Polymethyl methacrylate (PMMA) has excellent chemical and weather resistance.
PMMA is hygroscopic and must be dried before molding. Drying at 90 C [194 F] for 2-4 hours is recommended.
240 C 280 C [460 F 536 F]
35 C 80 C [90 F 176 F]
Moderate
Bulk polymerization of methyl methacrylate followed by extrusion and pelletization, or polymerization in an extruder make pellets for injection molding. Formulations vary by molecular weight and physical properties such as flow rate, heat resistance, and toughness. Higher molecular weight grades are tougher than lower molecular weight grades. High flow formulations are preferred for molding.
Heat deflection temperature under load varies from 75 C [167 F] for high flow materials to 100 C [212 F] for low flow (high molecular weight) materials.
PMMA has excellent optical properties and weatherability. The white light transmittance is as high as 92%. Molded parts can have low birefringence, which makes PMMA suitable as a material for video discs.
PMMA exhibits room temperature creep. The initial tensile strength is high but under long-term, high-stress loading, it exhibits stress craze. Impact strength is good but it does show some notch sensitivity.