It was shown that an ultrathin continuous fl uoropolymer fi lm that replicates the microrelief of the fi bres forming the fabric is formed on the surface of polyester fabric when it is treated with a solution of a low-molecular-weight fraction of polytetrafl uoroethylene in supercritical carbon dioxide. The protective coating formed is ultrahydrophobic and has extremely low water absorption. An additional increase in the degree of hydrophoby of polyester fabric can be attained by using the chemical method of preliminary modifi cation of the fabric which gives the surface of the polyester fi bres additional roughness.There is an increasing demand for water-resistant textiles on the textile materials market, so that the problem of obtaining household and industrial fabrics with high hydrophoby is pressing. Water-repellent fi nishing of textile materials is to give them the capacity of not being wet with water while retaining air and vapor permeability. The contact angle of wetting -the angle between the tangent to the surface of a drop of liquid at the point of contact of three phases (solid, liquid, and gas) and the surface of a solid, measured inside the liquid phase [2], is the basic index of the hydrophoby of a material, and it should be greater than 90°. Investigators have focused attention on highly hydrophobic -ultra-( > 120°) and superhydrophobic ( > 150°) -materials [3]. The ability of a material with a fl at, smooth, nonporous surface to be wet by liquids is described by Young's equation [2]:where sg is the surface tension on the solid-gas interface; sl is the surface tension on the solid-liquid interface; lg is the surface tension on the liquid-gas interface. A real textile material has a biporous (micro-and macropores) system with a different degree of development. When such materials react with a liquid, it is necessary to take into account the appearance of forces of capillary suction. In this case, the Laplace equation [2], which correlates the capillary pressure (P c ) with the surface tension of the liquid ( lg ) and the average capillary radius (r c ) applies:It follows from Eq. (2) that the capillary pressure will approach zero with no wetting of the capillary walls. It is necessary to consider that Eq. (1) only holds for smooth surfaces, while textile materials are rough. One of two types of wetting takes place on rough surfaces [3]: homogeneous, where the liquid totally fi lls the cavities on the entire surface of the solid, and heterogeneous, where the liquid is in contact with the surface which has cavities totally or partially fi lled with air. For this reason, for describing the effect of roughness on the contact angle of wetting, either Wenzel's equation (3) (for
Surface activation of poly(ethylene terephthalate) fibre materials can be executed by purposeful weak surface hydrolysis and an additional number of carboxyl and hydroxyl groups that have a significant positive effect on the results of applying functional products on the surface of the fibre material is formed in the surface layer of the material as a result. It can be hypothesized that chemically active groups play the role of "anchor" groups, fixing the film of functional products on the surface of the fibres forming the fabric and also ensuring ordering of its structure. A comparison of the efficacy of the activating effect of aqueous and strongly dilute solutions of sodium hydroxide with additives of products made from quaternary ammonium compounds showed that treatment with sodium hydroxide solutions with a concentration of 10-15 g/liter at the boiling point for 10-15 min is the most favorable regime for surface activation of PET fibre material while preserving the initial strength level.One promising way of creating textile materials with special consumer properties is forming an ultrathin layer of functional products on the surface of the elementary fibres. Water-repellent, oil-repellent, acid-resistant, bactericidal, conducting, deodorizing, and other textile materials can be obtained in this way. At the same time, if the problem of strong surface fixation of functional products is relatively simple in modification of most natural fibres, it is very difficult to solve for many popular synthetic fibres, in particular, for poly(ethylene terephthalate) (PET) fibres. The difficulties that arise are related to the chemical inertness of this fibre-forming polymer and the very low number of active groups on the surface of the fibre.However, we know that PET is hydrolyzed at ester bonds in the presence of alkali metal hydroxides, that play the role of catalysts, and the alkaline hydrolysis reaction initially takes place on the outside of the fibre [1-3]. As a result, free hydroxyl and carboxyl groups form on the surface of the material:The appearance of an important number of chemically active groups on the surface of the polymer material is, in our opinion, one of the important conditions of fixation of products on it to give fibre material special consumer properties.
