Acrylic thermoplastics, from Allplastics , are products of polymerization of acrylic estermonomers. The materials are available in cast sheet, continuous cast and extruded sheet, film and a number of compounds for injection molding and extrusion. Tubes and rods can also be cast or extruded from the monomer or polymer.
Cell-cast sheet is produced in a variety of sizes and thicknesses. The largest sheets available are 120x144 in. Thicknesses range from 0.030 to 4.25 in. Continuous cast material is supplied as flat sheet and in coils in lengths to 600 feet and widths to 9 feet. Maximum thickness is ½ in. Acrylic sheet cast in the continuous process (between stainless steel belts) is more uniform in thickness than cell-cast sheet. Cell-cast sheet, on the other hand, which is cast between glass plates, has superior optical properties and surface qualities. Also, cell-cast sheet is available in a greater variety of colors and compositions. Cast acrylic sheet is supplied in general-purpose grades and in ultraviolet absorbing mirrored and superthermoformable sheet grades.
All cast grades are strong, stable, weather resistant and thermoformable. Sheets are also available in transparent, translucent and opaque colours, and in a variety of surface textures.
Extruded sheet is produced by forcing Acrylic pellets through a conventional screw extruder. The Acrylic is pushed through a sheet die in a continuous process allowing for a variety of widths and lengths within practical or economical limits.
Sheet coating is available at a premium price to those who object to the scratching and marring of Acrylic sheet. A number of coating processes are available at this time. Coating imparts a "hard" film to the surface of the sheet, greatly increasing its marr resistance, cleanability, and chemical resistance, but sometimes reducing thermoforming capabilities.
When selling acrylics remember that transparency, gloss, and dimensional shape of acrylics are virtually unaffected by years of exposure to the elements, salt spry, or corrosive atmospheres. These materials withstand exposure to light from fluorescent lamps without darkening or deteriorating. They ultimately discolour, however when exposed to high-intensity UV light below 265 nm. Special formulations resist UV emission from light sources such as mercury-vapour and sodium-vapour lamps.
Colorants can be added to produce to full spectrum of transparent, translucent or opaque colours. Most colours can be formulated to give long-term outdoor durability. Acrylics are normally formulated to filter ultraviolet energy in 400 nm and lower band.
Mechanical properties of acrylics are high for relatively short-term loading. High stresses can be sustained safely for short periods; but for long service, tensile stresses must be limited to 1,500 psi to avoid crazing or surface cracking.
Acrylic plastics are among the most scratch resistant of all thermoplastics. Toughness of acrylic sheet, as measured by resistance to crack propagation, can be improved by inducing molecular orientation during forming. Jet aircraft cabin windows, for example, are made from oriented acrylic sheet.
Special ultraviolet-absorbing grades are used for document preservation in museums and for various photographic applications.
Specially formulated acrylic sheet is available for deeply formed components such as tub and shower units, which are subsequently backed with glass-fibre reinforced polyester.
Sheet extruded from the high-impact moulding grade is used for:
> Thermoformed Products
> Glass-fibre Polyester backed components such as Camper Tops, Furniture and Recreation Vehicle Bodies
Rod and tube are available in both extruded and cast grades, the selection of which should be determined by the quality level desired when compared to cost considerations.
Cast rod and tube is manufactured from raw monomer, which is cast or poured into moulds. Once cured, the material is ground to size and then highly polished and finished dimensions.
Casting in the more expensive of the two processes but yields a better quality product. Cat rod is available up to 8" in diameter; tube may be purchased up to 24" OD. Slab stock may also be manufactured in this manner, so that thick "sheet" not available by conventional means may be purchased from a number of independent custom manufacturers.
Extruded rod and tube is manufactured by a number of extruders who push Acrylic pellets through a highly polished extrusion die to produce a finished product. Die marks and other imperfections make extruded rod and tube somewhat less desirable. The process is less expensive, however, opening up many markets for distributors.