Fluorochemical Repellents

Fluorochemical repellents differ from silicone or hydrocarbon-based repellents in several aspects, of which oil repellency is the most important. Fluorocarbons repel both water and oil, whereas repellents with silicone or hydrocarbon hydrophobes repel only water. The ability of fluorocarbons to repel oil is related to their low surface energy. 

The repellency of fluorocarbon finishes depends on the structures of the fluorocarbon segment, the nonfluorinated segment of the molecule, the orientation of the fluorocarbon tail, the distribution and the amount of the fluorocarbon moiety on fibers, and the composition and geometry of the fabric [101]. The relationship between repellency and the structure of the fluorocarbon segment is in accord with the critical surface tension concept developed by Zisman and co-workers (see Chapter 11). Shafrin and Zisman [102] determined the wettabilities and critical surface tensions of t -perfluoroalkyl substituted 77-heptadecanoic acids synthesized by Brace [103]. Once the seven outmost carbon atoms are fully fluorinated x = 7), the wettability of monolayers of the acids F(CF2)a(CH2)i6COOH approaches that of the perfluorocarboxylic acid F(CF2).vCOOH (Fig. 12.2). This suggests that a terminal perfluoroalkyl chain of seven carbon atoms is sufficiently 

The coverage of fiber surfaces by the fluorochemical repellent is a very important variable affecting repellency. Hence, the amount of a fluorochemical needed for maximum repellency depends on the fabric construction (Fig. 12.4) and the structure of the fluorochemical repellent. 

At an equal number of carbon atoms, normal perfluoroalkane chains are more effective than branched chains. Under otherwise identical conditions, a surface comprised of closely packed —CF3 groups has the lowest surface energy and the highest repellency. Pittman and co-workers [105] concluded that polyacrylates containing a perfluoroisopropyl group have a lower critical surface tension than those containing a n-perfluoropropyl group. However, the comparison was made 

The patent literature on fluorocarbon repellents is voluminous. However, most patients disclose variations of nonfluorinated structural features of the repellent molecule. Structural variations of the fluorinated segment are limited by the small number of practical chemical routes to fluorinated intermediates. The most important commercial processes for producing fluorinated intermediates are based on either electrochemical fluorination or telomerization of tetrafluoroethylene (see Chapter 2). 

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Fluorochemicals repel both water and oU because they produce an extremely low energy surface (18—26). The effectiveness of the fluorochemicals depends upon uniform surface coverage and orientation of the molecules on the fiber surface so that the perfluoroalkyl chains are directed away from the surface. The result is a GST as low as 5—10 mN /m (dyne/cm). Fluorochemical finishes are often formulated with nonfluorinated resin-based water-repeUent extenders. These water repeUents not only reduce the cost of the finish but may also improve durabUity (27,28). 

Standard Test 80.7-92). Suppliers of fluorochemical repellents may recommend different times or a different series of hydrocarbons ia the evaluation of treated fabrics. 

Fluorochemicals. Fluorochemicals are the most important class of repellents for textiles. They are the only repellents that provide repellency to water, waterborne stains, oil, oilbome stains, and oily particulates. The various products have a variety of repellency and durabiHty properties for certain fabrics, and the specific compositions ate proprietary. The first company to market fluorochemical repellents was 3M iu the 1950s (Scotchgard Fabric Protector), followed by DuPont (Zepel and Teflon Fabric Protectors). Several other companies such as Autalux Corporation, Ciba Specialties, Eastern Color Chemical, Glo-Tex Chemicals, IVAX Industries, Liadley Laboratories, NICCA U.S.A, Piedmont Chemical, Sedgefield Specialties, Sequa Chemicals, and Yorkshire Pat-Chem also market such finishes (17). Fluorochemical finish appHcation areas include rainwear, upholstery, drapery, and automotive fabrics, roofing materials, and carpeting. Both natural and synthetic textile fibers can be treated. 

Fluorochemical repellents ate commercially available as emulsions or solvent solutions. The most widely used emulsions for fabrics and carpet are cationic, but nonionic emulsions ate becoming mote prevalent. The emulsifier in the formulation can affect the tepeUency and durabiHty of the product (28). Surfactants used in the fluorochemical emulsions or added to finish baths should be nonrewetting and have a minimum adverse effect on oil tepeUency. Solvent solutions of fluorochemicals ate becoming less common as a result of toxicity and environmental concerns. 

To prepare the antimicrobial finish, the samples were padded through baths of 0.5,1 and 2% CTAB solution with wet pick up of 130%, dried at 80-85"c for 3 minutes and cured at 145-150° c for 3 minutes. We also used both the fluorochemical repellent and the antimicrobial agent in one bath. 

The water repellents formulated with waxes and polymers are used as extenders for polymeric fluorochemical repellents. 

