PC (Polycarbonate) vs PMMA (Acrylic): Optical Plastic Comparison
Published: 2026-06-02
PC and PMMA are the two dominant transparent engineering plastics, selected based on a trade-off between impact resistance (PC) and surface hardness/optical clarity (PMMA). PMMA transmits 92% visible light vs 88% for PC, and PMMA's surface...
PC and PMMA are the two dominant transparent engineering plastics, selected based on a trade-off between impact resistance (PC) and surface hardness/optical clarity (PMMA). PMMA transmits 92% visible light vs 88% for PC, and PMMA's surface hardness (Rockwell M95) is significantly higher than PC (M70) — PMMA resists scratching in applications like display windows and instrument panels. PC's defining advantage: impact strength >700 J/m vs PMMA's 15-20 J/m — PC is essentially unbreakable in standard tests while PMMA is brittle. This makes PC the only choice for safety-critical transparent components (machine guards, face shields, aircraft windows).
Weathering: PMMA has inherently superior UV resistance — it does not yellow or embrittle after decades of outdoor exposure. Standard PC yellows significantly within 2-3 years of outdoor UV exposure unless UV-stabilized grades are specified. For outdoor transparent applications (skylights, signage), PMMA is preferred. For applications requiring both transparency and impact resistance (automotive headlamp lenses), PC with a UV-curable hard coat (silicone-based) provides the best of both materials — PC's impact strength plus the hard coat's UV protection and scratch resistance.
Comparison at a Glance
| Tensile Strength | PC: 65 MPa vs PMMA: 70 MPa |
|---|---|
| Melting Point | PC: Amorphous (Tg 147°C) vs PMMA: Amorphous (Tg 105°C) |
| Shrinkage Rate | PC: 0.6% vs PMMA: 0.4% |
| Flexural Modulus | PC: 2.3 GPa vs PMMA: 3.0 GPa |
| Hdt | PC: 135°C vs PMMA: 95°C (at 1.82 MPa) |
Equivalents & Cross-References
| Equivalent / Alternate | Action |
|---|---|
| Makrolon vs Plexiglas | |
| Lexan vs Acrylite |
Frequently Asked Questions
Can PC and PMMA be bonded together?
Yes, with solvent bonding using methylene chloride or specialized acrylic adhesives. However, the difference in thermal expansion (PC CTE 65 × 10⁻⁶/K vs PMMA 70 × 10⁻⁶/K) is small enough that thermal cycling does not cause delamination in most applications. UV-curable optical adhesives provide the clearest bond line for optical applications.
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References & Industry Standards
- ASTM International. Standard Specifications for Engineering Plastics & Thermoplastics. astm.org
- UL Prospector. Plastics & Elastomers Material Database. ulprospector.com
- MatWeb. Material Property Data for Engineering Thermoplastics. matweb.com
- ISO 1043. Plastics — Symbols and Abbreviated Terms. iso.org