Lateral sheeting

A few years later, Sheets suggested that co-oxidation of the biimidazole derived from 2-chloro-3, 4 -dimethoxybenzoin and o-chlorobenzaldehyde and 2-(o-chlorophenyl)-4,5-diphenylimidazole would give a still less expensive photo-oxidant (Scheme 4.13) with less visible sensitivity, thus making for better photofixing. 

Doring (39) has shown that infinite dilution relative volatilities can be evaluated through GLC. He prepared a special column for each solvent under consideration, a tedious project. A year later Sheets and Marchello (38) showed that separation factors increase with increased amounts of injected solvent. Later Tassios (35) found out the same to... 

Choker bar (restrictor bar) n. A bendable metal bar incorporated in a sheet-extrusion die for controlling flow distribution and lateral sheet thickness, and for reducing stagnation in the melt. The shape of a flow passage between the choker bar and the lower die body is altered by turning bolts coimected to the bar. 

The CWS first planned a civilian gas mask in 1937. By 1940 the service had decided that the design of the Zapon-type mask, as it was called, was not satisfactory, and had replaced it by another of rubberized fabric. At the request of the Office of Civilian Defense, the service redesigned this gas mask with its snout-type canister in five sizes for civilian use and obtained permission to produce it with laminated and, later, sheet rubber... 

The earliest SFA experiments consisted of bringing the two mica sheets into contact m a controlled atmosphere (figure Bl.20.61 or (confined) liquid medium [14, 27, 73, 74 and 75]. Later, a variety of surfactant layers [76, 77], polymer surfaces [5, 9, fO, L3, 78], poly electrolytes [79], novel materials [ ] or... 

The uptake, in column 10, has been converted into a liquid volume at the outset rather than at a later stage as in the original papers. Columns 1-8 are based on Table 3.2. In the original papers the values of p/p° corresponded to actual points on the experimental isotherm, but the work sheet is much simplified by the choice of standard intervals of pjp° (or of r " cf. p. 135). 

In 1954 the surface fluorination of polyethylene sheets by using a soHd CO2 cooled heat sink was patented (44). Later patents covered the fluorination of PVC (45) and polyethylene bottles (46). Studies of surface fluorination of polymer films have been reported (47). The fluorination of polyethylene powder was described (48) as a fiery intense reaction, which was finally controlled by dilution with an inert gas at reduced pressures. Direct fluorination of polymers was achieved in 1970 (8,49). More recently, surface fluorinations of poly(vinyl fluoride), polycarbonates, polystyrene, and poly(methyl methacrylate), and the surface fluorination of containers have been described (50,51). Partially fluorinated poly(ethylene terephthalate) and polyamides such as nylon have excellent soil release properties as well as high wettabiUty (52,53). The most advanced direct fluorination technology in the area of single-compound synthesis and synthesis of high performance fluids is currently practiced by 3M Co. of St. Paul, Minnesota, and by Exfluor Research Corp. of Austin, Texas. 

The crystal stmcture of PPT is pseudo-orthorhombic (essentially monoclinic) with a = 0.785/nm b = 0.515/nm c (fiber axis) = 1.28/nm and d = 90°. The molecules are arranged in parallel hydrogen-bonded sheets. There are two chains in a unit cell and the theoretical crystal density is 1.48 g/cm. The observed fiber density is 1.45 g/cm. An interesting property of the dry jet-wet spun fibers is the lateral crystalline order. Based on electron microscopy studies of peeled sections of Kevlar-49, the supramolecular stmcture consists of radially oriented crystaUites. The fiber contains a pleated stmcture along the fiber axis, with a periodicity of 500—600 nm. 

Composites. The history of phenoHc resin composites goes back to the early development of phenoHc materials, when wood flour, minerals, and colorants were combined with phenoHc resins to produce mol ding compounds. In later appHcations, resin varnishes were developed for kraft paper and textile fabrics to make decorative and industrial laminates. Although phenoHcs have been well characterized in glass-reinforced composites, new developments continue in this area, such as new systems for Hquid-injection molding (LIM) and sheet-molding compounds (SMC). More compHcated composite systems are based on aramid and graphite fibers. 

Fig. 9. A de novo designed P sheet protein, betabellin, formed by the dimerization of two identical four-stranded -sheets and a disulfide linking the two sheets. This model is for betabeUins 9 and later progenies the earher betabeUins contained a two-armed cross-linker connecting the sheets (51).

Figure 7 shows the crystal stmctures of graphite, ordinary (cubic) diamond, and hexagonal diamond. The layers of carbon atoms He in flat sheets in graphite, but in diamond the sheets are more wrinkled and He closer together. Taken separately, the sheets are similar, but they may be stacked in various lateral positions and stiU have bonding between them. 

The reduction of pH within the film unit is effected by a polymeric acid layer, as in the Polacolor process. The onset of neutralization is controlled by a contiguous timing layer. In the original SX-70 film unit these layers were on the inner surface of the transparent polyester sheet (Fig. 12) in Time-Zero SX-70 and later Polaroid integral films these layers are on the inner surface of the opaque negative support, as shown in Figure 13. 

Fig. 13. Schematic cross section of Time-Zero SX-70 integral film. In this film the polymeric acid layer and the timing layer are located beneath the negative layers, rather than in the positive sheet. Time-Zero and all later Polaroid integral films have an antireflection layer coated on the outer surface of the clear...

Finally, mild steel can sometimes show an instability like that of polythene. If the steel is annealed, the stress/strain curve looks like that in Fig. 11.10. A stable neck, called a Luders Band, forms and propagates (as it did in polythene) without causing fracture because the strong work-hardening of the later part of the stress/strain curve prevents this. Luders Bands are a problem when sheet steel is pressed because they give lower precision and disfigure the pressing. 

---