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. 

The test methods can be divided into three main classes [157,158]  

Class I. Spray tests to simulate exposure to rain 

Class II. Hydrostatic pressure tests to measure the penetration of water as a function of pressure exerted by water standing on the fabric 

Class III. Sorption of water by the fabric immersed in water 

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Repellents Tested with an Inanimate Attractant. Machines have been constmcted by several groups to measure the intrinsic (initial) repeUency of a compound when it is added to a warm, moist airstream to overcome the attractiveness of the airstream to mosquitoes. Such machines remove the factor of human odor ia attempts to simplify the measurement of repeUency. 

Repellents Tested with Animal Attractants. Numerous methods have iavolved the use of animals as attractants, foUowed by evaluation of repeUents as skin treatments or attached cloth treatments, often against crawling arthropods such as fleas, ticks, and mites. Animals such as gerbUs, guiaea pigs, camels, mice, shaved rabbits, and hairless dogs have been used, particularly when the toxicity is unknown. 

Townsend s vole Feeding in presence Avoids repellent Test without Merkenseta/.,... 

Repellency Tests. To determine the repellency of treated cloth, equal size patches of treated and untreated cloth were suspended in a laboratory hood and given equally timed sprays of emulsified chemical. This treatment was reproducible to plus or minus 10% using the time application at a given pressure. 

In the repellency test (Table III), chlorpropham showed a much higher deposition on the treated cloth than the other chemicals tested. However, in this particular test of penetration while it is higher than other chemicals the percent penetrating, in comparison with the surface deposit, is small. The treatments seemed to be effective for both PCP and 2,4,5-T isooctyl ester. 

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. 

Repellent test for squirrels (a) setup of grid of acorns near trees that provide refuge for the squirrels (b) squirrels approaches for another acorn and (c) consumption of an acorn. Note how repeated visits by squirrels have not disturbed the arrangement of the acorns, (d) Circular arrangement of acorns... 

Repellence tests with essential oils at 90% concentration indicated that five essential oils were effective repelling mosquitoes for 90 min (Table III). The essential oil of Acantholippia seriphioides was repellent even at the lowest concentration tested (12.5%). Repellence by this essential oil was expected because its main components are p-cymene (53%) and thymol (47%), both components showed repellent activity for approximately Ih against mosquitoes species (46). At concentrations of 12.5%, Aloysia citriodora, Baccharis spartioides and Rosmarinus officinalis showed the longest repellency times. Comparisons of the principal components of each essential oil suggest that limonene and camphor were the main components responsible for the repellent effects (46). 

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. 

The lubricating and repellent test liquids must be immiscible. 

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

In conjunction with repellency tests, the air permeability and the water-vapor permeability (ASTM D 737-96 DIN 53 887) [153b] of a fabric are sometimes determined. Water-vapor transmission properties of a fabric are important variables affecting wearing comfort of repellent garments [173]. 

S. B. Ogoma, S. J. Moore, and M. F. Maia, A systematic review of mosquito coUs and passive emanators Defining recommendations for spatial repellency testing methodologies, Parasit. Vectors, 5, 287, 2012. 

With a satisfactory ANN model, structures can be devised and tested in the model to predict their repellent classes. This was performed with just over 2000 acylpiperidine structures. Some of these compounds were tested previously, but many others were novel in that they were not evaluated previously as mosquito repellents. From 2000 predicted compounds, 34 were selected for synthesis of them, 23 were novel compounds and 11 were chosen from those in the USDA archive. Selection of compounds tested previously allowed for comparison and validation of the current repellent testing methodology with that used decades ago. The repellency data generated for this study were more precise and linear, that is, the repellency was measured in days of protection, rather than put... 

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