Metallic yams

By itself a subject of study, metallic yam used in the past comes in a number of varieties that reflect the level of technology and trade of the time. A majority of metallic threads has been made into yarn by cutting prepared metallic material into strips that were then wound around a core thread of silk or linen. The metallic materials used were either gold or silver leaf adhered to membrane, parchment, leather, or paper or plain soft metal. Membrane is adversely affected by water and... 

Of the 64 fragments in the Brantley collection, 61 were found to be woven of silk, 1 was woven of silk and wool, 1 was woven of silk and cotton, and 1 was woven of cotton. Fifty of the samples contained metallic yams all were flat metal strips wound around silk yams in a spiral fashion except one which was woven flat without the core. These metallic yams were used both for ground fabric and for brocading. 

Figure 5. Optical microphotographs showing metallic yams of specimen M-l (a), TB-9 (b), TB-12 (c), and S-4 (d).

Film Applications Metallized polyester and BOPP films are suitable for flexible packaging, lamination, metallic yam, decoration, etc.t ... 

In most commercial conductive yams such as Shieldex (Alagirusamy et al., 2013) or SilverPam , silver is coated or plated onto polyamide core yams. Therefore, even though the intrinsic conductivity of silver is higher than other metals, the silvers weights, which can be plated onto yams, are still limited and affect the overall conductivity of the yams. Copper and stainless steel are more often used in the form of 100% metallic yams (Post et al., 2000) or can be blended with other yams such as polyester. The metals weights are much higher than for the silver. 

Co-spun polymer-metal yams. These consist of a polymeric textile fiber and a metal filament part united by a yam spinning method. 

The mechanical properties of a conductive material play an important role when selection is performed for any particular textile application. Metallic filaments usually compromise good electroconductive characteristics with poorer mechanical properties. A very high stiffness and lower stretchability of metallic fibers not only makes the woven or knitting process difficult but also reduces their service life. On the other hand, polymeric fibers or yams exhibit good elongation and recovery properties. The combination of nonstretchable metallic fibers with stretchable polymeric yams creates a new class of metal-based electroconductive fibers, which is known as co-spun polymeric-metal yams (Fig. 28.3). 

An important milestone was a patent from 1936 describing a method of producing multi-filament metal yam (James et al., 1936). Another patent from 1936 describes heated textiles incorporating iron, nickel, chromium or stainless metal wires (Grisley, 1936). A further patent describes the use of nickel-chrome strips to electrically heat socks (Costanzo, 1936). 

Modem approaches to the production of electrically conducting threads include conductive substrates, metal wires, metallized yams and inherently conductive polymers. It is notable that some of the approaches hark back to the methods used in ancient times. For example, a patent from 2005 describes how an electrically conductive fibre can be wound around an elastic core to produce a yam that can be elongated considerably (Nusco et al., 2005). Cottet et al. (2003) also report the use of copper threads following a helical path. 

Figure 2.2 Three typical structures of hybrid polymer-metal yams (a) metal-core yams, (b) polymer-core yams, and (c) polymer-metal braided yams. (Polymer fibers are shown in red, while metallic fibers are shown in gray.)...

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