PMMA processing conditions

PMMA processing conditions

Generic Class

PMMA (Polymethyl methacrylate)

Typical Applications

Automotive (signal light devices, instrument panels, etc.), medical (blood cuvettes, etc.), industrial (video discs, lighting diffusers, display shelving, etc.), consumer (drinking tumblers, stationery accessories, etc.)

Injection Molding Processing Conditions

Drying

PMMA is hygroscopic and must be dried prior to molding. Drying at 90 C (194 F) for 2-4 hours is recommended.

Melt Temperature 

240 - 280 C (460 - 536 F) 

Mold Temperature

35 - 80 C (90 - 176 F) 

Injection Speed

Moderate

Chemical and Physical Properties

Pellets for injection molding are made either by bulk polymerization of methyl methacrylate followed by extrusion and pelletization or by polymerization in an extruder. 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 generally 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 very low birefringence which makes it ideally suited 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.


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