It was shown that solutions of tetrafl uoroethylene telomers in acetone form a coating on the surface of fabric which forms a thin fl uoropolymer fi lm after heat treatment and gives polyester fabrics a high level of water repellency. Methods of acting on the fi bre material that allow additionally increasing the degree of water repellency due to regulation of the thickness and ordering of the fi lm and acting on the microrelief of the fabric were revealed. Preliminary chemical activation of the polyester material and an abrasive effect on its water-repellent coating are proposed for this purpose.Giving textile materials water-repellent properties is an important, widely used method of special fi nal fi nishing. Any textile material, even material consisting of water-repellent synthetic fi bres, has relatively high surface energy that ensures the wettability of its surface with water [1]. To prevent wetting, it is necessary to form a new coating with reduced surface energy on the surface of the fi bres. The generally accepted criterion for assessing water repellency is the contact angle of wetting (the angle between the tangent to the surface of a drop of liquid at the point of contact of three phases -solid, liquid, and gas -and the surface of a solid, measured inside the liquid phase) [2]. For water-repellent surfaces, is greater than 90°. Textile materials with elevated water-repellent properties which have ultra-( > 120°) and superhydrophobic ( > 150°) properties are of special interest [3].Organofl uorine compounds are the most effective for reducing the surface energy of textile materials and consequently increasing the water and dirt repellency and improving the launderability. Nontraditional methods of making polyester fabrics water repellent by using fl uoropolymers were developed by the "Fluoropolymer Materials and Nanotechnologies" consortium. The method of making polyester fabric water repellent by treating it with a solution of ultradisperse polytetrafl uoroethylene in supercritical carbon dioxide is examined in detail in [4,5]. Another promising method of making synthetic fabrics waterrepellent is to form a protective coating on their surface by application of tetrafl uoroethylene telomers from solution in acetone [6]. The features of this method and possibility of increasing its effi cacy are examined in the present study.The product based on tetrafl uoroethylene telomers (trade name Cherfl on) was developed and is manufactured at the Institute of Problems in Chemical Physics (IPCP), Russian Academy of Sciences (Chernogolovka) using radiochemical initiation of polymerization of tetrafl uoroethylene monomers ( 60 Co radiation) [7][8][9]. A mixture of telomers containing more than 90% molecules with an average degree of polymerization of 5-6 and CH 3 -C=O-CH 2 -end groups is formed as a result [7]. The solutions of tetrafl uoroethylene telomers in acetone used in the present study were obtained in a reactor that can maintain a constant concentration of monomer during the reaction [8].
667.027.622:537.525.1 and S. Yu. VavilovaPlasma-chemical modifi cation of polyester thread ensures formation of active hydroxyl and carboxyl groups on its surface, necessary for fi xation of functional preparations whose application on the surface of fi bre material gives it new properties -water-repellent, antimicrobial, deodorizing, etc. A comparison of the effi cacy of plasma-chemical and chemical methods of surface activation of polyester fi bre material shows that in the fi rst case, greater losses of strength are observed in the thread. However, in the case of plasmachemical activation, an additional number of carbonyl/carboxyl groups is formed, which is an important advantage in selecting the method of activating polyester materials.One promising direction in giving the surface of fi bre materials new properties is to modify them by plasma discharge. As a result of plasma treatment, polymer material acquires valuable new properties, in particular, the increased wettability and adhesion necessary for dyeing the surface and using the material as a sorbent. This method advantageously differs from chemical methods of modifi cation [1] by much lower energy losses and shorter process time. Technologies have now been created for modifying polymer materials both with vacuum plasma and with atmospheric pressure plasma, as well as the equipment for their industrial manufacture [2]. However, most industrial methods of plasma-chemical modifi cation of polymer materials are nonselective or weakly selective, which is a serious drawback since the selectivity of the process plays an important role in technologies for modifi cation of textile materials. The method of plasma-solution modifi cation of the surface of fi bre materials, the subject of the present article, is distinguished by the highest selectivity. The high selectivity of plasma-solution treatment of fi bre materials is due to the fact that the active plasma particles entering the solution from a set of secondary particles which react with the surface of the polymer material in milder conditions and as a consequence, more selectively than in the case of "dry" plasma. The plasma-solution modifi cation method also has the following important advantages: -relatively low voltage (0.5-1.5 kV) [3] required for igniting the discharge; -the important possibility of concentrating the low-temperature plasma zone near the surface of the treated sample [4]; -high degree of nonequilibrium of the plasma in the plasma-solution system [5], which allows selecting treatment conditions in which the sample is not destroyed by the thermal effect of the plasma; -migration of the components of the solution into the gas phase [6], which makes it possible to deliberately form the composition of the plasma-forming gas for conducting the treatment.
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