Granular Breaks

Cellulosic and acrylic fibres, which are spun from solution, show granular breaks, which are similar to lower-magnification views of the structure of a fibre-reinforced composite, Fig. 5a,b. The reasons are similar. The fibres coagulate from solution with 

Granular fractures, (a) Cellulose fibre, (b) Acrylic fibre, (c) Human hair. For further explanation,. see Fig. I. 

In addition to solution-spun textile fibres, granular breaks are also found in some carbon fibres, which reflect their acrylic fibre origin, and in alumina fibres. Granular breaks are also shown in the natural fibres, wool and hair, in cotton at zero moisture content, and in resin-treated, cross-linked cotton at intermediate humidities. 

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On the C/H model, the limiting factor is the break extension of the matrix, which is less than that of the fibrils. Once the matrix has failed, the fibrils will come under higher tensions and will rupture to give a granular break. Cells may also break semi-independently, reflecting the composite of cells bonded by the CMC. 

Figures 12.10(a) and (b) show product in sheet form which is subsequently broken down to size. Pellets of large size also may be made for subsequent crushing. For instance, pellets 5cmdia by 1 cm thick are made for the pharmaceutical trade for breaking up to serve as coarse granular feed to tabletting.

The P break occurs at high input pressures for both liq and granular expls... 

The conversion so predicted tended to be somewhat lower than practical experience suggests, as illustrated in Figure 6. Since the predictions are based on theory and data for smooth, round wires, whilst industrial gauzes always present a very granular surface which is likely to break-up the boundary layer and to present a much larger effective surface area, the present agreement between prediction and experience must be considered to be satisfactory. 

Type 5 takes place when transverse discontinuities are present between structural units of the fiber and are sufficient to stop direct crack propagation. Breaks then occur with a granular surface roughly perpendicular to the fiber axis, as shown in our example of wool-fiber tensile failure (Figure 2). Once again, split-level transverse breaks are possible (5). 

Granular particles can be prepared in several ways. The toxicant may be added so as to impregnate the granule and thus be completely released only when the granule breaks up. It may be surface-coated on the granule using a volatile solvent, which evaporates from the formulation. The inert diluents can be clays or organic materials such as corncobs, pecan shells, tobacco stems, and walnut shells. 

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