Modification of the surface of poly(ethylene terephthalate) fabrics by application of a water-repellent coating in supercritical carbon dioxide medium

Abstract

It was shown that in treating PET fibre materials with a solution of ultradisperse, low-molecular-weight polytetrafluoroethylene in supercritical carbon dioxide, an ultrathin layer of fluoropolymer that gives the fabric a high degree of water repellency is formed on the surface.Due to the high demand for water-repellent textile materials for industrial and household applications, the problem of manufacturing stable and strong water-repellent coatings on widely used poly(ethylene terephthalate) (PET) materials is pressing. Despite the hydrophoby of PET fibres, the textile materials made from them cannot retain drops of liquid on their surface. Liquid instantaneously passes through the fabric due to forces of capillary suction of the complex fibres. PET materials have surface energy which is excess for the liquids in contact with them during use.To give PET textile materials stable unwettability, their surface energy must be significantly reduced. To do this, it is necessary to apply a substance whose hydrophobic sections are oriented to the outside area on each fibre without overlapping the micropores of the textile. A new outer surface with low surface energy is formed in this way.Water repellents are used in practice to manufacture fabrics with water-repellent properties, and effective textile auxiliaries based on fluorinated hydrocarbons are very popular [1]. However, the effect obtained with these preparations is not sufficiently stable, especially on synthetic fabrics. This is because the preparations based on fluorinated hydrocarbons are insoluble in water and are thus applied from emulsions and dispersions. They form weakly bound, thick, condensed layers on the surface of synthetic fibres which are easily washed off in laundering and dry cleaning and are rubbed off as the fabric is used.Attempts have been made to improve the composition of the product to eliminate this drawback. In particular, one of the world leaders in developing and manufacturing products for the textile chemistry, the Swiss firm Clariant, is offering a new series of fluorine-containing products for hydro-and oleophobic finishing -the Nuva group of products [2]. These products ensure that fabrics of different composition are given excellent oil-and water-repellent properties. However, the products are used in high concentrations (for synthetics, 10-30 g/liter) [2] and are very expensive. In addition, the inadequate resistance of the effect attained to the effects of use persist, since the water repellents are also applied from emulsions or dispersions.This drawback can be eliminated by applying a water-repellent substance from natural solution. In this case, it is no longer necessary to use specially synthesized complex products based on polymer compositions of fluorinated hydrocarbons containing emulsifiers. An additional advantage of stopping use of complex water-repellent products containing cationactive emulsifiers is reducing the tendency of the water-repellent textile material toward dry soiling. An industrially manufactured fluori...

Analysis of a polytetrafluoroethylene coating deposited onto polyester fibers from supercritical carbon dioxide

“…In the absorption spectrum of the treated fabric, there is a weak band at 1203 cm -1 and a pronounced band at 1147 cm -1 (Fig. 1), indicative of the presence of the fl uoropolyner on the fabric surface.Our results are confi rmed by those of the previously made X-ray diffraction analysis [18], which showed the presence of PTFE on the fi ber as a separate phase.As already noted, the modifi cation involves a decrease in the surface energy of the material. To make the material stably hydrophobic, oleophobic, and superhydrophobic, the surface energy should be decreased to 40, 20, and 10 mJ m -2 , respectively [21][22][23].…”

Ensuring a high degree of water repellency of polyester textile materials by treating them with supercritical carbon dioxide

“…However, the amount of polytetrafl uoroethylene applied on the substrate changes insignifi cantly -from 0.5 to 0.96 g/m 2 . The coating formed probably replicates the microrelief of the substrate, smooth for the polyester fi lm and rough for the fabric [7], and this also explains the much higher appearance of a water-repellent effect in the treated fabric.…”

“…New principles for nontraditional technologies to make polyester fabrics water repellent were developed as a result of the studies conducted by the "Fluoropolymer Materials and Nanotechnologies" Consortium [5][6][7][8]. We will focus special attention on an analysis of the causes of attaining a high degree of water repellency and revealing the basic process factors which can be acted on to increase the water repellency of polyester fabrics to the ultra-and even the superlevel.…”

“…The fi lm is applied from a solution of ultradisperse polytetrafl uoroethylene (Forum) in supercritical carbon dioxide (SC-CO 2 ) [7]. Forum, developed at the Institute of Chemistry, Far East Branch, Russian Academy of Sciences, is the product of thermal gas-dynamic degradation of industrial polytetrafl uoroethylene.…”

“…The lowmolecular-weight fraction of Forum is readily soluble in supercritical carbon dioxide [9,10]. Spontaneous deposition of the polytetrafl uoroethylene fi lm on the poly(ethylene terephthalate) substrate, which was a polyester fi lm 15 m thick or polyester suit fabric, is based on deliberately decreasing the solubility of the low-molecular-weight fraction in SC-CO 2 by reducing the pressure and/or the temperature in the system [7].…”