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Acrylic Thesis

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Introduction

Acrylics are a member of polymers that has been used for more that a century in many appliances such as for out door advertising, souvenirs, glazing and lots of other application that discussed in the later chapter in this article. Initially, acrylic acid was prepared in the laboratory over 100 years ago by the oxidation of acrolein or acrylic aldehyde, which obtained by dehydrating glycerine. However further research and development of this polymer was not started until 1900. In 1927 Rohm and Hass A.G. introduced 'Acryloid' and 'Plexigum' which was polymethyl acrylate. Soon, by the year 1932, an economic process of manufacturing methyl methacrylate was developed in the research laboratories of Imperial Chemical Industries and the process has been used worldwide till now (5). Methyl methacrylate was initially used for the production of cast sheet by bulk polymerisation followed by the development of granular polymerization technique to produce powder form for the use of dental prostheses. 3. Processing Method As mentioned above that the synthesis of methyl methacrylate was developed by the Imperial Chemical Industries limited, by chemical process known as the acetone-cyanohydrins process. Initially, Acetone is reacted with Hydrogen Cyanide to produce Acetone Cyanohydrin, this end product is further treated with sulphuric acid and methyl alcohol to yield methyl methacrylate monomer. ...read more.

Middle

by the formula: T = 10 + 3.15X Where T = time in minutes X = thickness in mm By considering all of these factors, this method will produces an isotropic acrylic sheet that is uniform properties in all direction without any grain present. Furthermore, it has a very low internal strain which leads to good dimensional stability. 5.2 Shaping The cast acrylic sheet is also can be formed into different shape. A practical guide can be used as indicator when a sheet is ready to be shaped that the sheet will spring back immediately when folded, and no sign of stiffness. There are two common method used for shaping an acrylic sheet, "free blowing" and "snap back" methods. 5.2.1 Free blowing The method is practically applying pressure to the heated acrylics sheet which secure by the clamping frame or mold of the desired shape. Normally used for aircraft glazing production. Flat bottomed vessels can also be obtained by blowing the sheet against a retaining plate. Blowing produce a thinning of the material in the area of greatest movement and this may result in reduction of strength of the article. Therefore care must be taken to prevent loss in strength of the article below acceptable limit. ...read more.

Conclusion

Because of its chemical resistance and non-toxicity it is used in food handling equipment and food display trays. Baths and wash hand basins are two of the many applications it finds in the sanitary ware field.(4) The injection molding of automotive light lenses from poly methyl meth. acrylate is almost universal because of its resistance to weathering and petrol and its low cost. Other automotive applications include insignia and indicator panels. Included in other applications are drawing instruments, tap handles, magnifying lenses, tumblers. For many years PMMA was limited to small moldings but with modern screw preplasticising machines and new techniques moldings used for roof lighting up to 1.6 m in diameter and weighing many kilograms are being produced.(4) The main application for extrusion until recently was light fittings but with improved extruder and die design the extrusion of sheet has become a major industry. Extruded sheet is improving all the time and is now being made to a quality approaching that of the more expensive cast sheet.(4) Conclusion This essay has been providing explanation of Acrylics, including the properties of cast sheet and granule polymerisation of acrylics, including their fabrication and processing. It has also mention about fabrication and processing of Cast Sheet Acrylic including forming and shaping by free blowing and snap back technique, and brief explanation on injection moulding granular polymers and compounds including type of injection moulding machine and machine temperature control. ...read more.

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