Polymers water-repellent fabrics

Early waterproofing treatments consisted of coatings of a continuous layer impenetrable by water. Later water-repellent fabrics permitted air and moisture passage to improve the comfort of the wearer. Aluminum and zirconium salts of fatty acids, siUcone polymers, and perfluoro compounds are apphed to synthetic as well as natural fibers. An increase in the contact angle of water on the surface of the fiber results in an increase in water repeUency. Hydrophobic fibers exhibit higher contact angles than ceUulosics but may stiU require a finish (142). 

Table 10.49 Oil and water repellency of cotton fabrics treated with perfluorinated acrylic polymers [502]...

By varying the nature of the side chain, R, various elastomers, plastics, films, and fibers have been obtained. These materials tend to be flexible at low temperatures, and water and fire resistant. Some fluoroalkoxy-substituted polymers (R = CHXFJ are so water repellent that they do not interact with living tissues and promise to be useful in fabrication of artificial blood vessels and prosthetic devices. 

Ethyl silicate (tetraethoxysilane) is often used without modification as a water-repellent material for concrete and masonry in general. All, or nearly all. the ethoxyl groups are hydrolyzed by the moisture of the air to form cross-linked watcr-rcpcllcnt polymers. The material is applied in desirable thickness, dissolved in some volatile solvent which soon evaporates. Silicone resins which arc partially condensed before application, or even fully condensed, can also be used here. In the latter case, hardness is achieved on evaporation of the solvent. Certain silicone resins arc useful as hydrophobic agents for the impregnation of paper and fabrics. 

Mixtures of the monotriethanolamine titanate and polyols, such as fructose and sorbitol, imparted thixotropic properties to polymer-containing cement (107). A similar reaction of triethanolamine and tetraalkyl titanates previously treated with stearic acid gives the corresponding 1-acyloxytitatranes (108). Aqueous dispersions of these materials can be used to treat fabrics to impart a high degree of water repellency. 

Waterproof Finishes. Waterproofing results from coating a fabric and filling the pores with film-forming material such as varnish, mbber, nitrocellulose, wax, tar, or plastic. The materials may be appHed as hot melts, eg, waxes or some polymers, as solvent solutions, or as aqueous latexes. The continuity of the film provides the water resistance. Except for tents, tarpaulins, and covers, coated fabrics have beenlaigely replaced by plastics, and by fabrics treated with water and oil repellents that do not reduce pemieabiHty to air and water vapor. Fabrics are also commonly laminated to films, such that the total stmcture is waterproof (15), or ia some cases water-resistant but breathable (16). 

A microporous membrane is fabricated from a hydrophobic polymer. As the name implies, the membrane is highly porous (the average pore size is less than 1 /xm) and allows the free passage of gases at the same time, the water-repellent polymer prevents water and solute ions from entering the pores. The thickness of the membrane is about 0.1 mm. 

Ideally, it is easiest to analyse the polymer before application, to prevent any interference by the fabric substrate, adhesives or any finishing processes such as water repellency or colouration by printing. However, this is not practical on the finished coated fabric or laminate. 

Many synthetic fabrics are designed to look and feel like natural polymers but also have the superior properties for which they were designed, such as being wrinkle-resistant, water-repellent, or quick-drying. However, these imitators can t fool a chemist simple tests that can be done in minutes will distinguish the real thing from a pretender. This is because differences in their structures lead to differences in properties. In this experiment, you will identify fabric samples by testing them for characteristic properties. 

Many of the unique properties of silicone oils are associated with the surface effects of dimethylsiloxanes, eg, imparting water repellency to fabrics, antifoaming agents, release liners for adhesive labels, and a variety of polishes and waxes (343). Dimethylsilicone oils can spread onto many solid and liquid surfaces to form films of molecular dimensions (344,345). This phenomenon is gready affected by even small changes in the chemical structure of siloxane in the siloxane polymer. Increasing the size of the alkyl substituent from methyl to ethyl dramatically reduces the film-forming ability of the polymer (346). The phenyl-substituted silicones are spread onto water or solid surfaces more slowly than PDMS (347). 

Nalan . [DuPont] Polymer blends water repellent, extender for fabrics. 

Uses Crosslinking agent, hand builder adding durability and resilience to fabrics (cellulosics, synthetics) adds durability to fluorochem. and water repellent finishes crosslinking agent for hydroxyl-contg. emulsion polymers for top coat systems, waterborne wood finishes, nonwoven binders... 

Hydrophohically finished aramid fabric can be produced by a water-repellant agent. In addition, the application of an antistatic agent is advantageous [35]. The water-repellant agent is a mixture of fluoroacry-late polymers. 

The aim was to understand the molecular mechanisms of water repellency following padding treatment of an initially hydrophilic cotton fabric with an amino-silicone. Knowing as much as possible about the molecular mechanisms should help in designing adequate polymer structures to get the best performance. 

There are other systems, where a prepolymer of low molecular weight reacts with a second component to give a three-dimensional structure and a very durable polymer. Examples include urea and melamine resins used with formaldehyde in fabric finishing, resorcinol/formaldehyde systems used in cord and fabric dips and low-molecular-weight silicones, which react on the subsfiate to give durable water-repellent finishes. 

Ethylene and propylene glycols and their low polymers with the ability to absorb and retain moisture act as softening, plasticizing, and antistatic agents for hydrophilic textile fibers. Treatment with waxes such as paraffin emulsions impart water repellency to cellulose fabrics, but the effect is not permanent. Silicones impart water repellency to all fabrics. 

Z. Shi, I. Wyman, G. Liu, H. Hu, H. Zou, J. Hu, Preparation of water-repellent cotton fabrics from fluorinated diblock copolymers and evaluation of their durability. Polymer 54 (23) (2013)6406-6414. 

These yield polymers suitable for rendering fabrics water repellent with peroxy-acids. In a related reaction, the heterocycles (29) are formed from olefins CF2 CXY (X = F, Y = Cl or CF3 X = Y = Cl) and diethanolamine... 

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