P, D.T.P, B.Tech
Texport Syndicate (I) Ltd,
Yeshwantpur, Bengaluru - 22


This chapter deals with chemical modification polyester fiber, polyester, appearing in order of their commercial importance to the textile industry. Various approaches used in modification of polyester fibers, modifying agents used, and application of the modified products based on the properties obtained have been highlighted. The information on the various modifications is classified primarily based on the functional properties acquired by the fibers after modification.

Particulars emphasis has been given to the modified polyesters, where in a special section has been included on modifications for better polymerization and faster spinning of the polyester materials. The modification for improved dyeability, differential dyeing, antibacterial properties, reduced flammability, high water absorbency and modified mechanical properties have been discussed for the pet fibers. Several modifications influence combination of properties and hence although they have been discussed under a particular functional property, should be viewed in totality.


Antibacterial, Deep dyeable, Hollow polyester, Hydrophilic, Hydrophobic, Pilling, Soiling


Polyester are polymers made by a condensation reactions taking place between small molecules, in which the linkage of the molecules occurs through the formation of ester groups. Polyesters are commonly made by interaction of a dibasic acid with a dihydric alcohol. This fiber is a medium weight fiber with a density of 1.39g/cm3. Compared with nylon, polyester are rather heavy fibers, for this reason polyester textile materials are manufactured as light weight or thin fabrics. The most common polyester apparel filament or stable fiber is usually composed of polyethylene terepthalate (PET) polymers.


The modified polyester are prepared to overcome some of drawbacks such as low moisture regain, static electricity and soiling problems, this three drawbacks are interrelated and associated with hydrophobicity of the polyester. By making hydrophilic these drawbacks can be overcome.

Thus, a hydrophilic fiber will have a higher moisture regain. The garments made up of hydrophilic fiber will absorb perspiration and will be comfortable.

Another drawback is pilling problem and very difficulty in dyeing. The low pilling fibers are required to retain the elegant appearance of polyester garments for a long time. These low pilling fibers have lower tenacity than normal polyester fibers. Thus, although pills are formed in these fabrics, these pills are removed by simple brushing or washing.


Polyester fibers were latecomers among manufactured fibers, and had to find their way into a market where polyamide and acrylic fibers were already established. Polyester fibers used for textile application, offers langible benefits to both processors and consumers. Low denier fibers blended with cotton gave higher strengths at lower twist levels, than found in 100% cotton yarns. The characteristic property of the polyester was immediately encased by the designers of shirt and blouse fabrics. Polyester fibers provided textiles with a dimensional stability, wear resistance and easy care properties with the handle, drape and appearance being preserved for longer periods than in fabrics made form natural fibers.

High rate of growth of polyester fibers is due to their outstanding physical properties, chemical resistance, easy properties, and resistance to moth, mildew and microorganism. In spite of its outstanding performance, there are some shortcomings in PET, for example.

» Hydrophobic nature
» Ease of soiling
» Static charge build up
» Tendency to pill
» Lack of dye receptor sites in the polymer chain.