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PET plastic is the abbreviation of polystylene terephthalate, which is called pet or PETP for short. Polyethylene terephthalate plastics mainly include polyethylene terephthalate pet and polybutylene terephthalate PBT. Polyethylene terephthalate is also commonly known as polyester resin. It is a condensation polymer of terephthalic acid and ethylene glycol. Together with PBT, it is collectively referred to as thermoplastic polyester, or saturated polyester.
The molecular structure of PET plastic is symmetrical at the highest point, and it has a certain ability of crystallization orientation, so it has relatively high film-forming property and formability. PET plastic has very good optical properties and weather resistance, and amorphous PET plastic has good optical transparency.
In addition, pet plastic has excellent wear resistance, friction, dimensional stability and electrical insulation. PET bottles are widely used because of their high strength, good transparency, non-toxic, impermeable, light weight and high production efficiency. The molecular chain structure of PBT and pet is similar, and most of the properties are the same, but the main chain of the molecule is changed from two methylene to four, so the molecule is more flexible and the processing performance is better.
Pet is a milky white or light yellow crystalline polymer with the highest point, and its surface is smooth and shiny. It has good creep resistance, fatigue resistance, friction resistance, low wear and high hardness, and has the greatest toughness among thermoplastics; The electrical insulation performance is good, and it is less affected by temperature, but the corona resistance is relatively poor. Non toxic, weather resistant, chemical resistant, good stability, high moisture absorption, drying after molding is necessary. Resistant to weak acids and organic solvents, but not resistant to hot water immersion and alkali.
PET resin has high glass transition temperature, slow crystallization speed, long molding cycle, long molding cycle, large molding shrinkage, poor dimensional stability, brittle crystallization and low heat resistance.
Through the improvement of nucleating agent, crystallizer and glass fiber reinforcement, pet has the following characteristics in addition to the properties of PBT:
1. The thermal deformation temperature and long-term service temperature are the highest among thermoplastic general engineering plastics;
2. Due to its high heat resistance, the Reinforced PET is soaked in a soldering bath at 250 ℃ for 10s, which basically will not deform or change color. It is especially suitable for preparing electronic and electrical parts for soldering;
3. The bending strength is 200MPa, the elastic modulus is 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. Because the price of ethylene glycol used in PET production is basically half cheaper than that of butanediol used in PBT production, PET resin and Reinforced PET are engineering plastics with the lowest price and very high cost performance.
5. Bonding of PET resin: sili-1706 one component room temperature vulcanizate is an elastomer after curing. It has excellent waterproof and shockproof adhesive, and is resistant to high and low temperatures. Because Geli technology is based on the molecular structure of the resin, it is specially used for bonding engineering plastics.
purpose
Glass fiber reinforced pet is applicable to the electronic and electrical and automotive industries, and is used for various coil frames, transformers, televisions, recorder parts and housings, automotive lamp holders, lampshades, incandescent lamp holders, relays, selenium rectifiers, etc. At present, the consumption ratio of PET engineering plastics in several application fields is: 26% for electrical appliances and electronics, 22% for automobiles, 19% for machinery, 10% for appliances, 10% for consumer goods, and 13% for others. At present, the total consumption of PET engineering plastics is by no means large, accounting for only 1.6% of the total pet.
1. Film and sheet: all kinds of food, drugs, non-toxic and sterile packaging materials; High grade packaging materials for textiles, precision instruments and electrical components; Base materials for audio tapes, video tapes, motion picture films, computer floppy disks, metal coatings and photographic films; Electrical insulating materials, capacitor films, flexible printed circuit boards, membrane switches and other electronic and mechanical fields.
2. Application of packaging bottle: its application has changed from the initial carbonated beverage to the current beer bottle, edible oil bottle, condiment bottle, medicine bottle, cosmetics bottle, etc.
3. Electronics and appliances: manufacturing connectors, coil spools, integrated circuit enclosures, capacitor enclosures, transformer enclosures, TV accessories, tuners, switches, timer enclosures, automatic fuses, motor brackets and relays, etc.
4. Auto parts: such as switchboard cover, ignition coil, various valves, exhaust parts, distributor cover, measuring instrument cover, small motor cover, etc. pet's excellent coating, surface gloss and rigidity can also be used to manufacture automotive exterior parts.
5. Mechanical equipment: manufacturing gears, cams, pump shells, pulleys, motor frames and clock parts, and can also be used as microwave ovens, baking pans, various ceilings, outdoor billboards and models
6. The molding processing of PET plastic can be injection molding, extrusion, blow molding, coating, bonding, machining, electroplating, plasma metal plating, printing.
the way to distinguish
1. Smell the taste first. The taste of pet is different from that of ordinary plastics. Burn it with a lighter, and then you will smell a very fragrant and comfortable taste (burn a bottle casually to smell it). If pet contains other ingredients, the taste will be very pungent. One kind of bottle containing SEBS must not be used.
2. Look at the burning part. If it is too dark or oil drops soon, most of the melting points are never normal, which is often found in PET films.
3. Wire drawing: when burning, pull the wire on the lighter to see if the length of the wire is not long. Then pull the wire out and break it. Look at the breakpoint below. The wire is not rolled into a small circle. The more rolled it is, the higher the melting point is.
It's not too common. If it's a bottle, there should never be any big problems. The most critical point is to distinguish whether it contains PVC, which is only the fatal injury of pet. First, take more samples, and then tile it in a sunny place. PVC is light blue in the sun. If there is a white crease in the fold. More than visual identification, limited accuracy, important to see experience.
There is also a more practical and better way. Buy an oven and adjust the temperature to 250 degrees for half an hour. If the goods contain PVC, there will be a lot of yellow spots on the surface; If the melting point is not enough, it will melt soon.
In fact, there are many kinds of pet to be made, such as pet shredded film, pulp block, and roll film with a length of less than 30 cm from foreign factories. These have different customer groups.
The identification of these goods is strongly required to be tested in an oven. In particular, pet reels are a very scarce source of goods in the whole market. Generally, the length is more than 80 to 120 cm, and the price of film with a thickness of 3-5 silk is very high (white and transparent).