Acrylic vs Polycarbonate: 6-Key Differences for Your Project

Which Material Should You Choose?Choose Acrylic (PMMA, if:Display cases, signage, lenses, light guides, picture framing, aquariumsapplications prioritizing optical clarity, scratch resistance, weatherability, and low costChoose Polycarbonate (PC)...

Acrylic (PMMA) and polycarbonate (PC) are the two most-specified transparent engineering plastics, and they are constantly confused because they look almost identical on a showroom shelf — both are clear, rigid, and easily fabricated. But they are engineered for completely different jobs. Acrylic is the optician's plastic: brilliant clarity, scratch resistance, and weatherability at low cost, but it shatters on impact. Polycarbonate is the safety plastic: virtually unbreakable, heat-resistant, and tough, but softer, pricier, and vulnerable to UV yellowing. Choosing the wrong one for a glazing, signage, or protective application leads to either premature breakage (acrylic where impact is expected) or unnecessary cost and scratching (polycarbonate where clarity is paramount). This guide breaks down the six factors that decide the choice, with the property numbers that matter for real projects.

1. Optical Clarity & Light Transmission

Acrylic is the optical champion. Standard cast acrylic transmits 92% of visible light — the highest of any common plastic — and its refractive index (1.49) produces the brilliant, water-clear appearance that makes it the standard for museum display cases, aquarium windows, and LED light guides. Acrylic also retains its clarity over decades of outdoor exposure better than uncoated polycarbonate. Polycarbonate transmits 88-90% of visible light (still excellent, but noticeably less brilliant than acrylic), and its refractive index (1.58) gives it a slightly different visual character. For applications where optical perfection is the priority — lenses, display cases, picture framing, light pipes — acrylic is the right choice. For applications where 'good enough' clarity plus impact resistance is needed — safety glazing, machine guards — polycarbonate wins.

2. Impact Resistance — Polycarbonate's Defining Advantage

This is the single biggest difference between the two materials. Polycarbonate is virtually unbreakable. Its notched Izod impact strength is 600-850 J/m, compared to acrylic's 10-20 J/m — polycarbonate is roughly 30-50x more impact-resistant than acrylic, and 250x more impact-resistant than glass of the same thickness. A 3mm polycarbonate sheet can be hit with a hammer without cracking; a 3mm acrylic sheet will shatter. This is why polycarbonate is the mandated material for safety glazing (face shields, machine guards, motorcycle helmet visors, bullet-resistant windows), while acrylic is never used in impact-critical applications. Acrylic's brittle failure mode is a hard limit — if your part might be struck, dropped, or impacted, acrylic is the wrong choice.

3. Property Comparison Table

Data reflects general-purpose cast acrylic and standard extruded polycarbonate sheet. Specific grades vary. See our pmma-acrylic-guide/">acrylic material guide and pc-polycarbonate-unfilled/">polycarbonate material guide for grade-specific data.

4. Weatherability & UV Resistance

Acrylic is the outdoor champion. Cast acrylic maintains its clarity and mechanical properties for 10-20+ years of outdoor exposure with minimal yellowing — this is why acrylic is the standard for outdoor signage, skylights, and architectural glazing. Polycarbonate, by contrast, yellows and embrittles rapidly under UV exposure unless treated with a UV-absorbing coating or stabilized with HALS (hindered amine light stabilizers). UV-stabilized polycarbonate grades (e.g., Makrolon SLX, Lexan SLX) perform well outdoors, but they cost 2-3x more than standard PC. For outdoor applications without UV protection, acrylic is the default choice. For outdoor applications requiring both impact resistance and UV stability, specify UV-coated polycarbonate and budget for the premium.

5. Machining & Fabrication

Both materials machine well, but with different characteristics. Acrylic machines cleanly with sharp tools, producing smooth edges that can be flame-polished to optical clarity. It cuts, drills, and routes easily, but its brittleness means it can crack if tools are dull or feeds are too aggressive — acute internal corners must be radiused to prevent stress-crack initiation. Polycarbonate is far more forgiving: it machines without chipping, tolerates dull tools better, and bends cold without cracking (acrylic must be heated to bend). Polycarbonate can be cold-formed into tight radii, making it the choice for curved glazing and thermoformed parts. Both materials can be laser-cut, but acrylic produces a flame-polished edge from laser cutting (a significant advantage for signage); polycarbonate's laser-cut edges are slightly rough and may show micro-cracking. For solvent welding, acrylic uses Weld-On 3/4 (methylene chloride-based); polycarbonate uses Weld-On 55. Both bond well with appropriate cements.

6. Price & Cost-Effectiveness

Acrylic is significantly cheaper than polycarbonate. Cast acrylic sheet costs $2-5/kg, while polycarbonate sheet costs $4-8/kg — polycarbonate is roughly 1.5-2x more expensive. For high-volume applications where impact resistance is not required (display cases, picture frames, signage), acrylic's lower cost is a decisive advantage. For applications requiring impact resistance (safety glazing, machine guards), polycarbonate's premium is justified by its 30-50x higher impact strength — using acrylic in an impact-critical application is a safety hazard, regardless of cost savings. The cost decision should always follow the performance decision: first determine whether impact resistance is required, then choose accordingly.

Application Scenarios

When to Choose Acrylic vs Polycarbonate

Choose Acrylic when: (1) optical clarity and brilliance are the top priority — display cases, lenses, light guides; (2) the part will be outdoors without UV coating — signage, skylights, architectural glazing; (3) scratch resistance matters — acrylic's Rockwell M97 hardness resists everyday scratching far better than PC's M70; (4) cost is a primary constraint and impact resistance is not required; (5) the part will be laser-cut — acrylic produces a flame-polished edge, PC does not.

Choose Polycarbonate when: (1) impact resistance is required — safety glazing, face shields, machine guards, helmet visors; (2) the part will see temperatures above 80°C — PC's HDT is 135°C vs acrylic's 95°C; (3) the part requires cold-bending or thermoforming into complex curves; (4) the part is large and shatter-resistance is a safety concern (acrylic shatters into sharp shards); (5) bullet-resistant or forced-entry protection is required (layered PC laminates).

Compare More Materials

For related transparent-plastic comparisons, see our pc-vs-pmma-transparent-plastic/">PC vs PMMA transparent plastic guide, abs-vs-polycarbonate-comparison/">ABS vs Polycarbonate comparison for opaque housing applications, and our polycarbonate vs acrylic automotive guide for vehicle-specific selection. For a deeper look at each material, see our pmma-acrylic-guide/">acrylic (PMMA) material guide and pc-polycarbonate-unfilled/">polycarbonate material guide.

Comparison at a Glance

Equivalents & Cross-References

Related Diagnostics & Materials

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