Water repellency tests

A variety of water-repellency tests have been developed and used over the years. The limitation of space permits description of only the most widely used tests. The reader is referred to reviews by Nonis [152] and Lewedag [153] and papers published by Slowinske [154-156] for more information on the testing of water-repellent finishes. 

Table 12.4 Water-Repellency Tests Simulating Exposure to Rain...

The results of this test demonstrated that the diamides of the Ci4 and higher saturated fatty acids were water repellents. On the other hand, the unsaturated oleic acid derivatives enhanced hydrophilicity. 

TABLE 2. Water Repellency and Water Slip Testing Results for Selected Polymers"... 

AATCC methods for determining water repellency are AATCC 22 (spray test) and AATCC 70 (tumble jar dynamic absorption test). In the spray test, water is sprayed against the taut surface of the test specimen to produce a wetted pattern the size of which depends on the repellency of the fabric. Evaluation is by comparing the pattern with a series of patterns on a standard chart. The latter method evaluates the percentage by weight of water absorbed by a sample after dynamic exposure to water for a specified period of time. 

Oxadiazole derivatives have been tested in the textile industry as antistatic agents for textile finishes,232,233 thermally stable polymers,82, 234,235 fluorescent whiteners,236 oil and water repellents on cotton and wool,237 and blue dyes for polyesters and polyamides.238 Oxadiazole merocyanine dyes have been patented as photosensitizers for silver halide emulsions.239... 

Semi-quantitative results may be obtained by the use of the Yagoda confined-spot-test papers (Schleicher and Schuell, U.S.A., Nos. 211Y and 597Y) these are prepared with a chemically inert, water-repelling barrier which constricts the spot reaction to a uniform area of fixed dimensions. 

TABLE 1. Water/alcohol and oil repellency testing of fabrics modified with perfluoroacrylate monomer to confer a hydrophobic/oleophobic repellent surface. 

Fabric Sample Water/Alcohol Unwashed Repellency Test 10 Wash Cycles Oil Repellency Test ... 

TABLE 3. Results of water and methylene/iodine repellency testing of polyimide films obtained by reacting 1,2,3,4-cyclobutane tetracarboxylic dianhydride with amines described in Table 1. 

CONDENSOL II protects coloured goods from any loss of rub fastness caused by water-repellent finishing. CONDENSOL II is affected by metal salt. If fairly large quantities of cross-linking agent and catalyst are to be used, preliminary trials should always be carried out to test whether the bath stability is adequate. 

Water-repellent fabrics resist wetting or repel waterborne stains they pass AATCC Test Method 22 (Spray Test). 

The levels of water repellency required to pass the preceding tests depend upon the specifications for particular fabrics. 

Test Methods. The test methods used for water or oil repellency ate quite varied, in accordance with paper or paperboard type and end use. Two tests commonly used to measure water repellency, the Hercules Size Test and the COBB Test, as well as others have been summarized (55,69,70). 

After eight years of exposure, an extensive examination was started in 1994 to evaluate the effectivity and durability of the water repellent treatments [4]. Macroscopic tests as water uptake measurements were carried out to determine the remaining effect of the protective organosilicon layer. Due to the fact that surface information from hydrophobic treatment of mineral surfaces is supplied by surface sensitive measuring techniques, TOF-SIMS and additional DRJFT-studies on treated and exposed material were performed. 

Naturally, leather absorbs some liquid water but mainly is water resistant. The leather industries do not claim that it is waterproof. So-called waterproof leathers are finished with water repellent agents such as organo-silicon, fluorocarbon and so on. Water absorption of leather can be tested by a static absorption method (ASTM D1815, 2000a). Cut the conditioned specimen with a circular cutter. Measure the diameter and thickness of the specimen. Calculate its volume in cubic centimetres. Weigh the specimen to the nearest 0.01 g. Immerse the specimen in distilled water at 23 1 °C in ahorizontal position with the grain side up. Leave the specimen immersed for a period of 30 min. At the end of immersion, take out the specimen and blot the surface of the specimen with filter paper to remove excess water. Weigh the specimen immediately to the nearest 0.01 g. Calculate the amount of water absorbed by the specimen ... 

INDA, the Association of the Nonwoven Fabrics Industry, has published repellency test methods specifically designed for the nonwoven fabric structure. 1ST 80.5(01/ is designed to measure a nonwoven material s abihty to resist gravity-only penetration by a saline solution. This property is useful in assessing the degree of water repeUency needed by nonwovens in a number of applications. A sample of the nonwoven to be tested is placed in the mouth of a quart size Mason jar containing saline solution. The jar is then inverted and placed on an electric grid that senses when the solution has penetrated the nonwoven. The time to complete penetration is recorded as a measure of repellency. 

Another INDA repellency test especially useful for nonwovens intended for medical use is 1ST 80.8(01). This test is similar to AATCC 118 in that a series of liquids with varying surface tensions are placed dropwise on the sample to determine at what point the nonwoven is wetted. The difference in this test is that the liquids used are composed of varying concentrations of alcohol and water from 100% water (rating 0) to 100% alcohol (rating 10). Methanol, ethanol and isopropanol may be used as the alcohol component. The higher the rating, the higher the level of repellency of the nonwoven. 

AATCC Test Method 22-2001, Water repellency spray test . Technical Manual of the American Association of Textile Chemists and Colorists, Research Triangle Park, American Association of Textile Chemists and Colorists, 2003, 65-67. 

ISO 9865 1991, Textiles, Determination of Water Repellency of Fabrics by the Bundesmann Rain Shower Test, International Standards Organization, Geneva, 1991. 

Cotton fabrics and cotton/polyester blend fabrics were treated in different finishing baths containing water repellent only, water repellent and a biocidal precursor (dihydro xymethyl-5,5-dimethylhydantoin, DMDMH), or DMDMH only. The antibacterial efficiency of the treated fabrics was tested against Staphylococcus aureus and Escherichia coh. Fabrics treated with water repellent only showed no antibacterial efficiency, whereas those treated with DMDMH either with or without water repellent showed excellent antibacterial efficiency. 4 refs. 

The oil can also be extracted from water using an oil-absorbing and water-repelling solid. The oil is then analyzed from this substrate by a variety of means, including measuring the amount of light absorbed in certain selected narrow bands. Still another method is to use enzymes that are selectively affected by some of the oil s components. A test kit that uses colour to indicate the effect of the oil on the enzymes is available. 

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. 

Galbraith et al [20] compared cotton, water repellent cotton, and acrylic garments through wearing tests and concluded that the major factor causing discomfort was the excess amount of sweat remaining on the skin surface. Niwa [21] stated that the ability of fabrics to absorb liquid water (sweat) is more important than water vapour permeability in determining the comfort factor of fabrics. 

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