Polyethylene terephthalate is the most important variety of thermoplastic polyester. Its English name is Polythylene terephthalate, or PET or PETP (hereinafter referred to as PET), commonly known as polyester resin. It is a polycondensation of terephthalic acid and ethylene glycol. Together with PBT, it is called a thermoplastic polyester, or a saturated polyester. PET is a highly crystalline polymer of milky white or light yellow, with smooth and glossy surfaces. It has the characteristics of creep resistance, fatigue resistance, friction and dimensional stability, small abrasion and high hardness, and has the greatest toughness in thermoplastics. It has good electrical insulation performance and little impact on temperature, but it has poor corona resistance. Non-toxic, resistant to climate, good stability of anti chemical drugs, low water absorption, weak acid and organic solvents.