Evaluation and testing methods

Fabric hand is defined as the estimated quality of a fabric, evaluated as reaction of the sense of touch, which is integrated in our brain to a total value. Important components of the sensory perception are the smoothness, compressibility and elasticity of the textile sample. As the hand of fabrics is primarily a subjective feeling - similar to the impression of colour - there have been many efforts to find methods for objective evaluation of the fabric hand. While instrumental colour measurement is very common in textile quality control, the automated measurement of fabric hand is still a topic of discussion and subjective manual hand evaluation is still the most important method. Simple methods to measure some aspects of fabric hand were described by Dawes and Owen. Many factors such as the colour of the textile, the hght and the surroundings, influence the manual evaluation of fabric hand. The American Association of Textile Chemists and Colorists has published guidelines for subjective hand evaluation.  

In some textile production laboratories single reference standards or a simple set of hand standards with different hand values is used. This set of standards is produced from the same fabric as the one being evaluated by applying the same softener at incremental concentrations. If the softener is used in combination with other finishes, the concentration of the other fmishes must be held constant. Relatively simple methods to evaluate only the bending properties of fabric (flex rigidity) are the cantilever method and a similar device called Softometer, which are described in Chapter 4 on hand building. 

The most comprehensive but most expensive method of objective hand evaluation was developed by Kawabata and co-workers and is called KES-F (Kawabata Evaluation System-Fabrics). It consists of several different measuring instruments, for example for tensile and shear properties (KES-Fl), bending properties (KES-F2), compressibility (KES-F3), surface (KES-F4) and thermal (KES-F7) properties. The measured parameters and the area weight are normalised and correlated to the subjective handle scores. From this correlation, for every hand evaluation a transformation equation is developed, resulting in a primary 

FAST (Fabric Assurance by Simple Testing) is another well known system. It was developed for quality assessment in the wool garment industry. FAST is less expensive and much quicker than the KES-F because it measures only some aspects of the fabric hand such as compression, bending, extension and dimensional stability at a few given points in a simplified form. The first three parameters correlate fairly well with the perceived softness but no quantitative hand values are calculated. For the evaluation of yam softness, there are several other devices in use, for example the p-Meter (Zweigle), a frictional balance (Reibwertwaage from Schlafhorst) and the F-meter. 

As can be seen, there are numerous instruments available to make objective, but incomplete, measurements of those physical properties that determine fabric hand. It is fair to say, however, that the best of these very expensive tools is, in general, not any better for making real time production decisions than an experienced finisher who knows what his or her customer expects. 

---

Biake linings and clutch facings consist of friction materials. Friction materials technology encompasses friction material types, their appHcations, friction and wear characteristics, raw materials, manufacturing methods, and evaluation and test methods. 

Chemical Anaylsis Modern Materials Evaluation and Testing Methods... 

---