PET plastic is the abbreviation of polyester terephthalate, abbreviated as pet or PETP. It mainly includes pet and PBT. Polyethylene terephthalate is also known as polyester resin. It is a condensation polymer of terephthalic acid and ethylene glycol, together with PBT, collectively known as thermoplastic polyester, or saturated polyester.
The molecular structure of pet plastics is highly symmetrical, and it has a certain ability of crystal orientation, so it has high film-forming and forming properties. Pet plastics have good optical properties and weatherability. Amorphous pet plastics have good optical transparency.
In addition, pet plastics have 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 is similar to that of pet, and most of its properties are the same. However, the main chain of PBT is changed from two methylene groups to four, so the molecules are more flexible and the processability is better.
Pet is an opalescent or light yellow highly crystalline polymer with smooth and glossy surface. It has good creep resistance, fatigue resistance, friction resistance, low wear and high hardness, and has the largest toughness in thermoplastic plastics; it has good electrical insulation performance, little influence by temperature, but poor corona resistance. Non toxic, weather resistant, chemical resistant, good stability, high moisture absorption, drying before molding is necessary. It is resistant to weak acids and organic solvents, but not to hot water immersion and alkali.
PET resin has high glass transition temperature, slow crystallization rate, long molding cycle, large molding shrinkage, poor dimensional stability, brittle molding and low heat resistance.
With the improvement of nucleating agent, crystallizer and glass fiber, pet has the following characteristics besides PBT
1. The hot deformation temperature and long-term service temperature are the highest among the general engineering thermoplastics;
2. Because of its high heat resistance, the Reinforced PET can be immersed in 250 ℃ solder bath for 10s, which can hardly deform or change color, so it is especially suitable for the preparation of electronic and electrical parts for tin soldering;
3. The bending strength is 200MPa, the elastic modulus is 4000mpa, the creep and fatigue resistance are also very good, the surface hardness is high, and the mechanical properties are similar to those of thermosetting plastics;
4. Because the price of ethylene glycol used in PET production is almost half as much as that of butanediol used in PBT production, the price of PET resin and Reinforced PET are the lowest among engineering plastics, and have high cost performance ratio.
5. Bonding of PET resin: sili-1706 one component room temperature vulcanizate is an elastomer after curing. It has excellent waterproof and shockproof adhesive. It can resist high and low temperature. Because of the research on molecular structure of resin, sili-1706 is specially used to bond engineering plastics.