High-quality polyester film (PET) for a wide range of applications

Polyester film is made of polyethylene terephthalate as raw material, made into thick sheet by extrusion method, and then made of biaxially stretched film material. At the same time, it is a kind of polymer plastic film, which is more and more favored by consumers because of its excellent comprehensive performance. As my country’s current production and technical level still can not meet the needs of the market, some still need to rely on imports. It is a colorless, transparent and glossy film with excellent mechanical properties, high rigidity, hardness and toughness, puncture resistance, friction resistance, high temperature and low temperature resistance, chemical resistance, oil resistance, air tightness and fragrance retention. Good, it is one of the commonly used barrier composite film substrates. However, the price of polyester film is relatively high, and the general thickness is 12micro;m. It is often used as the outer layer material of retort packaging, and has good printability. Furthermore, due to the complexity and difficulty of judgment of polyester film, it brings a lot of difficulties to customs supervision. To this end, we have learned from relevant professional companies about the commodity knowledge of polyester film and the relevant problems in the current import process.

First, according to the production of polyester film materials and production process classification
According to the different raw materials and stretching processes used in the production of polyester film, it can be divided into the following two types:
1. Biaxially oriented polyester film (BOPET for short) is made of glossy material (also called big glossy material, that is, titanium dioxide is added to the raw material polyester chips, after drying, melting, extrusion, casting and vertical and horizontal A stretched high-grade film with a wide range of uses. BOPET film has the characteristics of high strength, good rigidity, transparency and high gloss; odorless, tasteless, colorless, non-toxic, outstanding toughness; its tensile strength is PC film, nylon 3 times that of the film, the impact strength is 3-5 times that of the BOPP film, and has excellent abrasion resistance, folding resistance, pinhole resistance and tear resistance, etc.; heat shrinkage is very small, at 120°C under , shrinks only 1.25% after 15 minutes; has good antistatic properties, easy to vacuum aluminum, can be coated with PVDC, thereby improving its heat sealability, barrier properties and printing adhesion; BOPET also has good heat resistance , Excellent cooking resistance, low temperature freezing resistance, good oil resistance and chemical resistance, etc. BOPET film cannot be dissolved by most chemicals except nitrobenzene, chloroform and benzyl alcohol.
However, BOPET will be attacked by strong alkali, so care should be taken when using it. BOPET film has low water absorption and good water resistance, and is suitable for packaging foods with high water content.

2.Uniaxially stretched polyester film (CPET for short) is a film that is dried, melted, extruded, cast and longitudinally stretched by using semi-matte material (no titanium dioxide is added to the raw polyester chips). Ester film has the lowest grade and price, and is mainly used for pharmaceutical tablet packaging. Due to the small amount of use, the manufacturers are less mass-produced, accounting for about 5% of the polyester film field, and Chinese enterprises also import less, and the standard thickness is 150μm.

Second, according to the use of polyester film classification
Due to the characteristics of polyester film, its different uses are determined. Polyester films for different uses have different requirements for raw materials, additives and processing techniques, and their thickness and technical indicators are also different; in addition, only BOPET has multiple uses, so the films classified according to use are BOPET. It can be divided into the following categories:

1.Electrical insulating film. Due to its good electrical, mechanical, thermal and chemical inertness, good insulating properties and high breakdown voltage, it is specially used for electronic and electrical insulating materials. 80μm, 100μm and 125μm (microns). These include wire and cable insulation films (25-75μm thick) and touch switch insulation films (50-75μm).

2.Capacitive film. It has the characteristics of high tensile strength, high dielectric constant, low loss factor, good thickness uniformity, good electrical properties, and high resistance, and has been widely used in capacitor dielectrics and insulating spacers. Commonly used standard thicknesses are 3.5μm, 3.8μm, 4μm, 4.3μm, 4.8μm, 5μm, 6μm, 8μm, 9μm, 9.8μm, 10μm, 12μm.

3.Protective film. It has good transparency, high stiffness, good thermal stability, excellent rolling performance with smooth surface, uniform longitudinal and lateral tensile properties, and excellent performance such as waterproof, oil-proof and chemical-proof. It is specially used for the protective packaging of pictures, documents, documents and office supplies, so that it is flat and beautiful after hot stamping as a protective film, and can keep the originals clear and non-deformed. Commonly used standard thicknesses are 10.75μm, 12μm, 15μm, 25μm, 28μm, 30μm, 36μm, 45μm, 55μm, 65μm, 70μm, of which more than 15μm are mainly used as laser anti-counterfeiting base film or high-grade protective card film.

4. Universal film. With excellent strength and dimensional stability, cold resistance and chemical stability, it is widely used in composite packaging, photosensitive film, metal evaporation, audio and video and other substrates. Specifically, there are the following:
① Semi-strengthened film. The main feature is that the longitudinal tensile strength is large, and it is not easy to break under large tensile force. It is mainly used for packaging seals of boxed items. Commonly used standard thicknesses are 20 μm, 28 μm, 30 μm, 36 μm, and 50 μm.
②Bronzing film. The biggest features are good tensile strength and transparency, stable thermal properties, and low bonding force with certain resins. It is mainly suitable for small dimensional changes during high temperature processing or as a transfer carrier. Conventional standard thicknesses are 9 μm, 12 μm, 15 μm, 19 μm, 25 μm, 36 μm.