Classification and characteristics of polyester film [PET]

  Polyester film is a high-grade film made of high-quality fiber-grade polyester chips (viscosity 0.64) as the main raw material, using advanced technology formula, through drying, melting, extrusion, casting and stretching.

  (1) Classification according to the materials and production processes of the polyester film

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 (abbreviated as BOPET) is a glossy material (also known as a large glossy material, that is, titanium dioxide is added to the raw material polyester chips, after drying, melting, extrusion, casting and vertical and horizontal The stretched high-grade film, 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 3 times that of PC film and nylon film. times, the impact strength is 3-5 times that of BOPP film, with excellent abrasion resistance, folding resistance, pinhole resistance and tear resistance, etc.; heat shrinkage is very small, at 120 ° C, 15 minutes After shrinking only 1.25%; has good antistatic properties, easy to use vacuum aluminum plating, can be coated with PVDC, so as to improve 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. Therefore, it is widely used.

  2. Uniaxially stretched polyester film (CPET for short) is a film that is dried, melted, extruded, cast and longitudinally stretched using semi-matte material (no titanium dioxide is added to the raw material polyester chips). The polyester film has the lowest level and price, and is mainly used for pharmaceutical tablet packaging. Due to the small amount of use, manufacturers are less likely to consume them on a large scale, accounting for about 5% of the polyester film category. Chinese enterprises also import less, and the standard thickness is 150μm. Uses of polyester film [PET]

  Because the characteristics of polyester film determine its different uses. Polyester films with 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 insulation performance and high breakdown voltage, it is specially used for electronic and electrical insulation materials. 80μm, 100μm and 125μm (microns). These include wire and cable insulation films (25-75μm thick) and touch switch insulation films (50-75μm).

  2. Capacitor 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. Card protection film. It has good transparency, high stiffness, good thermal stability, smooth appearance, excellent winding performance, average longitudinal and transverse tensile properties, and excellent performance such as waterproof, oil-proof and chemical-proof. It is specially used for the maintenance packaging of pictures, documents, documents and office supplies, so that it is flat and beautiful after being hot stamped as a maintenance film, and can maintain the clarity and non-deformation of the original. 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 membrane. 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. The details are as follows:

①Semi-reinforced film. The most important 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 separation force with certain resins. It is mainly suitable for small dimensional changes during high temperature processing or as a transfer carrier. Conventional specification thickness is 9μm, 12μm, 15μm, 19μm, 25μm, 36μm.

③Printing composite packaging film. The main features are good transparency, good penetration resistance, excellent chemical resistance, temperature resistance and moisture resistance. It is suitable for the packaging of frozen food and food, pharmaceuticals, industrial products and cosmetics. Commonly used standard thicknesses are 12 μm, 15 μm, 23 μm, and 36 μm.

④Aluminized film. The main features are high strength, good temperature and chemical resistance, good processing and anti-aging properties, and proper corona treatment, which makes the adhesion of the aluminum layer and the film stronger. After being used for aluminum plating, it can be widely used in the packaging of tea, milk powder, candy, biscuits, etc. It can also be used as a decorative film such as string flower handicrafts and Christmas trees; it is also suitable for printing compounding or cardboard compounding. Conventional standard thicknesses are 12 μm, 16 μm, 25 μm, and 36 μm.

⑤ Magnetic recording film. It has the characteristics of good dimensional stability, average thickness and high tensile strength. Base film and special packaging film for magnetic recording data. Including audio and video tape base (common standard thickness is 9-12μm) and black film (common standard thickness is 35-36μm).

The safety film is generally BOPET. Of course, the ordinary safety film also needs to have color plating or other secondary processing processes, and the thickness is generally more than 100μm. The safety film is integrated with the glass by using its special adhesive, so as to achieve the purpose of maintenance. This is why there are many domestic film manufacturers, but one of the reasons why there are no safety film manufacturers.

There is also the fact that PET can withstand relatively high temperatures, but the bottles used for beverage packaging (Coke, pure water, etc.) are made by blow molding process, and there is no heat setting process, so they can only withstand a temperature of about 70 degrees.