Last updated on August 10th, 2023 at 12:05 pm
Polyester is defined as a manufactured fibre in which the fibre forming substance is any long-chain synthetic polymer made of at least 85% by weight of an ester of a sub-aromatic carboxylic acid comprising, but not confined to dimethyl terephthalate units and parasols hydroxyl benzoate units.
Physical Properties of Polyester
Polyester filaments and staple fibre are strong due to their crystalline nature. The crystalline nature permits for the formation of highly effective Vander wall’s forces as well as since hydrogen bonds which provided the fibre its good tenacity. The tenacity remains unchanged when wet since the fibre resists the entry of water molecules to a significant extent.
Elastic Plastic Nature
The very crystallinity of the fibre prevents wrinkling and creasing. Repeated stretching and straining causes, distortion of the polymer system as the Vander wall’s forces cannot withstand much stretching.
Filaments and staple fibres are hydrophobic. The lack of polarity and the very crystalline structure resists the entry of water molecules into the polymer system. The hydrophobic nature of the polymer system attracts fats, greases, oils, acid or any other greasy soils. It is believed to be oleophilic. The oleophilic nature makes it not easy to remove grease by soap but by dry-cleaning with organic solvents.
It is a poor heat conductor and it has low resistance to heat. It melts on heating. Polyester textile materials can be permanently heat-set. It is a thermoplastic fibre meaning that it is capable of being shaped or turned when heated. Thermoplastic fibres heated under strictly controlled temperatures soften and can then be made to similar to a flat, creased or pleated configuration. When cooled thermoplastic fibres retain the new configuration.
Chemical Properties of Polyester
Effect of Acids
These polymers are resistant to acids.
Effetc of Alkalis
Alkaline conditions as seen in laundering hydrolyze the ester groups in polyester polymers. The crystalline nature prohibits hydrolysis to a greater extent and it is the surface of filament which gets hydrolyzed. Continued laundering results in hydrolysis and materials get fewer as the surface film of the fibre gets lost.
Effect of Bleaches
It does nor requie bleaching. It retains its whiteness and requires only chlorine bleaches to be used when essential.
It withstands the sun’s ultra-violate radiations and is resistant to acidic pollutants in atmosphere.
It is not easy for dye molecule to penetrate the fibre when dyed, it retains its color after regular wash.
It is resistant to bacteria and other micro-organisms.
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