Fibres twisting

Figure 13.7 Schematic illustration of a twisted then coiled fibre in which the change in fibre twist induces a length change in the coil for (a) heterochiral and (b) homochiral structures. c is the bias angle of the coil.

Polymer fibres are produced by forcing molten polymer or polymer in solution through fine nozzles (spinnerettes). The fibres so formed are twisted into a yarn and woven into fabric. Finally, polymers may be expanded into foams by mixing in chemicals that release COj bubbles into the molten polymer or the curing resin, or by expanding a dissolved gas into bubbles by reducing the pressure. 

Tow A large bundle of fibres generally 10,000 or more, not twisted. 

Fig. 10 (a-f) Hierarchical self-assembly model for chiral rod-like units A curly tape (c ), a twisted ribbon (d ), a fibril (e ) and a fibre (f). Adapted from Aggeli et al. [20], Copyright 2001 National Academy of Sciences, USA... 

The twist of these aggregates determines the resulting structure. When ribbons stack into fibrils, and fibrils into fibres, packing considerations cause these twisted aggregates to bend and modify their twist with an elastic energy penalty8eiast- For fibrils, it can be shown that the afibrii per peptide in a fibril is ... 

The twisted fibre of polyester, rayon, nylon or steel, which imparts strength to the tyre carcase and belt. See Tyre Cord. 

The coiling together of textile staple fibres, yams or threads to give the structure the required degree of strength, extensibility, flex resistance, etc. Twist is designated as so many turns per inch and either right hand (Z) or left hand (S). See S-Twist and Z-Twist. 

Filament yams can exist in an almost twistless form, but this is not the case for staple fibre yams. The twisting of fibres together is still the most practical method of making short fibres into long continuous strands of yam suitable for weaving. See S-Twist and Z-Twist. 

ISO 15310 1999 Fibre-reinforced plastic composites - Determination of the in-plane shear modulus by the plate twist method... 

ISO 1889 1997 Reinforcement yarns - Determination of linear density ISO 1890 1997 Reinforcement yarns - Determination of twist ISO 2113 1996 Reinforcement fibres - Woven fabrics - Basis for a specification ISO 2113 1996/Cor 1 2003... 

Cotton. Cotton is furnished by the down surrounding the seeds of various species of Gossypium. This fibre, which is unicellular and closed at only one end, is always isolated, and appears under the microscope as a ribbon twisted at intervals on its own axis like a spiral (Fig. 68, Plate VI). The wall is comparatively thin and sometimes somewhat raised like a rim the lumen is wide—three or four times as wide as the walls. This lumen is mostly empty, but sometimes contains granulations representing the original protoplasm in a dried state. The cotton fibre, which consists solely of cellulose, is coated in the raw state with a very thin cuticle, which is readily seen in a dry microscopic preparation. When raw cotton is treated with ammoniacal cupric oxide solution, whilst the cellulose of the fibre first swells and then dissolves, the cuticle remains almost intact, so that the fibres assume characteristic microscopic forms. The section of the cotton fibre (see Fig. 69, Plate VI) is elliptical, curved or reniform, with a fissure-like lumen. 

When the sample is dehydrated the X-ray diffraction pattern obtained is of poorer quality (Fig. 4b) and is similar to that reported for lentinan (8). We suggest that the removal of water causes a twisting of the chains back toward the six-fold triple-stranded model. On annealing, the sample completes this transition (Fig. 4c) by exhibiting a pattern similar to Figure 3. The reflections observed in Figure 4c index on a hexagonal unit cell with dimensions a = b = 1.530 nm, c (fibre axis) = 1.76 nm and the measured densTty Ts 1.52 g/cm . 

Fligherwet pickup with hydrophilic fibres Fligher wet pickup with low twist and/or open end yarns... 

---