De Marco and Dias [20] observed a synergistic effect with pyridinium-type water repellents coapplied with fluorochemical repellents, resulting in a long-lasting protection against rain and a good durability to laundering. This finish was named Quarpel by its inventors. 

Fluorochemicals used in water- and oil-repellent finishes have been monomeric or polymeric. The first fluorochemical repellents used commercially were monomeric. In analogy to repellents with a hydrocarbon hydrophobe (see Section 12.1), perfluoroalkanoic acids, and phosphate esters have been applied as chromium complexes [121-123], zirconium or titanium alkoxides or salts [124-126] or have been converted to quaternary amines [127,128] ... 

The monomeric fluorochemical repellents were superseded by fluoropoly-mers. However, the interest in monomeric fluorochemical repellents is increasing again. Modification of the fiber surface by (1) copolymerization with a fluorinated monomer (e.g., acrylonitrile copolymerized with l//,l/if,2/i/,2i7-heptadecafluo-rodecyl methacrylate [133], (2) adding fluorochemicals to the polymer melt [134-140], or (3) by applying fluorochemicals to preformed fibers [141,142] is being explored and exploited commercially. 

In recent years, fluorochemical repellents have been coapplied mainly with wax dispersions made durable with cross-linking adjuvants. Although a variety of water repellents with hydrocarbon-type hydrophobes enhance the repellency and durability of fluoropolymer repellents, silicones may reduce their oil repellency... 

Fluorochemicals will remain the most effective, durable, and expensive repellents. The use of nonfluorinated extenders, where appropriate, will continue to improve the cost-effectiveness of fluorochemical repellents. Silicones and repellents with hydrocarbon-type hydrophobes will share the market where the perfor-mance/cost relationship is in their favor. 

The mechanisms and kinetics of soiling with liquids differ from those of particulate soil. Soiling with liquid soils is dominated by wetting and wicking processes discussed in Chapter 11. The resistance of fabrics to soiling with a liquid is greatly enhanced by fluorochemical repellents (Section 12.7.)... 

Oil Repellent. Fluorochemicals are the only class of material that can provide oil repeUency without altering the porosity of the paper or paperboard. Physical barriers to oil penetration are used primarily for their moisture- or gas-barrier properties, with retarded oil penetration as a secondary benefit. The most common od-repeUent additives are long-chain perfluoroalkyl phosphate salts of ammonia or diethanol amine. Commercial sources include Scotchban (3M), Zonyl (DuPont), and Lodyne (Ciba Specialties). There are also a fluorochemical carboxylate salt, Lodyne (Ciba Specialties), and fluorochemical copolymers, eg, Scotchban (3M). The widest range of oily fluid holdout is provided by the fluorochemical copolymers. 

It is now opportune to consider the structure-property relationships of fluorochemical finishes in more detail [501,502]. Water repellency depends mainly on reducing the critical surface energy of the fabric surface. This parameter must be less than that of the wetting... 

For application of these fluorochemical finishes to textile fabrics, an extremely important factor is their formulation into suitable aqueous emulsions or dispersions. The quality of the formulation has a critical influence on stability during storage and application, as well as the efficacy of treatment and durability [501,502]. In particular, the choice of surfactant(s) for emulsifying or dispersing must ensure good stability with freedom from deposition on rollers, yet must not impair the water and oil repellency of the finished fabric. No individual product fulfils all requirements hence specifically formulated products are available for certain fibre types. 

Exemplary water-repellent treatments for masonry surfaces include metal stearates, oils, waxes, acrylates (both polymers and monomers), silicones (solvent-based and emulsion), siliconates, silanes and, fluorochemicals. In contrast, to waterproofing coatings, water-repellent coatings, because they are permeable to water vapor, do not trap moisture and, therefore they can reduce spalling. In addition most water-repellent coatings do not alter the appearance of a porous masonry. 

Fluorochemical Stain Repellent and Dry Soil Resistant Finish for Fabrics Aqueous Application... 

CNC AQUAFILM 999 is a mildly cationic fluorochemical oil and water repellent developed specifically for the outerwear market. 

Fluorochemical Stain Repellent Water Repellent Finish for Outerwear,... 

CNC AQUAFILM PA is a new aqueous fluorochemical finish designed to impart lasting high oil and water repellent finishes on outerwear fabrics. Application of this fluorochemical is especially easy because it is completely miscible with cold or warm water. CNC AQUAFILM PA is a one component system which is cationic. Generally, it may be used with any nonionic or cationic additive. Anionic and basic materials have limited compatibility. 

ARIDRY FC Extra is a new aqueous fluorochemical finish designed to impart lasting high oil and water repellence together with dry soil resistance to all fibers including cotton, rayon, wool, nylon, acrylics, polyester and is especially recommended for upholstery fabrics, drapery, slipcovers and other woven materials where dry-soil resistance is of importance. 

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