Transparent sheets

In the eady 1920s, experimentation with urea—formaldehyde resins [9011-05-6] in Germany (4) and Austria (5,6) led to the discovery that these resins might be cast into beautiful clear transparent sheets, and it was proposed that this new synthetic material might serve as an organic glass (5,6). In fact, an experimental product called PoUopas was introduced, but lack of sufficient water resistance prevented commercialization. Melamine—formaldehyde resin [9003-08-1] does have better water resistance but the market for synthetic glass was taken over by new thermoplastic materials such as polystyrene and poly(methyl methacrylate) (see Methacrylic polya rs Styrene plastics). 

Perspex, lucite. Transparent sheet and mouldings. Aircraft windows, laminated windscreens. 

Tough transparent sheet may be produced by blending standard polystyrene with block copolymer in an extruder in the ratios 80 20 to 20 80, depending on the application of the products subsequently thermoformed from the sheet. For example, sheet for thermoforming an egg tray will not require the same level of impact strength as that required for jam jars. 

FIGURE 14.40 The aluminosilicate mica cleaves into thin transparent sheets with high melting points. These properties allow it to be used for windows in furnaces. 

Diffraction grating The most common gratings are made of reflecting or transparent sheets marked with fine parallel and equally spaced grooves or rulings. The grating separates polychromatic electromagnetic waves into their components. Similar results can be produced with a prism, but the mechanism is quite different. Fraunhofer used very fine parallel wires in his experiments. 

Atkinson KR, Hawkins SC, Huynh C, Skourtis C, Dai J, Zhang M, et al. Multifunctional carbon nanotube yarns and transparent sheets Fabrication, properties, and applications. PhysicaB Condensed Matter. 2007 May 15 394(2) 339-43. 

Uses, The sole commercial use of MMA is polymers in various forms— case sheets, latices, and molding and extrusion polymers. MMA homopolymers (polymers that use only one monomer, as opposed to copolymers or terpolymers that use two or three) are best known for their use in the form of clear, transparent sheets with trade names like Plexiglas and Lucite, Applications include advertising signs, aircraft windows, desktops, lighting fixtures, building panels, and plumbing and bathroom fixtures. 

A distinction can be made between a positive and a negative resist, according to the action of light. In a positive working resist the monomer is deposited on the copper surface in the form of a viscous liquid. It is then irradiated through a mask (this is simply a drawing of the required pattern on a transparent sheet) and polymerization takes place only at the exposed places. The unirradiated liquid monomer is then washed away in a suitable solvent, and the exposed copper can be dissolved in an etching bath. Finally the protective polymer layer is removed by chemical or mechanical means, and the printed circuit is ready. 

Other changes are due to the presence of mites and of the larvae of insects, especially those of the yellow mead-worm (Tenebrio molitor) and the Mediterranean flour-moth (Ephestia Kuhniella). Larvae of insects are detectable by the naked eye. Mites may eaisily be observed by pressing a spoonful of flour on a sheet of paper with a transparent sheet of glass any mites present soon begin to move and render the surface of the flour in contact with the glass streaked with numerous irregular furrows. 

Later, the uses for transparent sheet included rules and set-squares for geometrical drawing, while pearlescent materials were highly effective for show purposes—as in drum kits for dance bands, accordions, and other musical instruments. Some pearl finishes were produced much as veneers, for embellishing small items like the handles of pen-knives. 

The cellulose nitrate plastics were adaptable, easy to work, and quite durable, but had the disadvantages of being plasticized with camphor and flammability (they burnt, in fact, quite violently). At one time the smell of camphor was thought pleasant (even therapeutic) but instances have been cited of harm to children attributed to inhaling this vapour. So, while the acetates were not quite so attractive in terms of ease of fabrication it was inevitable eventually that the so-called safety plastic would supersede its forerunner. Among other uses it was stitched into motor car tonneau covers as flexible glazing, and thicker transparent sheet was cut and formed into cockpit canopies for aircraft [though by that time the material preferred for this purpose was poly(methyl methacrylate)]. Later on, in their turn, sheets made from cellulose acetate butyrate and propionate took over some of the uses of earlier commercial materials. 

Methyl Poly(methyl Transparent sheets and mouldings ... 

Transparencies are still used for presentations made with overhead projectors, even with the explosion of programs like PowerPoint (from Microsoft) and peripherals like LCD computer displays, both of which let you show a whole roomful of people exactly what s on your computer screen. Actually, though, PowerPoint still has an option to print slides, and you can use any program you want to print anything you want to a transparent sheet of plastic or vinyl for use with an overhead projector. The problem is, these papers are exceedingly difficult for printers to work with. That s why special transparencies were developed for use with laser and bubble-jet printers. 

The Transparency Commission issues so-called transparency sheets which are in fact brochures in which a therapy is discussed for certcdn diseases and specific pharmacotherapeutic classes (e.g., medicines for the s5anptomatic treatment of age-related degeneration of the cognitive and affective functions, arteriopathy of the lower limbs, oesophagitis, hjrpnotics). Until now some 30 of these sheets have been published. Medicines with similar indications are compared and their pros cmd cons are discussed. Therefore, before an applicant receives notice on whether an MA has been granted, advice from two other sources is taken into consideration before the Minister makes the decision on whether to grant the MA. 

The Information and Publication Department monitors and controls advertising to doctors and the general public respectively, and would be responsible for official scientific publications (such as Folia Pharmaco-therapeutica), disseminating information on adverse effects, and drawing up and distributing transparency sheets. 

Use Acetate fiber, lacquers, protective-coating solution, photographic film, transparent sheeting, thermoplastic molding composition, cigarette filters, magnetic tapes, osmotic-cell membrane. 

Polypropylene MF membrane polyethersulfone UF membrane Acrylic transparent sheet... 

Transparent sheets and moldings more expensive than PS used for aeroplane windows e.g., Penpexi Plexiglass, Lucite, Diakon, Vedril. 

Methyl methacrylate CH, 1 CH5=C - 1 c=o 1 OCH3 Poly(methyl methacrylate) (PMMA) CH, —f-CH,—C— C=0 1 OCH3, Transparent sheets and moldings more expensive than PS known as organic gloss, used for aeroplane windows e.g.. Perspex, Plexiglass, Lucite, Diakon, Vedril. 

Brittle, yellowish, transparent sheets Or crushed pieces or powder, d 1.035-1.140. mp 115-120". Sapon no. 185-210 iodine no. 10-18. Solubility in alcohol 85 -95% w/w (very slowly sol) in ether 13-15% in benzene 10-20% in petr ether 2-6%. Sparingly sol in oil of turpentine. Inso] in water sol in aq solns of ethanolamines, of alkalies or borax with slightly purple color-... 

One of the oldest membrane materials used for dialysis is porous cellophane, a thin, transparent sheet made of regenerated cellulose. Typical values of parameters for commercial cellophane membranes are as follows thickness = 80 p.m, porosity = 0.45, tortuosity = 5.0, and pore diameter = 40 A (Seader and Henley, 2006). 

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