Short answer: Acrylic has no sharp melting point; it softens gradually. Makers rate it for continuous use up to about 160 °F (71 °C) for extruded and 180 °F (82 °C) for cast sheet; it deflects under load at about 195 to 210 °F (ASTM D648 at 264 psi), reaches its Vicat softening point at about 220 °F (105 °C) extruded to 239 °F (115 °C) cast, is formed at roughly 290 to 380 °F, starts decomposing into monomer above about 570 °F (300 °C), and self-ignites at about 750 to 910 °F (ASTM D1929).
Why doesn't acrylic have a melting point?
Acrylic (PMMA) is an amorphous plastic: its long molecules are tangled randomly rather than lined up in crystals. Crystalline materials melt at a single temperature. Amorphous ones like acrylic soften gradually as they warm through a glass transition region (for acrylic, roughly 210 to 230 °F, about 100 to 110 °C) and keep getting softer as they get hotter. Before it ever becomes a runny liquid, acrylic starts to break down chemically.
What temperatures can acrylic handle?
Typical values from sheet makers' data sheets. They vary with grade, thickness, and load.
| Temperature | What happens | Source values |
|---|---|---|
| -40 °F (-40 °C) | Low end of service range. Stronger, but more brittle. | Acrylite cast: usable from -40 °F |
| 160 to 180 °F (71 to 82 °C) | Maximum continuous service temperature. | Acrylite FF 160 °F; Optix 175 °F; Acrylite cast 180 °F; Plexiglas G 180 to 200 °F; Röhm GS 80 °C, XT 70 °C |
| 190 to 200 °F (88 to 93 °C) | Short, intermittent exposure limit. | Acrylite FF 190 °F; Acrylite cast 200 °F |
| 195 to 210 °F (91 to 99 °C) | Heat deflection temperature: a loaded bar bends. Loaded or thin parts warp. | ASTM D648 at 264 psi: Acrylite FF 195 °F, Optix 200 °F, Plexiglas G 205 °F, Acrylite cast 210 °F |
| 220 to 239 °F (105 to 115 °C) | Vicat softening point: clearly soft. | Acrylite FF 220 °F, Acrylite cast 239 °F (ASTM D1525); Röhm XT 103 °C, GS 115 °C (ISO 306 B50) |
| About 290 to 380 °F (145 to 193 °C) | Forming range: rubbery; used for bending and thermoforming. | Acrylite FF about 300 °F; Plexiglas G 290 to 360 °F; Röhm GS 160 to 175 °C; Acrylite cast 340 to 380 °F |
| 350 to 410 °F (177 to 210 °C) | Surface bubbling with time or overheating. | Plexiglas G bubbles after 5 h at 350 °F, 15 min at 400 °F; strip-heated surfaces bubble above about 410 °F |
| Above about 570 °F (300 °C) | Thermal decomposition into methyl methacrylate monomer vapor. | Plexiglas G safety data sheet |
| About 750 to 910 °F (400 to 490 °C) | Self-ignition (no flame needed). | ASTM D1929: Optix 750 °F, Acrylite FF 850 °F, Plexiglas G 860 °F, Acrylite cast 910 °F |
Heat deflection temperature (HDT) measures when a loaded bar bends a set amount; Vicat measures when a needle presses a set depth into the surface. Both say "this is where it gets soft," measured differently. Strength drops well before either: Röhm lists cast PLEXIGLAS at about 80 MPa tensile strength at 73 °F but about 40 MPa at 158 °F (70 °C).
Can I put a hot dish on acrylic?
No. A pan straight off the stove or out of the oven is often 300 °F or more, well into acrylic's softening and forming range. It can leave a ring, a warp, or cracks. Use a trivet. Hot coffee mugs (around 140 to 180 °F) are usually fine on a tabletop cover, though a coaster is wise. Acrylic coasters themselves are fine for drinks.
Is acrylic safe near light bulbs?
LED fixtures run cool enough for acrylic diffusers and covers, which is why acrylic is so common in lighting. Acrylite specifically warns against exposing acrylic to high-wattage incandescent lamps unless the fixture is ventilated to dissipate the heat. Keep acrylic well away from halogen and incandescent bulbs, or use a fixture designed for the bulb.
Can acrylic go near a heater, stove, or fireplace?
Not close. Radiant heat from a space heater, wood stove, or fireplace can soften and warp acrylic at a surprising distance, and acrylic is combustible. Keep it well clear and follow the appliance's clearance rules. For a fireplace screen or stove guard, use tempered or ceramic glass made for the job. See is acrylic flammable.
Will acrylic warp in a hot car?
It can. Dashboards in direct sun can reach temperatures near acrylic's short-term limit, and thin, dark parts left there absorb the most heat. Inside the cabin, out of direct sun, most acrylic items are fine.
Can acrylic go in the dishwasher?
Hot dishwasher cycles and drying heat can warp or craze it. Hand washing is safer. Dishwashers and microwaving have their own pages.
How does heat change acrylic's size?
Long before it softens, acrylic expands with heat, about 0.00004 in./in./°F, roughly 3 times metals and 8 times glass (Acrylite). A panel in the sun can grow noticeably and bow if it's held too tightly. See acrylic thermal expansion. Formed acrylic also has elastic memory: Acrylite says parts heated above about 210 °F may revert toward their original flat shape.
When should you choose a different material?
For parts that must stay rigid above roughly 180 °F, polycarbonate holds its shape to higher temperatures; for real heat (stove guards, oven windows, fireplace screens), use glass or metal. Acrylic vs polycarbonate.
Heat as a tool
The same softening that makes acrylic unsuitable for hot surfaces is what lets us bend it into stands and holders, and what lets a laser cut it with a polished-looking edge. Order parts through the instant quote.
Questions
Can acrylic handle boiling water?
Not for long. Boiling water at 212 °F (100 °C) is above every maker's continuous service rating and at or above the heat deflection temperature, so it can warp thin parts and stress joints. Brief splashes are usually fine.
Is cast acrylic more heat resistant than extruded?
Yes, modestly. Acrylite rates cast sheet for 180 °F continuous with a Vicat point of 239 °F, versus 160 °F and 220 °F for its extruded sheet. Cast also forms at higher temperatures and has a wider forming window.
Are fumes from overheated acrylic dangerous?
Overheated or burning acrylic releases irritating fumes, mostly methyl methacrylate monomer, and burning in low air also makes carbon monoxide. Ventilate well and don't breathe them. See are laser-cut acrylic fumes toxic.
What is the melting point of acrylic in Celsius?
There isn't a true one. The useful numbers are the Vicat softening point, about 105 °C for extruded and 115 °C for cast sheet, and the forming range of roughly 150 to 190 °C. Some resin data quote a "melt" processing range above that, but sheet starts decomposing above about 300 °C.
Sources
- Röhm/Polyvantis: ACRYLITE cell cast sheet (GP) technical information
- Röhm/Polyvantis: ACRYLITE premium (FF) technical information
- Röhm: PLEXIGLAS GS/XT technical information 211-1
- Plaskolite: OPTIX-L continuous cast acrylic sheet fabrication guide
- Arkema: Plexiglas G acrylic sheet material safety data sheet (Temple University copy)