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About 60% crystallization is the upper limit for commercial products, with the exception of polyester fibers. [ clarification needed ] Transparent products can be produced by rapidly cooling molten polymer below the glass transition temperature (T g ) to form a non-crystalline amorphous solid . [ 34 ]
The onset of thermal degradation dictates the maximum temperature at which a polymer can be used. It is an important limitation in how the polymer is manufactured and processed. For instance, polymers become less viscous at higher temperatures which makes injection moulding easier and faster, but thermal degradation places a ceiling temperature ...
The heat distortion temperature is determined by the following test procedure outlined in ASTM D648. The test specimen is loaded in three-point bending in the edgewise direction. The outer fiber stress used for testing is either 0.455 MPa or 1.82 MPa, and the temperature is increased at 2 °C/min until the specimen deflects 0.25 mm.
Polyester resins are synthetic resins formed by the reaction of dibasic organic acids and polyhydric alcohols. Maleic anhydride is a commonly used raw material with diacid functionality in unsaturated polyester resins. [1] Unsaturated polyester resins are used in sheet moulding compound, bulk moulding compound and the toner of laser printers.
Polycyclohexylenedimethylene terephthalate (PCT) is a thermoplastic polyester formed from the polycondensation of terephthalic acid and cyclohexanedimethanol. [1] Its chemical structure is similar to that of polyethylene terephthalate (PET), with which it shares properties like dimensional stability and chemical resistance.
Polyester has high glass transition temperature T g and high melting point T m, good mechanical properties to about 175 °C, good resistance to solvent and chemicals. It can exist as fibers and films. The former is used in garments, felts, tire cords, etc.
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A polyester shirt Close-up of a polyester shirt SEM picture of a bend in a high-surface area polyester fiber with a seven-lobed cross section A drop of water on a water resistant polyester Polyesters can contain one ester linkage per repeat unit of the polymer, as in polyhydroxyalkanoates like polylactic acid , or they may have two ester ...