Advantages of PET material
1. It has good mechanical properties, the impact strength is 3~5 times that of other films, and it has good folding resistance.
2. Resistant to oil, fat, dilute acid, dilute alkali, and most solvents.
3. The heat resistance of pure PET is not high, and the heat distortion temperature is only about 85°C, but it is greatly improved after strengthening treatment. The mechanical properties of PET reinforced with glass fiber are similar to engineering plastics such as PC and
PA, and the thermal deformation temperature can reach 225°C; PET has good heat aging resistance, and the embrittlement temperature is -70°C, and it still has a certain Toughness; PET is not easy to burn, the flame is yellow, and the burning oil drips.
4. The gas and water vapor permeability is low, and it has excellent gas, water, oil and odor performance.
5. High transparency, can
Block ultraviolet rays, good gloss.
6. Non-toxic, tasteless, hygienic and safe, can be directly used in food packaging.
About properties
PET is a milky white or light yellow highly crystalline polymer with a smooth and shiny surface. Creep resistance, fatigue resistance, abrasion resistance and dimensional stability are good, low wear and high hardness, with the greatest toughness among thermoplastics: good electrical insulation performance, less affected by temperature, but poor corona resistance. Non-toxic, weather resistance, good stability against chemicals, low water absorption, resistant to weak acids and organic solvents, but not resistant to hot water soaking, not alkali resistant.
PET resin has a high glass transition temperature, slow crystallization speed, long molding cycle, long molding cycle, large molding shrinkage, poor dimensional stability, brittle crystallized molding, and low heat resistance.
Through the improvement of nucleating agent, crystallization agent and glass fiber reinforcement, PET has the following characteristics in addition to the properties of PBT.
1. The heat distortion temperature and long-term use temperature are the highest among thermoplastic
General Engineering Plastics 2. Because of the high heat resistance, reinforced PET is immersed in a solder bath at 250°C for 10 seconds, and it hardly deforms or changes color. It is especially suitable for preparing electronic and electrical parts for soldering:
3. The bending strength is 200MPa, the modulus of elasticity reaches 4000MPa, the creep resistance and fatigue resistance are also very good, the surface hardness is high, and the mechanical properties are similar to thermosetting plastics.
4. Since the price of ethylene glycol used in the production of PET is almost half that of butanediol used in the production of PBT, PET resin and reinforced PET are the lowest prices among engineering plastics, and have high cost performance.
About the application
PET is mainly used for fibers, and a small amount is used for films and engineering plastics. PET fibers are mainly used in the textile industry. PET film is mainly used for electrical insulation materials, such as capacitors, cable insulation, printed circuit wiring substrates, electrode slot insulation, etc. Another application field of PET film is film base and base tape, such as movie film, X-ray film, audio tape, electronic computer tape, etc. PET films are also made of metallized films, such as gold and silver wires, micro capacitor films, etc., using vacuum aluminum. Another use of PET is blow molding products, polyester stretch bottles for packaging.
Glass fiber reinforced PET is suitable for electrical and electronic and automotive industries, used for various coil bobbins, transformers, TV sets, tape recorder parts and casings, automotive lamp holders, lampshades, incandescent lamp holders, relays, sun rectifiers, etc.
About processing
The molding process of PET can be injection molding, extrusion, blow molding, coating, bonding, machining, electroplating, vacuum metallization, and printing. The following mainly introduces two kinds.
1. Injection molding level ①Temperature setting: nozzle: 280~295°C, front section 270~275°C, middle forging 265~275°C, rear section 250-270°C; screw speed 50~100rpm, mold temperature 30~85°C , The non-crystalline mold should be below 70℃, and the back pressure should be 5-15KG. ②Try a dehumidifying dryer, the material tube temperature is 240~280°C, the injection pressure is 500~1400Pa, the injection molding temperature is 260~280°C, the drying temperature is 120~140°C, and the required time is 2~5 hours.
2. For the film grade, pre-dry the PET resin slices to prevent hydrolysis, then extrude the amorphous thick slices through a T-shaped die in the extruder at 280 ° C, and quench them with a cooling drum or cooling liquid to keep them Amorphous to allow for stretch orientation. The thick sheet is biaxially stretched by a tenter to become a PET film. Longitudinal stretching is to preheat the thick sheet to 86~87°C, and stretch it about 3 times along the plane extension direction of the thick sheet at this temperature, so that the orientation can increase the crystallinity and reach a higher temperature: transverse stretching preheating temperature 98~100℃, stretching temperature 100~120℃, drawing ratio 2.5~4.0, heat setting temperature 230~240℃. The film after vertical and horizontal stretching needs to be heat-set to eliminate the film deformation caused by stretching and make a film with better thermal stability
