Gramophone records

In addition to homopolymers of varying molecular and particle structure, copolymers are also available commercially in which vinyl chloride is the principal monomer. Comonomers used eommercially include vinyl acetate, vinylidene chloride, propylene, acrylonitrile, vinyl isobutyl ether, and maleic, fumaric and acrylic esters. Of these the first three only are of importance to the plastics industry. The main function of introducing comonomer is to reduce the regularity of the polymer structure and thus lower the interchain forces. The polymers may therefore be proeessed at much lower temperatures and are useful in the manufacture of gramophone records and flooring compositions. 

For some applications it is necessary that static charge should not accumulate on the product. This is important in such diverse applications as mine belting and gramophone records. The use of antistatic agents such as quaternary ammonium compounds has been of some limited value in solving this problem. 

Copolymers were also used in gramophone record formulations (Formula 6). No filler can be tolerated and stabilisers and lubricants are chosen that give records of minimum surface noise. Antistatic agents may also be incorporated into the compound. 

Vinyl chloride-vinyl acetate copolymers may be processed at lower temperatures than those used for the homopolymer. Their main applications were in gramophone records and flooring. Gramophone record compositions are unfilled... 

For many years vinyl chloride-vinyl acetate copolymers had two main uses, in flooring compositions and for long playing gramophone records. Whereas the former application remains strong, the use in gramophone records has dropped sharply, particularly since the widespread acceptance of polycarbonate-based compact discs. 

Variation in the details of the solvent processes will produce different grades of shellac. For example, when cold alcohol is used, lac wax which is associated with the resin remains insoluble and a shellac is obtained free from wax. Thermally processed shellacs were greatly favoured for gramophone records as they were free from residual solvent and also contained a small quantity of lac wax which proved a useful plasticiser. 

Until 1950 the principal application of shellac was in gramophone records. The resin acted as a binder for about three times its weight of mineral filter, e.g. slate... 

Aluminium is widely applied for decorative and protective requirements, while cadmium , zinc and titanium have been applied to ferrous materials chiefly for their protective value. The method finds particular application in the plating of high-tensile steels used in aviation and rocketry, car fittings and lamp reflectors, and gramophone record master discs, as well as in the preparation of specimens for electron microscopy and in rendering insulated surfaces electrically conducting, e.g. metallising of capacitors and resistors. 

In order to improve toughness many rubbers and other soft polymers may be used as additives to modify the compound. Some copolymers based on vinyl chloride are available of which the most important are the vinyl chloride-vinyl acetate materials used in gramophone records, flooring compositions and surface coatings. 

Rayner and Godsill, 1991] Rayner, P. J. W. and Godsill, S. J. (1991). The detection and correction of artefacts in archived gramophone recordings. In Proc. IEEE Workshop Appl. of Signal Processing to Audio and Acoustics, Mohonk Mountain... 

Spenser, 1990] Spenser, P. S. (1990). System Identification with Application to the Restoration of Archived Gramophone Recordings. PhD thesis, University of Cambridge. 

Spenser and Rayner, 1989] Spenser, P. S. and Rayner, P. J. W. (1989). Separation of stationary and time-varying systems and its application to the restoration of gramophone recordings. Proc. ISCAS89, Oregon, 1 299-295. 

Tracing distortion in gramophone recordings [Roys, 1978] the result of the playback stylus tracing a different path from the recording stylus. This can occur if the playback stylus has an incorrect tip radius. 

The product, formed via the fluid state is, in some cases, the end-product, but may also be subject to further shaping as an intermediate product. Examples of the first case are injection-moulded gear-wheels, compression-moulded gramophone-records, extruded and on-line blown bottles, etc. In the second case an extruded sheet is, for instance, subjected to a heat-forming process to produce a light-dome a gear wheel may be machined from a compression-moulded block, or an extruded tubular film is... 

Thermoplasts, thermosets and rubbers can be processed by compression moulding. For thermoplasts this technique is an exception the best known example is the manufacture of gramophone records from a copolymer of vinyl chloride and vinyl acetate (chosen to enable a very good flow into all details of the mould). 

Shellac was a substance excreted by insects. It was mixed with wood flour, moulded and dyed - usually black or brown. It was lifter Than bois duici and gave good detail in moulding. It was used to make picture flames (F. 13.1), dressing table sets, some jewellery and, notably, 78 tpm gramophone records. Examined under a microscope it is possible to see the wood content. Black shellac gives a black streak. 

Shellac is dark in colour, and is usually dyed black, red or brown. Its best known uses were as gramophone records. Another use was for American Union cases, which were small boxes used as folding picture frames (Fig. 13.1). They could be closed to preserve the silver nitrate coated glass photo des called Daguerreotypes, which deteriorate in the h t. Shellac was also used fin dressing table sets and for brooches. It is a britde material and can crack or chip. Shellac is compression moulded, and is still produced today. 

Water pipes and gutters, bottles, gramophone records, plasticized to make PVC leather doth, raincoats, flexible pto and hose. toys, sheathing on electrical cables, e.g., Benvic,. Darvic, Geon. Hostalit, Solvic, Vinollex, Weivic. 

Humus in the soil and some kinds of lignite (brown coal) are examples of organic ion-exchangers found in nature. After discovery that ion-exchange could be performed in aqueous solution on finely ground gramophone records, Adams... 

Now that the original designs for most everyday objects are stored in computers, it is no longer easy to find an example from everyday life to illustrate this idea. Before vinyl gramophone records disappeared from the market in the... 

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