Resistance to Compression Behavior of Alpaca and Wool

Abstract

This study compares the resistance to compression behavior of wool and alpaca fibers. It shows that alpaca fibers have a much lower resistance to compression than wool, and there is little correlation between the resistance to compression and the curvature for alpaca fibers. Yet for wool fibers, the correlation between resistance to compression and curvature is very strong and positive. The differences in fiber curvature and scale profiles of alpaca and wool, together with the test method for resistance to compression, may explain their different resistances to compression. Alpaca fibers are soft and are typically blended with Merino wool or other fibers for use in overcoats and high fashion knitwear. The development of the rare animal fiber industry has considerably increased interest in alpaca animals and alpaca fiber products. When touching alpaca and wool fibers, people often wonder why alpaca is so much softer than wool, even when the alpaca fibers are a few microns coarser than wool. Soft handle is a result of subjective evaluation [ 15], and involves a combination of fiber/fabric characteristics, such as surface roughness/smoothness, bending stiffness, compressibility, resilience, extensibility, fabric thickness, and so on.The fiber/fabric may be soft if it is smooth, easier to compress and suppler, and has a lower bending rigidity.The softness of loose wool depends heavily on its fiber diameter (FD) [ 19]. Crimp characteristics (crimp frequency and definition etc.) play a minor but significant role in softness through their influence on compressibility [ 17]. Many studies have reported the effect of crimp on quality of tops, yams, and fabrics, and on the ease of processing and spinnability [ 1, 2, 8 -11, 15, 20, 21 ]. The general agreement is that low crimp frequency is associated with longer hauteur in top, lower romaine in combing, better yarn evenness, and fewer ends-down. Low crimp wool can be spun into a finer count yam and produces a thinner, softer, smoother, leaner, and less pilling fabric. Because of the high correlation between crimp frequency and resistance to compression (RtC) [4,12,18], the softness of a knitted fabric is also related to the RtC value of raw wool. Madeley et al. reported that compressibility of knitted fabrics increases and bending rigidity decreases as loose fiber RtC decreases [10]. Fabric stiffness also decreases with decreasing loose fiber RtC and staple crimp. Fiber curvature may be used to describe the spacefilling properties of a mass of wool fibers [6]. There is a strong relationship between crimp frequency and curvature [23]. The inherent fiber curvature lies within the wool follicle [3], and staple crimp frequency is basically an expression of the curvature of the fibers within the staple [23]. Reductions in fiber curvature reduce fiber bending rigidity [111 and yam thickness [22] and increase the soft handle of fabrics.Since measuring resistance to compression (RtC) is an objective way to reflect fiber compressibility, and the latest fiber curvature (Cur) measureme...

Evaluating the Softness of Animal Fibers

“…However, the current RtC test method is strongly related to fiber crimp and curvature. It is not suitable for lowcurvature fibers such as alpaca, and is not a good softness indicator for fibers of different types with varying diameters [8]. For instance, a very fine fiber with high curvature usually has a much higher RtC value than a much coarser fiber with a low curvature, even though the fine fiber is much softer than the coarser one.…”

Compression and surface properties of Mongolian cashmere tops related to tactile characterization

“…Compressional softness has been discussed in the literature in relation to fiber diameter, FC and fiber length. 15,[17][18][19][20] As given in Table 1, the MFD for the three cashmere samples ranges from 15.33 to 16.23 mm.…”

“…For merino wool, Rc is related to the wool grade, 14 but Rc is not a softness indicator for alpaca fibers. 15 McGregor 7 considered 101 samples from commercial lots collected from different sources around the world. The tendency is for the MFD of cashmere to increase slightly with decreasing Rc.…”

Influence of Ultraviolet Irradiation and Protease on Scale Structure of Alpaca Wool Fibers

“…Investigators have been exploring the properties and modifi cation of alpaca wool fi bers for 30 years even sometimes mainly focusing on the development of an anti-shrinkage process for wool-based textiles [7][8][9][10][11][12][13][14]. Wool fi bers felt when agitated in water due to having a substantial differential frictional effect (DFE) in cuticle structure.…”