Colouring materials, synthetic

Peereboom [52], using various solvents, has separated numerous synthetic and naturally occurring fat-soluble colouring materials on silica gel G, alumina G and kieselguhr G. The results are given in Table 125. 

Food products, which undergo undesirable colour changes in the presence of enzymes and oxygen, are sterilised to achieve the inactivation of enzymes, and stored in an inert atmosphere or in the presence of antioxidants. In cases where it is impossible to prevent the degradation of carotenoids (e.g. during the storage of flour or the manufacture of pasta, losses of carotenoids can reach 30-60%), the material can be coloured using synthetic carotenoids. 

There is today much argument as to whether or not colouring materials should be added to foods to improve their appearance and attractiveness Colours (whether natural or synthetic) may be added to foods for any of the following reasons ... 

Today the principal outlets are knife handles, table-tennis balls and spectacle frames. The continued use in knife handles is due to the pleasant appearance and the ability of the material to after-shrink around the extension of the blade. Table-tennis balls continue to be made from celluloid since it has been difficult to match the bounce and handle of the celluloid ball, the type originally used, with balls fabricated from newer polymers. Even here celluloid is now meeting the challenge of synthetic polymers. Spectacle frames are still of interest because of the attractive colour. There are, however, restrictions to their use for this application in certain countries and cellulose acetate is often preferred. 

Phenolics. Phenol-formaldehyde (Bakelite) is one of the oldest synthetic materials available. It is a strong, hard, brittle material with good creep resistance and excellent electrical properties. Unfortunately the material is only available in dark colours and it is susceptible to attack by alkalis and oxidising agents. Typical applications are domestic electrical fittings, saucepan handles, fan blades, smoothing iron handles and pump parts. 

Do you think that daily life would have been easier and colourful without the discovery and varied applications of polymers The use of polymers in the manufacture of plastic buckets, cups and saucers, children s toys, packaging bags, synthetic clothing materials, automobile tyres, gears and seals, electrical Insulating materials and machine parts has completely revolutionised the daily life as well as the industrial scenario. Indeed, the polymers are the backbone of four major Industries viz. plastics, elastomers, fibres and paints and varnishes. 

A different system has been introduced by Index Instruments [2]. This modular analysis system (MAS) provides the analysis of up to four different parameters refractive index, density, colour and optical rotation. A wide range of viscosities can be handled. The analysis, wash and drying times can be selected by computer control so that crosscontamination can be reduced to undetectable levels. Samples are only in contact with inert materials such as glass, synthetic sapphire, PTFE and 316 stainless steel. 

Synthetic MIO is used in primers as well as in topcoat paints the natural MIO was too coarse for use in undercoats. Weathering tests with different paint binders indicated that the performance of the synthetic product was as good or better than, that of the natural product (Carter and Laundon, 1990). The aspect ratio of MIO produced by hydro-thermal synthesis can be altered by doping with Al, Mn or Si, thus enabling a more lustrous material with a reddish-brown colour to be produced this material is suitable for decorative as well as for purely protective purposes (Pfaflfand Reynders, 1999). 

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