Material guide
PMMA, polymethyl methacrylate
PMMA, polymethyl methacrylate, is acrylic, the plastic with the clarity of glass and a hard, glossy surface that stands up to scratches. Chosen for signs, displays and optical parts where the looks have to last. It comes both cast and extruded, PMMA C and PMMA E.
What it is
PMMA, polymethyl methacrylate, is what most people call acrylic in everyday speech. It is the most transparent of the common plastics, with light transmission on a par with glass and a hard surface that stays glossy and takes scratches better than most transparent plastics. Acrylic is dimensionally stable, easy to mill, laser cut and polish to a glossy edge, and it takes color and machining beautifully. That makes it an obvious choice where the looks and the optics are the whole point. The material comes in two forms, one cast and one extruded, described further down.
Properties
Very transparent, clarity on a par with glass
Good scratch resistance compared with other transparent plastics
Dimensionally accurate in machining, keeps its shape
Easy to mill, laser cut and polish to a glossy edge
Takes color and finish well, glossy or matte surface
Does not yellow in sunlight the way many other plastics do
Common applications
PMMA sits in signs, displays, showcases, light boxes, lenses and cover panels where clarity and a glossy surface decide the job. It is common in shop fittings and exhibition work, in lighting where the light is to be diffused or guided, and in machine fronts and doors where you want to see through to a good looking surface. When the looks and the optics weigh heaviest, the choice often lands on acrylic. Outdoors, acrylic sits in roof lights, greenhouses and shop windows, and in aquariums and pools where you both want to see through and want to avoid the weight of glass. An acrylic sheet weighs about half as much as a glass sheet of the same thickness.
Limitations
Acrylic is hard but more brittle than polycarbonate; it can crack from a blow where PC simply absorbs it, so for parts that have to take serious mechanical punishment you pick polycarbonate instead. It is not a high temperature material either, and it copes poorly with even moderate solvents; some chemicals leave the surface cloudy or brittle. For a surface that has to handle both impact and scratches, you have to weigh the scratch resistance of acrylic against the impact resistance of polycarbonate. On the other hand, acrylic stands up to sun and weather better than most see-through plastics and yellows more slowly, which is why it holds up outdoors year after year.
For short periods our acrylic grades take 90 °C, and downward they go to -40 °C. The continuous service temperature differs between cast and extruded acrylic, so ask us if the part is going to sit somewhere hot.
Grades and variants
Acrylic comes in a cast and an extruded form, and they differ in machining and price. Beyond that there are colored, matte surface and light diffusing grades as well as recycled variants.
Base grades
- PMMA C, cast acrylic (Akryl Gjuten). It takes machining, milling and laser cutting somewhat better and comes in more thicknesses and versions. First choice for signs, milled parts and parts that are to be finished afterward.
- PMMA E, extruded acrylic (Akryl Extruderad). More even thickness tolerance and usually better value, good for flat sheets and thermoforming.
Colors and variants
- Colored grades, acrylic in a transparent or colored version to request, for signs and displays.
- Matte surface and light diffusing grades, for signs, displays and lighting where the light is to be diffused.
- Reg variants, recycled material where it fits, for example PMMA C Reg.
A handful of acrylic products come in the shade cream, a specific yellow white tone, but most acrylic variants are transparent or colored to request.
Machining
Acrylic is sawn, milled, drilled and polishes to a completely clear edge, which is the whole point of the material. But it is brittle: drill with low feed pressure, keep the tools sharp and do not clamp it hard. The edge on cast acrylic can be flame polished, extruded is more sensitive.
Formats we can supply
PMMA comes as sheets, round rods and tubes across a wide range of dimensions. You can see formats and dimensions in the range. Do you want a piece cut to size? Enter the dimensions in VisualCutter and you will see the price right away.