Silk fiber types

In a previous section, data and plots were given showing the rapid rise in consumption and production of manufactured fibers at the expense of natural fibers. The principal reason for this has been the wide range of manufactured fiber variants that can be produced from a single fiber-forming polymer. The wide range of polymers available, each with its particular properties, adds yet another dimension. This is not to say that there is only one type of cotton, wool, silk, or asbestos fiber there are many varieties of natural fibers, but their supply is limited by natural factors such as climate and genetics. The relative availabilities of manufactured fiber types can be altered by controlled chemical-process... 

To gain a better understanding of the effect of protein fiber type, dye, and mordant on sunlight and burial weathering processes, we dyed wool and silk with three phenolic dyes (found as major components in natural dye mixtures extracted from various plant sources) and post-mordanted samples of the dyed fabrics with five representative metal salts. We then exposed the unmordanted and the dyed-mordanted samples to simulated sunlight or soil burial and measured the differences in the color and tensile properties that resulted from these treatments. 

The degree of shade and depth of shade change in the buried dyed wool and silk samples were quite dependent on the dye applied and the fiber type to which it was applied. The unmordanted-dyed wool and silk samples tended to undergo large changes in shade and deepening of... 

As a form of direct fabric evidence, the physical shapes of textile fabric pseudomorphs have been studied to identify fiber type and yam and fabric construction. Pseudomorphs of paired filaments in mineralized fabric formations found on Shang-period bronze weapons were determined to be replaced silk (I, 2) S-and Z-twisted silk staple yarn pseudomorphs were identified as well as fabric constructions, including float yams and a ribbed weave. 

Let s start with creep, which is the easiest to understand. In a creep experiment you simply subject a sample to a constant (non-destructive) load or stress and watch it deform (i.e., measure the strain) as a function of time (Figure 13-72). The first systematic studies of this type were conducted by the German physicist, Weber, in 1835, who noted that silk fibers exhibited an immediate deformation upon loading, behavior that we call elastic, followed by an extension that gradually increased with time. Similarly, upon removing- the load both an immediate and delayed contraction were observed. In many... 

The other major natural fiber type, silk, fits the evidence. It is the only natural filament, and as such requires no twisting to be translated into a yarn for weaving. Silk is exuded from two orifices on either side of the silkworm s head and forms single strands called brins. The two brins then come together as a have unit which is held in place by sericin (17). A silk filament is smooth and maintains a relatively straight trajectory with no crimp to its structure. 

Most silkworm cocoon and spider dragline silk fibers contain assembled antiparallel p-pleated-sheet crystalline structures [33-35]. Silks are considered semicrystalline materials with 30-50% crystallinity in spider silks, 62-65% in cocoon silk fibroin from the silkworm B. mori, and 50-63% in wild-type silkworm cocoons. In the -sheet erystals the polymer chain axis is parallel to the fiber axis. The extent to which these struetures form, as well as their orientation and size, directly impact the mechanical features of silk fibers. Furthermore, the polyalanine repeats or... 

Other types of spider webs include tangle webs and sheet webs sptm by different species. Many other insects spin silk fibers for cocoons, shelter, egg sacs, egg stalks, and tunnels. For example, tarantulas use silk to spin tunnel-shaped shelters, and spin fibers from their feet as support lines. Caddisfiy larvae spin underwater tubes and nets, and the aquatic midge spins underwater silk tubes. Honeybee larvae spin silk to inCTease the mechanical strength and thermal stability of the beehive. These silks are subject to inaeasing amounts of research, as reviewed in Reference 11. 

The ingredients for pretreatments can range from simple to complex, with particular formulations for particular dye types or fabrics, or combinations of these. This chapter is an overview of pretreatment as a process, rather than a specific chemical or physical analysis of a particular step in that process. References are included for those interested to further their own research. Specific ingredients tend to be confidential as commercially sensitive, but some recipes are publicly available for use as a starting point for experimentation (Bae, 2007, p. 46 Hawkyard, 2006 Provost et al., 2003). Many of the pretreatment formulations have been aimed at fashion fabrics, so they are biased toward fiber types such as cotton, silk, nylon, and wool. The principle and most common ingredients for pretreatments are thickeners, alkalis, and urea ... 

Analysis of the world fibers supply since 1970 has showed that all fiber types suffered from demand reduction (Fig. 4.2). The established fibers like polyester, polyamide, polypropylene, and acrylic were down in volumes. The usage of cotton, wool, and silk also decreased by 10.1% to 25.2 million tonnes, and man-made fibers... 

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