Akruit — Acrylic Sheet Properties and Use | akruit.com
Seven standard figures for PMMA sheet, each with its unit and the condition under which it applies.
PMMA density is 1.18 to 1.20 g/cm3, roughly half that of glass. A large acrylic pane therefore weighs about half a glass pane of the same dimensions, which is the main reason acrylic replaces glass in overhead glazing and large display windows.
Light transmission reaches up to 92% of visible light at 3 mm thickness, and each surface reflects about 4%. Two surfaces at 4% each account for roughly 8% loss, which is most of the gap between 100% and the quoted 92%.
The glass transition temperature of atactic PMMA is 105 °C, while commercial grades range from 85 to 165 °C. Below this point the sheet is a rigid glassy solid; above it, the modulus drops sharply and the sheet can be thermo-formed.
On narrow screens, swipe or scroll the plate sideways.
PMMA ignites at 460 °C and burns to carbon dioxide, water and carbon monoxide. The absence of halogenated products simplifies fire classification for interior glazing and lighting diffusers.
The refractive index is 1.4905 at 589 nm, the sodium D-line. Optical designers use this single reference wavelength when calculating lens curvature and light-guide geometry.
The coefficient of thermal expansion is (5-10) × 10^-5 per °C, several times that of glass, so large acrylic panels need slotted fixings that allow the sheet to move as temperature changes.
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