin based on the film's application and performance requirements:
Inorganic
Organic
Thermosetting Organic Polymer
Organic-Inorganic Composite
Organic Silicon Resin
Common anti-adhesion agents are mainly inorganic and organic types.
For films with high optical performance requirements, the anti-adhesion agent should not affect the film's performance, especially its optical properties. Therefore, the refractive index of the anti-adhesion agent should be close to that of PET (1.64 at 25°C). The closer the refractive indices, the less impact on the film's optical properties. For films with lower optical performance requirements, anti-adhesion agents with similar refractive indices can be chosen according to performance requirements.
