Types
Polyesters as thermoplastics may change shape after the application of heat. While combustible at high temperatures, polyesters tend to shrink away from flames and self-extinguish upon ignition. Polyester fibers have high tenacity and E-modulus as well as low water absorption and minimal shrinkage in comparison with other industrial fibers.
Unsaturated polyesters (UPR) are thermosetting resins. They are used as casting materials, fiberglass laminating resins and non-metallic auto-body fillers. Fiberglass-reinforced unsaturated polyesters find wide application in bodies of yachts and as body parts of cars.
According to the composition of their main chain, polyesters can be:
| Composition of the main chain | Number of repeating units | Examples of polyesters | Examples of manufacturing methods |
|---|---|---|---|
| Aliphatic | Homopolymer | Polyglycolide or Polyglycolic acid (PGA) | Polycondensation of glycolic acid |
| Polylactic acid (PLA) | Ring-opening polymerization of lactide | ||
| Polycaprolactone (PCL) | Ring-opening polymerization of caprolactone | ||
| Copolymer | Polyethylene adipate (PEA) | ||
| Polyhydroxyalkanoate (PHA) | |||
| Polyhydroxybutyrate (PHB) | |||
| Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) | Copolymerization of 3-hydroxybutanoic acid and 3-hydroxypentanoic acid, butyrolactone and valerolactone (oligomeric aluminoxane as a catalyst) |
||
| Semi-aromatic | Copolymer | Polyethylene terephthalate (PET) | Polycondensation of terephthalic acid with ethylene glycol |
| Polybutylene terephthalate (PBT) | Polycondensation of terephthalic acid with 1,4-butanediol | ||
| Polytrimethylene terephthalate (PTT) | Polycondensation of terephthalic acid with 1,3-propanediol | ||
| Polyethylene naphthalate (PEN) | Polycondensation of at least one naphthalene dicarboxylic acid with ethylene glycol | ||
| Aromatic | Copolymer | Vectran | Polycondensation of 4-hydroxybenzoic acid and 6-hydroxynaphthalene-2-carboxylic acid |
Increasing the aromatic parts of polyesters increases their glass transition temperature, melting temperature, thermal stability, chemical stability...
Polyesters can also be telechelic oligomers like the polycaprolactone diol (PCL) and the polyethylene adipate diol (PEA). They are then used as prepolymers.
Read more about this topic: Polyester
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