Sep 4 2001
Polymethylmethacrylate (PMMA) is often known as "acrylic". While this actually describes a large family of chemically related polymers, PMMA is a colorless, transparent, and amorphous thermoplastic that is hard and stiff but brittle and notch-sensitive.
It has excellent optical clarity, good abrasion and UV resistance, but poor resistance to solvent, low temperature, and fatigue. Although it is flammable, it has low smoke emission.
General purpose grades can be extruded and injection moulded. Monomer casting is also used to obtain much higher molecular weights - which are not melt processable due to their very high melt viscosity - with somewhat better properties. The most commonly encountered monomer cast items are sheets and novelty displays in which, for instance, insects or watch parts are embedded.
Thin films are generally made from impact modified grades, which integrate a small proportion of elastomer(s) in order to enhance their flexibility.
Polymer Type
Thermoplastic
Advantages
Excellent clarity and UV resistance. Good abrasion resistance, hardness and stiffness. Low water absorption. Low smoke emission. Good track and arc resistance.
Disadvantages
Poor solvent resistance. Low continuous use temperature of approx. 50 °C (120 °F). Poor fatigue resistance. Notch sensitive.
Applications
Applications include lenses, light covers, glazing (particularly in aircraft), light pipes, meter covers, bathroom fittings, outdoor signs, skylights, baths, toys. Acrylic film is laminated over ABS sheet to provide UV protection.
Other applications include sinks, signs, and displays. Cast sheet is also used for guards and so on.
Source : Abstracted from Plascams
For more information on Plascams please visit RAPRA Technology Ltd.