Weaving Preparation

During winding, yarns are wound from the feed onto a bobbin, which is usually a conical or cylindrical tube made of cardboard, plastic, or (seldom) metal. The reasons for winding are 

A large variety of bobbin sizes are available (DIN ISO 5239). Cross-wound bobbins that may be produced with random winding or precision winding are the most commonly used. 

Ply-yarn is a collective expression for all two-dimensional textile threads produced by the twisting of at ieast two yarns with S- or Z- twist (Fig. 4.4(a)). The feed yarns are twisted into a piy-yarn, which produces one- or muitiple-step piy-yarns depending on the twisting pattern (Fig. 4.4(b)). The German vocabulary is defined in DIN 60900, part 1. 

The number of twists is measured reiative to a iength of 1 m. To identify a piy-yarn, its structure is described by a combination of numbers (DIN 60900). 

The twist direction is usually opposite to the previous twist direction. Twisting in the same direction resuits in very hard and stiff piy-yarns with low elongation values. Because of the warp in weaving, the mechanicai stresses on the yarns are large, so relatively high-tenacity and highiy twisted piy-yarns are used. 

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Modified starches may be acid-modified, oxidized, or heat-treated. Acid-modified (thin-boiling) starches are used mainly in textiles as warp sizes and fabric finishes. Here they increase yam strength and abrasion resistance and improve weaving efficiency. Tbin-boiHng starches also have selected appHcations in paper and laundry starch preparations. 

Polycrystalline yttria-stabilized zirconia (YSZ-8) disks were prepared using 8 mol % Y203-doped zirconia powder (TOSOH zirconia, TZ-8Y, TOSOH Corp.). The powder was pressed uniaxially into disks which were cold isostatically pressed at 40,000 psi and then sintered at 1450°C for 4 h. Pt paste (Engelhard 6926) was painted on both faces of the YSZ-8 disks. Pt wires (0.0025 cm diam) were connected to the YSZ by using Pt meshes (150 X 150 mesh, 0.005 cm wire diam, Unique Wire Weaving Co., Inc.). 

Thus are the basic elements for making fabric prepared. Countless methods and structures of interworking such elements into fabric—e.g., weaving—have been developed throughout history (8). Depending on the abundance or scarcity and the type of raw material, various fabrics were developed in each geographical area to meet the need for protection against weather over time, many elaborations of the basic fabric types have been developed. 

Although most of my adult home and work life had been spent speaking English, I was prepared to miss the sound of Spanish weaving in and out of my days like the warm aroma of a familiar bakery. I knew I d miss the pleasure of moving back and forth between two languages—a pleasure that broadens one s human flexibility. 

Including 4-bromophenol in the phenol-formaldehyde resol system impacts the cross-link density of the cured product. In a systematic study of this copolymer, a comparison was made among the polymers obtained using phenol only, a 9 1 mole ratio of phenol to 4-bromophenol and a 1 1 mole ratio of phenol to 4-bromophenol. Comparisons included measurement of interlaminar shear strength and cone calorimetry tests of composites prepared using these phenolic resins and S2-glass fiber plain weave. 

This concludes our initial survey of chemical-potential gradients and their influence on a material s responses. We now turn our backs on chemistry and consider some ideas of a strictly mechanical kind for a couple of chapters, in preparation for weaving the two trains of ideas together (see Figure 5.3). 

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