Mechanical Profilometry of Wool and Mohair Fibers

Abstract

In the scanning electron microscope, the surface of wool fibers is much rougher than that of mohair or other specialty fibers, mainly due to differences in the frequency and height of the cuticle scales. In order to assess and quantify these differences, which are essential for the perception of "roughness" and thus for fast fiber discrimination, mechan ical profilometry is used to assess coarse Merino wool and Texas mohair fibers. The data are analyzed by smoothing and Fourier analysis to separate cuticle-related effects of roughness from longer term fiber diameter changes attributed mainly to the characteristic circadian (daily) biological rhythm of the animal. The results show that subjectively observed differences in the roughness of the two fiber types are reflected in roughness and frequency parameters obtained from their mechanical profiles, enabling reliable discrim ination between wool and mohair.

Quantitative Fiber Mixture Analysis by Scanning Electron Microscopy

“…Though emphasis is placed on cuticle scale height as a tool for fiber discrimination, special reference is made to the importance of other fiber surface characteristics, enabling the experienced operator to rapidly identify fibers. The specific role of cuticle scale height for the selectivity of the method has been emphasized by Robson [ 19], and is consistent with the characteristic differences in surface roughness observed for, e.g., wool and mohair [33]. Furthermore, even harsh chemical processing has only a very limited influence on the selectivity of the CSH criterion for fiber identification [15,30].…”

Spatial Probing of the Properties of the Human Hair Surface Using Wilhelmy Force Profiles

“…This leads to conclude that the observed effects are not significantly influenced by diameter changes. However, it is important to note that hair diameter also shows systematic, cyclic changes along hair length and thus with time. , …”

“…The raw wetting force data of variable spacing were converted to equally 5 μm spaced data points through interpolation to yield the primary profile (Figure a). The results from mechanical surface profilometry of human and animal hair lead to expect cyclic phenomena for the daily as well as the monthly time scale, linked to biological rhythms. Against this background and in analogy to procedures established for the analysis of surface roughness a curve, referred to for these investigation as the secondary profile (Figure b), was generated by Gaussian core smoothing over number of data points equivalent to a 2 mm fiber length .…”

“…Motivated by results from the surface profilometry of human hair and animal fibers as well as through previous Wilhelmy investigations on wool fibers, we investigate here whether the wettability or Wilhelmy force curves along a hair yield just the overall contact angle and are fractal in nature beyond that or whether they comprise in fact detailed information about the fine structure of the hair surface, namely, with respect to space- and thus time-related phenomena.…”

Investigation of the structure changes and properties of stretched mohair fibre

“…The cuticle cells or scales surround the cortex, which avoid the damage from the external physical and chemical environment [1,2]. However, the scales of mohair fibres have lower scale frequency and are smoother than that of wool fibres, and they closely cling to the flat shaft with few overlapping [3]. With the age growth, mohair fibre becomes thicker and poorer quality.…”