Polyethylene terephthalate is the most common thermoplastic polymer resin of the polyester family and is used in fibers for clothing, containers for liquids and foods, thermoforming for manufacturing, and in combination with glass fiber for engineering resins.
It may also be referred to by the brand name Dacron.
1. PET in its natural state is a colorless, semi-crystalline resin.
2. PET can be semi-rigid to rigid, and it is very lightweight. It makes a good gas and fair moisture barrier, as well as a good barrier to alcohol and solvents.
4. It is strong and impact-resistant.
5. PET becomes white when exposed to chloroform and also certain other chemicals such as toluene.
Polyethylene terephthalate is produced from ethylene glycol and dimethyl terephthalate (C6H4(CO2CH3)2) or terephthalic acid. Dimethyl terephthalate process:
Polyesterification reaction in the production of PET.
In dimethyl terephthalate process, this compound and excess ethylene glycol are reacted in the melt at 150–200 °C with a basic catalyst. Methanol (CH3OH) is removed by distillation to drive the reaction forward. Excess ethylene glycol is distilled off at higher temperature with the aid of vacuum. The second transesterification step proceeds at 270–280 °C, with continuous distillation of ethylene glycol as well.The reactions are idealized as follows:
C6H4(CO2CH3)2 + 2 HOCH2CH2OH → C6H4(CO2CH2CH2OH)2 + 2 CH3OH
n C6H4(CO2CH2CH2OH)2 → [(CO)C6H4(CO2CH2CH2O)]n + n HOCH2CH2OH
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium in the family of Malvaceae. The fiber is almost pure cellulose. Under natural conditions, the cotton bolls will tend to increase the dispersion of the seeds.
• Gossypium hirsutum
• Gossypium barbadense
• Gossypium arboreum
• Gossypium herbaceum
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