Colour pastel

Since acetal resins are degraded by ultra violet light, additives may be included to improve the resistance of the polymer. Carbon black is effective but as in the case of polyethylene it must be well dispersed in the polymer. The finer the particle size the better the ultra violet stability of the polymer but the poorer the heat stability. About 1.5% is generally recommended. For white compounds and those with pastel colours titanium dioxide is as good in polyacetals as most transparent ultraviolet absorbers, such as the benzophenone derivatives and other materials discussed in Chapter 7. Such ultraviolet absorbers may be used for compounds that are neither black, white nor pastel shade in colour. 

The key properties here are hardness and wear resistance, ability to. stand minor knocks and dents without cracking and resistance to various domestic chemicals. These vary with type of appliance, e.g. detergent solutions are important for washing machines, while a fridge will be required to withstand fruit juices, ketchup and polishes. Good colour and appearance in white and mainly pastel shades will be expected. Corrosion resistance is required, especially for washing machines, and domestic appliances frequently have to withstand humid conditions in kitchens. 

The hue or vividness of colour may be correlated with the intensities of the absorption bands. Thus, Al-Fe epidotes, with relatively low molar extinction coefficients typical of spin-forbidden transitions within Fe3+ ions ( 3.7.2), exhibit pastel shades. The Al-Mn-Fe epidotes, however, display vivid colours correlating with high e values and originating from spin-allowed transitions within Mn3+ ions located in the very distorted acentric octahedral M3 site (fig. 

Cations of the lanthanide elements also produce colours in some minerals through intra-electronic transitions within 4/orbitals (Adams, 1965 Bernstein, 1982). Absorption bands are usually sharp and weak, leading to pastel shades. Examples of such coloured minerals are monazite, bastnaesite, rhabdophane, xenotime, gadolinite, and certain apatites, calcites, scheelites and fluorites. As noted earlier, some rare earth-bearing minerals, notably fluorite and monazite, also display the alexandrite effect (Berstein, 1982 Schmetzer et al., 1980). 

They are black solids with the PbCH (X = Cl) EuBr2 (X = Br) and Euh (X = I) structures. As with plutonium, only fluorides occur in the higher (>3) oxidation states. The trihalides are important they have the usual pastel colours, pink in the case of the fluoride and chloride, white-pale yellow (bromide), and pale yellow (iodide). 

Opaque glazes contain opacifiers either in frit (zircon, fluorides) or as a secondary component (Sn02). They are used wherever the body colour is to be covered or to attain pastel colour shades, in particular in building ceramics. Lead-free glazes are likewise given preference in industrial production. 

Figure 2.4.8 On site PASTEL UV measurements - Lake Stropu (See Plate 2 for colour representation)...

Figure 4.4.3 Nitrate concentration estimated by Pastel UV in the Hardt catchment (Roig et al 2007) (See Plate 4 for colour representation)...

Alcoholic fine fragrance. Contains 90% denatured, cosmetic-grade ethanol. Possibly lightly coloured (maybe a pastel shade). 

Appearance is only a guide to the type of plastic present because various fillers and colouring materials can change the appearance of a polymer considerably. However, Bakelite (phenol-formaldehyde) is always brown, black or red, while urea- and melamine-formaldehydes may have pastel shades. Polyethylene and polypropylene always appear slightly cloudy as thin films, while most other colourless plastics, particularly polyesters and polycarbonate, are crystal clear. 

Up to 10% of pigment by weight of cement may be added depending on the depth of colour required. Used with white Portland cement it is possible to produce pastel shades. 

Coloured pencils, pastels, charcoal and pens and pencils arc much gentler and generally will not cockle paper, though ihc> will need a good fixative (a cheap hair spray makes an ine.xpensh c alternative to c.vpensivc... 

For the interior of buildings, the paint has a special effect on illumination white and pastel colours increase the availability of natural and artificial light and influence mood and feelings. 

The spatial structures recorded from sealed tubes (10 mm diameter) were obtained in the Belousov Zhabotinskii reaction medium under similar conditions with initial concentrations potassium bromate 0.09M, sulphuric acid 0.4M, malonic acid 0.3M and cerous nitrate 1.2mM, Sufficient ferroin dye was included for a visual colour contrast of pastel blue waves in pale orange background to be enhanced by black and white photography (1, 2). 

UF plastics find widespread use because of their low cost and the possibility of pigmenting in a wide colour range, including pastel shades, not possible with PF materials. They have poorer water and heat resistance than PFs, only... 

Colourless white or pastel coloured mouldings can be produced from this resin using bleached wood pulp as a filler. Melamine-formaldehyde mouldings are more resistant to water than urea-formaldehyde resins and are not attacked by weak alkalies and they have a high heat resistance. 

Finally, consumers are demanding products that reflect their individuality and new styles in terms of design and colour are emerging much more quickly. In response to these trends plastics producers such as Dow and GE Plastics, have introduced lines of special effect resins. These can be used to create coloured moulded parts at a lower cost with special effects such as metallic, glitter, fluorescent, marble and pastel. 

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