Fiber friction

Fiber friction can be deterrnined by physical methods. For rapid evaluation of fiber or yam friction, the capstan method is used, where a yam or fiber is pulled over a cylindrical surface. The frictional coefficient, ]1, can be determined according to the formula... 

Methods for determining fiber-to-fiber friction have been developed (29—31). The friction coefficient can also be measured in terms of the force required to pull entwined fibers apart (32—34) or the force necessary to remove a single fiber from a mass of fibers under pressure (35). Another test involves an apparatus wherein one or a series of parallel fibers are mounted across a small bridge similar to a violin bridge. This is then pressed against a surface that may be another fiber or some other material, and the fibers alternately sHp and stick as they sHde across each other (36,37). 

Because fiber frictional properties are so important in the conversion of staple yams to spun yams, ASTM D2612 has been designed to measure the cohesive force encountered in the drafting or fiber alignment of sHver and top under static conditions. This frictional force is affected by surface lubrication, linear density, surface configuration, fiber length, and fiber crimp. 

Control of fiber friction is essential to the processing of fibers, and it is sometimes desirable to modify fiber surfaces for particular end-uses. Most fiber friction modifications are accomplished by coating the fibers with lubricants or finishes. In most cases, these are temporary treatments that are removed in final processing steps before sale of the finished good. In some cases, a more permanent treatment is desired, and chemical reactions are performed to attach different species to the fiber surface, e.g. siliconized slick finishes or rubber adhesion promoters. Polyester s lack of chemical bonding sites can be modified by surface treatments that generate free radicals, such as with corrosive chemicals (e.g. acrylic acid) or by ionic bombardment with plasma treatments. The broken molecular bonds produce more polar sites, thus providing increased surface wettability and reactivity. 

Marshall, D.B. (1984). An indentation method for measuring matrix-fiber frictional stresses in ceramic composites. J. Am. Ceram. Soc. 67. C259-260. 

Commonly used textile lubricants to reduce fiber/metal and fiber/fiber friction. 

Special agent to increase the fiber/fiber friction in spinning, compatible with most spinning lubricants improves the tear strength of fabrics when used in finishing anti-slipping agent. 

A number of instrumental methods have been reported for evaluating variables associated with hair body [189-193], These methods measure changes in fiber friction, stiffness, curvature, diameter, weight, cohesion, and length. Treatments that increase the hair s curvature or diameter, increase the friction forces between fibers, or make the hair stiffer will increase body. Those that increase the cohesion between fibers or weigh them down will decrease hair body. 

Fabric softness is the result of the skin-fabric interaction and of the fabric mechanical properties. Fabrics are made of yarns, yarns being assemblies of twisted fibers. Fabric mechanical properties depend on the fabric geometry, on the yarn-yarn friction, and on the yarn mechanical properties. The mechanical properties of the yarn are determined by the fiber rigidity, by the fiber-fiber friction, and by the yarn geometry [26],... 

According to Chalmers [1], the softener forms a film over the entire surface of the fabric, with the fatty chains pointing away from the surface. There is some evidence for the correlation between the soft touch and the reduction of friction, friction between fabric and skin and between the fibers themselves [20], For instance, Roder and colleagues report an excellent correlation between softening efficacy and the interfiber friction coefficient. The latter was assessed by fixing a piece of treated textile to a metal block and measuring the force applied to move the metal along a fixed piece of the same textile [31]. Once the fiber-fiber friction coefficient decreases, the fibers move more independently of one another [3,27], The overall result is a 20% decrease of fiber abrasion [13] and fabrics are perceived as more flexible [3], The friction coefficient, however, increases when the relative humidity rises above 90% [20],... 

In this study, hair effects were measured by following changes in hair fiber friction. In general, the effect of chlorine was to increase the coefficient of fiber friction and to decrease the differential friction effect in hair. Changes in hair friction were observed even at parts-per-million levels of chlorine. Effects increased with the number of treatments and with decreasing pH from 8 to 2. 

ESCA [22] or infrared spectroscopy may be used. Physical methods such as fiber friction [21], light scattering [20], or examination of interfiber spac-ings [13], on the other hand, are less soil-specific than chemical methods and offer the ability to look at a variety of soil types, but sometimes these methods are less distinguishing in so doing. 

Certain laboratory tests (tress combing, fiber friction, fight scattering, sebum removing ability, etc.) can be more sensitive than consumer s evaluations (see the section in this chapter entitled Methods to Evaluate Clean Hair ). However, the most severe constraint with laboratory testing is that laboratory measurements are often only a portion of the related consumer assessment. For example, fiber friction is only a small part of how the hair feels to a consumer or how easily her hair combs, and hair combing is only a portion of hair conditioning. 

Factors That Influence Hair Fiber Friction... 

Table 8-20. Effect of bleaching on hair fiber friction [123] (high load).

Permanent waving also increases hair fiber friction [122], and its influence on hair properties is discussed in the last section of this chapter. 

For additional discussion of creme rinses and the effects of reduced fiber friction on hair properties, see the last section of this chapter. 

The results of this study indicate that curvature has the most impact on combing. The curvature effect is small when the hair is relatively straight, but it increases with increasing curliness. Fiber friction and stiffness also contribute to combing behavior, and the effect of these variables becomes more important as curvature decreases. These effects are most important... 

High-cleaning shampoos, when used on hair containing sebaceous sou, remove the surface oils and thereby reduce the cohesive bonding between fibers. These products thus provide for an improvement in style retention for dry look hairstyles. Certain conditioning shampoos provide a decrease in fiber friction and an increase in cohesive bonding and thereby provide for a limp look and a decrease in style retention for most styles. 

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