Effect of alkali on filaments of poly(ethylene terephthalate) and its copolyesters

Abstract

SynopsisT h e alkali hydrolysis of poly(ethy1ene terephthalate), anionic copolymer of poly(ethy1ene terephthalate), and block copolymer of poly(ethy1ene terephtha1ate)-poly(ethy1ene glycol) is investigated under a variety of conditions of alkali concentration in aqueous bath, additives, time, and temperature. Measurements of loss in weight, linear density, breaking load, tenacity, elongation to break apart from intrinsic viscosity, fiber density, COOH-end group content, diameter of filaments, and scanning electron micrographs have been analyzed to identify the differences in the action of alkali on these polymer materials.

Surface structure and properties of poly-(ethylene terephthalate) hydrolyzed by alkali and cutinase

“…A weight loss of <1 w% was recorded for PET-Cr films treated with 1 M NaOH at 40 min. This value is in agreement with previously reported results [4]. A 2 h treatment was the limit time for the PET-Am film.…”

“…This confirms previous observations that alkali or cutinase treatments change the surface properties of PET films while leaving the bulk properties unchanged [4,23], or inducing only very small changes [22]. On the other hand, the trend of the WCA values shown in Fig.…”

“…It is widely recognized that the alkaline attack is confined to the PET surfaces exposed to the liquid, because highly ionized compounds like aqueous sodium hydroxide are not allowed diffusing too much into the bulk due to the strongly non-polar environment of PET. A peeling mechanism has been proposed by which alkali attacks PET chains (preferentially from the end groups) and removes hydrolyzed PET material, thus leading to the formation and exposition of new surfaces [4]. This mechanism seems to be confirmed by the progressive weight loss and decrease in size of PET fibres, which are accompanied by the negligible changes in the degree of polymerization and crystallinity, and in the ultimate tensile performance of alkali-treated PET fibres.…”

“…The different mechanism by which alkali and cutinase hydrolyze PET can probably explain the higher degree of surface order and crystallinity achieved by PET-Am films treated with cutinase. Alkali preferentially attacks the surface of PET by hydrolyzing ester bonds from the chain ends, thus shortening chains and removing hydrolyzed PET material by the peeling mechanism [4]. Depending on treatment conditions, variable extents of weight loss are usually recorded and the typical pitted aspect can be observed on the surface of PET upon alkaline treatment.…”

Discussion on Avoidance of Staining Problem in Cotton/CDPET Dyeing

“…Again, the hydrolysing of this modified polymer takes place more readily as it is highly sensitive to heat setting. A comprehensive research has been undertaken on CDP [6][7][8] as a result of the brilliant colour that the dyed fabric displayed and higher colour yield, as well as better wet and sublimation fastnesses and the rest. The application of cationic dyes has been successfully performed at 100 o C and normal pressure on easy cationic dyeable polyester (ECDP) while the dyeing of blends made up of comprising ECDP and cellulosic or protein fibres could be accomplished without damaging the fibres [9].…”