Polyester facts for kids
Polyester is a category of polymers that contain the ester functional group in their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include naturally occurring chemicals, such as in the cutin of plant cuticles, as well as synthetics such as polybutyrate. Natural polyesters and a few synthetic ones are biodegradable, but most synthetic polyesters are not. The material is used extensively in clothing.
Polyester fibers are sometimes spun together with natural fibers to produce a cloth with blended properties. Cotton-polyester blends (polycot) can be strong, wrinkle- and tear-resistant, and reduce shrinking. Synthetic fibers using polyester have high water, wind and environmental resistance compared to plant-derived fibers. They are less fire-resistant and can melt when ignited.
Polyester blends have been renamed so as to suggest their similarity or even superiority to natural fibers (for example, China silk, which is an essentially deceptive term in the textiles industry for a 100% polyester fiber woven to resemble the sheen and durability of insect-derived silk).
Liquid crystalline polyesters are among the first industrially used liquid crystal polymers. They are used for their mechanical properties and heat-resistance. These traits are also important in their application as an abradable seal in jet engines.
Natural polyesters could have played a significant role in the origins of life. Long heterogeneous polyester chains and membraneless structures are known to easily form in a one-pot reaction without catalyst under simple prebiotic conditions.
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Uses
Polyester can be made into thread or yarn. Woven into synthetic fabrics, they are often used to make clothes and home furnishings. These include shirts, trousers, pants, jackets, hats, bedding and upholstered furniture. Polyester fiber is used as cushioning and insulating material in pillows, comforters and upholstery padding. It can be used in curtains to insulate windows and keep heat indoors. Polyester is used to make insulating carpet.
Industrial polyester fibers, yarns and ropes are used in tires, fabrics for their use, and safety belts.
Chemistry
Polyester is a type of polymer that has the ester functional group in its main chain. There are many different polyesters. The term "polyester" as a specific material most often refers to polyethylene terephthalate (PET). Polyesters include chemicals found in nature, such as in plant cuticles. Synthetics made by step-growth polymerization such as polycarbonate and polybutyrate are also polyesters. Natural polyesters and a few synthetic ones are biodegradable, but most synthetic polyesters are not.
The most common polyesters are thermoplastics.
Synthesis
Most polyesters are made with a polycondensation reaction. See "condensation reactions in polymer chemistry". The general equation for the reaction of a diol with a diacid is :
- (n+1) R(OH)2 + n R´(COOH)2 → HO[ROOCR´COO]nROH + 2n pH2O
An alcohol and a carboxylic acid react to form a carboxylic ester. To assemble a polymer, the water formed by the reaction must be continually removed by azeotrope distillation.
Images for kids
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A drop of water on a water resistant polyester
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See also
In Spanish: Poliéster para niños
