Acrylic vs Polycarbonate (Lexan): Which Plastic for Your Project?
Clear Conclusion
For most indoor display, signage, optical, and retail projects, acrylic (PMMA) is the practical choice: higher optical clarity, better native scratch resistance, better inherent UV stability, easier edge polishing, and lower material cost. Choose polycarbonate (PC, commonly sold under the Lexan brand) when the primary requirements are high impact resistance, higher continuous service temperature, or safety glazing that must resist shattering.
This ranking holds under typical commercial sheet grades and standard room-temperature test conditions. Actual performance depends on specific grade, thickness, UV stabilizers, hard coats, and the exact test method used.
What Each Material Is
Acrylic is polymethyl methacrylate (PMMA). It is an amorphous thermoplastic known for high light transmission, a hard surface, and good weatherability in standard grades. Polycarbonate is an amorphous engineering thermoplastic (often associated with the Lexan brand) valued for toughness and higher heat resistance. Both are transparent thermoplastics used as glass substitutes, but they differ in molecular structure and therefore in impact behavior, surface hardness, and long-term outdoor appearance.
Neither material is universally superior. The right choice depends on which properties dominate the application: optical quality and surface durability, or impact and thermal performance.
Structured Comparison
The table below summarizes commonly reported ranges from commercial sheet data sheets under standard ASTM test conditions. Values vary by manufacturer, grade, thickness, and exact test protocol. They are indicative only and should not be treated as design allowables without the specific material certificate.
| Property | Acrylic (PMMA) | Polycarbonate (PC / Lexan) | Typical Test Reference |
|---|---|---|---|
| Light transmission (clear sheet) | Typically 91–93% | Typically 86–90% | ASTM D1003 |
| Notched Izod impact | Low (commonly ~0.3–0.4 ft-lb/in range) | High (commonly ~12–16 ft-lb/in range) | ASTM D256 |
| Surface hardness / scratch resistance | Higher (harder surface; scratches can often be polished) | Lower (softer surface; often needs hard coat for abrasion resistance) | Rockwell / pencil hardness |
| UV / outdoor clarity retention (uncoated) | Generally good inherent stability | Usually requires UV-stabilized grade or coating to limit yellowing | Outdoor exposure / QUV |
| Heat deflection / continuous service temperature | Lower (typical continuous service often cited near 70–80 °C depending on grade) | Higher (typical continuous service often cited near 110–120 °C depending on grade) | ASTM D648 / manufacturer data |
| Relative material cost (same thickness) | Usually lower | Usually higher | Market pricing |
| Edge polish / fabrication for optical finish | Excellent (diamond or flame polish to high clarity) | More limited (edges do not polish to the same optical quality) | Fabrication practice |
Key Property Differences
Optical Clarity
Clear acrylic sheet commonly transmits a higher percentage of visible light than standard clear polycarbonate under ASTM D1003 conditions. The difference is often small in a single thin sheet but becomes noticeable in thicker parts, multi-layer assemblies, or applications where maximum light throughput or color neutrality matters (displays, lenses, light guides). Acrylic also accepts high-quality edge polishing more readily.
Impact Resistance
Polycarbonate is the tougher material. It absorbs energy by yielding and deforming rather than fracturing in a brittle manner under many impact conditions. Acrylic can crack or shatter under sufficiently high impact, although fragments are typically less sharp than glass. For machine guards, safety glazing, or areas subject to vandalism or debris, polycarbonate (or a UV-stabilized grade of it) is usually preferred.
UV Stability and Outdoor Use
Standard acrylic grades retain optical clarity outdoors for extended periods without additional coatings. Uncoated polycarbonate tends to yellow and lose transmission under prolonged UV exposure; outdoor polycarbonate applications therefore normally specify UV-stabilized grades or co-extruded protective layers. When long-term appearance is the priority and impact loads are moderate, acrylic is frequently selected for outdoor signage and architectural glazing.
Thermal Performance
Polycarbonate generally offers a higher heat-deflection temperature and higher continuous service temperature range. It is the more suitable choice near heat sources, under high-intensity lighting, or in environments with elevated ambient temperatures. Acrylic is adequate for most indoor and moderate outdoor conditions.
Fabrication Notes
Both materials can be CNC-machined, laser-cut (with process differences), thermoformed, and bonded. Acrylic solvent-bonds readily and finishes to a high optical edge. Polycarbonate is more ductile during machining but requires care with solvents and benefits from hard coatings when abrasion resistance is required. Laser-cut acrylic edges often polish cleanly; polycarbonate edges may show discoloration or require different finishing.
Scenario-Based Recommendations
Retail displays, cosmetic organizers, product risers, and signage — Acrylic. Clarity, polishability, and cost favor PMMA. Custom acrylic fabrication is widely available for these applications.
Machine guards, security glazing, impact-prone enclosures — Polycarbonate. Impact performance dominates.
Outdoor signs and architectural panels with low impact risk — Acrylic (or UV-stabilized acrylic). Inherent weatherability reduces the need for coatings.
Outdoor panels subject to hail, vandalism, or debris — UV-stabilized polycarbonate.
Parts near heat sources or requiring higher continuous temperature — Polycarbonate.
Optical lenses, light guides, or high-clarity covers — Acrylic, provided impact requirements are modest.
Hybrid approaches (polycarbonate core with an acrylic or hard-coat surface) exist for applications that need both toughness and surface durability, but they add cost and complexity.
FAQ
Is polycarbonate always stronger than acrylic?
In notched impact tests under standard conditions, polycarbonate is substantially tougher. “Stronger” depends on the loading mode: acrylic can show higher tensile or flexural modulus in some data sets. Always check the relevant property and grade.
Which material is clearer?
Clear acrylic sheet typically shows higher light transmission and is preferred when maximum optical clarity and edge finish matter.
Does polycarbonate yellow outdoors?
Standard uncoated polycarbonate can yellow under prolonged UV exposure. Specify UV-stabilized grades or coated sheet for outdoor use. Acrylic is more inherently stable in this regard.
Can I substitute one for the other without redesign?
Not always. Differences in impact behavior, thermal expansion, solvent resistance, and edge finishing mean a direct swap can affect durability, appearance, or assembly method.
Which is more cost-effective for custom displays?
Acrylic is usually lower in material cost and easier to polish to a retail finish, making it the default for most custom display, box, and tray programs.
References
ASTM D1003 – Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics. ASTM
ASTM D256 – Standard Test Methods for Determining the Izod Pendulum Impact Resistance of Plastics. ASTM
ASTM D648 – Standard Test Method for Deflection Temperature of Plastics Under Flexural Load. ASTM
Typical commercial sheet property ranges are drawn from manufacturer data sheets published under the above ASTM methods. Always request the current technical data sheet and material certificate for the specific grade under consideration.