Polyester :
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 occurring chemicals, such as in the cutin of plant cuticles, as well as synthetics through step-growth polymerization such as polybutyrate.
The main raw materials:
- Purified terephthalic acid (PTA) or 1,4
benzenedicarboxylic acid,
- Dimethylterephthalate
(DMT) or1,4 benzenedicarboxylic acid dimethyl ester
- Mono Ethylene Glycol
(MEG) or 1,2 ethanediol
Production of Polyester:
Synthesis of polyesters is generally achieved by a poly condensation reaction. The general equation for the reaction of a diol with a diacid is :
Synthesis of polyesters is generally achieved by a poly condensation reaction. 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 H2O
Aliphatic polyesters can be assembled from lactones under very mild conditions, catalyzed anionically, cationically or metallorganically. A number of catalytic methods for the
copolymerization of epoxides with cyclic anhydrides have also recently been
shown to provide a wide array of functionalized polyesters, both saturated and
unsaturated.
Importance of Polyester:
1.
The relatively easy accessible raw materials PTA or
DMT and MEG
2.
The very well understood and described simple chemical
process of polyester synthesis
3. The low toxicity level of all raw materials and side
products during polyester production and processing
4.
The possibility to produce PET in a closed loop at low
emissions to the environment
5.
The outstanding mechanical and chemical properties of
polyester
6.
The recyclability
7.
The wide variety of intermediate and final products
made of polyester.
Uses of Polyester:
1. Polyester fiber is used as cushioning and insulating material in pillows, comforters and upholstery padding.
2. Polyesters are also used to make bottles, films, tarpaulin, canoes, liquid crystal displays, holograms, filters, dielectric film for capacitors, film insulation for wire and insulating tapes.
3. Polyesters are widely used as a finish on high-quality wood products such as guitars, pianos and vehicle/yacht interiors.
To be continue........
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