PMMA (Acrylic)
A glass-clear plastic
Typical values for the temper in the title
PMMA (polymethyl methacrylate, "acrylic", "Plexiglas") is the clearest plastic: it transmits light like glass or better, and is highly resistant to UV and weather without yellowing. It is harder and more scratch resistant than polycarbonate, and easy to polish.
Its drawback is brittleness: under a strong impact it cracks and breaks. It is used for windows, signs and displays, lenses and light guides, aquariums and lighting covers.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 72 MPa | |
| Elongation A | 5% | |
| Modulus of elasticity E | 3.2 GPa | |
| Density ρ | 1.19 g/cm³ | |
| Max continuous service temperature | 90°C | |
| Heat deflection temperature (HDT) | 100°C | |
| Machinability | 80% | relative rating in the site database |
Structure and family
| Feature | Value | Meaning |
|---|---|---|
| Type | amorphous thermoplastic, transparent | clarity and UV resistance |
| Tg glass transition | about 105 °C | |
| Light transmission | very high |
Typical values per producer data sheets.
Grades and versions
In engineering polymers, the choice is between an unfilled grade, filled grades (glass or carbon fiber) and special grades (bearing, medical, food). Filler strongly changes strength, stiffness and expansion.
| Version | Properties | When to choose it |
|---|---|---|
| Cast | high clarity and optical quality, good for machining | sheets for machining, displays |
| Extruded | cheaper, uniform dimensions | general sheet |
| Impact modified | more ductile | light guarding |
Applications
- Windows and partitions
- Signs and displays
- Lenses and light guides
- Aquariums
- Lighting covers
Fabrication
Machining and cutting
Easy to machine, laser cut and polish. Cast sheet gives nicer polished edges.
Crazing
Sensitive to crazing from stresses and solvents (such as alcohol). After machining, annealing is sometimes performed.
Thermal expansion
The expansion coefficient of an unfilled polymer is several times that of a metal. In a precision part or an assembly with metal, design clearances accordingly.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| PC (Polycarbonate) | 65 MPa | Ultrasonic | PC: far more impact resistant, scratches and yellows more · material page |
| ABS | 45 MPa | Ultrasonic | ABS: opaque, tough · material page |
| PSU (Polysulfone) | 70 MPa | Ultrasonic | PSU: transparent and heat resistant · material page |
Common mistakes
Using PMMA where there is an impact hazard
It is brittle. For guarding, PC.
Cleaning with alcohol or a solvent
Causes crazing.
Drilling without cooling and with an unsuitable drill
It cracks around the hole.
Equivalents, standards and supply
| ISO | PMMA |
|---|---|
| ASTM | D788 |
| Standards | ASTM D788 |
| Forms | plate · rod · pellets |
| Producers | Röhm Plexiglas · Arkema Altuglas · Mitsubishi Shinkolite |
Learn more
Values are typical for an unfilled grade (unless stated otherwise) and for comparison only. In polymers, properties depend on grade, filler, temperature, moisture and load duration. For design, rely on the producer data sheet for the specific grade. Sources: ASTM classification standards (D8033, D5205, D5204, D6394, D4067 and others), producer data sheets, and the METAL HUB materials database.
Updated: October 31, 2026