Deweighting, deweighing or weight reduction, is a chemical treatment that peels the surface of

polyester Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include natural ...

fibers and makes them softer and finer. It also reduces the

fiber Fiber or fibre (from la, fibra, links=no) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate ...

weight and hence weakens the strength. Additionally, the treatment enhances the absorbency of the treated substrates. Deweighting is an alkaline hydrolysis treatment that affects the surface fibers of the polyester and reduces the decitex or denier of fibers, weight loss of between 10% and 30% is possible during the treatment. Polyester and

cotton Cotton is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus ''Gossypium'' in the mallow family Malvaceae. The fiber is almost pure cellulose, and can contain minor perce ...

blends can be treated with an

alkali In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a ...

process to make them look and feel like

silk Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from the coc ...

Process of deweighting

When

Sodium hydroxide Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly caustic base and alkali ...

(5~10 grams per litre) is applied to polyester in hot conditions, the chemical reaction peels off the surface of the polyester fibers and changes the surface of the finished product, making it softer and finer in texture. During treatment, it is necessary to consider the loss of strength and the degree of softness. Treatment may be carried out by the exhaust method in a dyeing vessel such as an overflow, HT, or

winch dyeing machine A Winch machine or winch dyeing machine is a type of dyeing machine suitable for piece dyeing. A winch is a simple machine. It is equipped with a winch to guide the fabric from the vat. It has a straight front and a curved back. Long lengths are ...

. The addition of a cationic accelerator and the use of a HT (high temperature) vessel can accelerate the alkalization process. Finally, an anionic surfactant is applied to prevent further deweighting and to aid in the dispersion of the peeled fibers.

Alkali deweighing of polyester

Alkali deweighing treatment of polyester fiber is a complicated process that includes treatment with caustic at a hot temperature. The hydraulic action peels the surface, resulting in a weakening of the fiber and an increase in its softness and fineness. Hence, care should be taken while treating. The deweighting rate of the fabric can be changed by manipulating the temperature and time. Alkali deweighting of polyester fiber with imidazole ionic liquid is helpful in accelerating the deweighing action. The processing with imidazole ionic liquid can improve alkali deweighting efficiency and increase alkali agent usage rate while using less alkali agent.

One-bath alkali deweighting and dyeing process

Deweighting and simultaneously dyeing with disperse dye is also possible, which avoids the two-step process of deweighting and then dyeing in another bath.

Bicomponent

Alkali deweighting of bicomponent containing

polytrimethylene terephthalate Polytrimethylene terephthalate (PTT), is a polyester synthesized and patented in 1941. It is produced by a method called condensation polymerization or transesterification. The two monomer units used in producing this polymer are: 1,3-propanedio ...

polyamide 6 Nylon 6 or polycaprolactam is a polymer, in particular semicrystalline polyamide. Unlike most other nylons, nylon 6 is not a condensation polymer, but instead is formed by ring-opening polymerization; this makes it a special case in the comparis ...

separates the PTT and nylon components of the yarns, resulting in superfine filaments with a change in fiber diameter and shape.

References

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