When you need clear plastic parts, two materials often come to mind: polycarbonate (PC) and acrylic (PMMA). Both are transparent and can be injection molded. But they have very different properties. Choosing the right one affects strength, clarity, cost, and durability. In this guide, we compare polycarbonate vs acrylic for injection molding. You will learn about their key differences, when to use each, and how to avoid common mistakes. Whether you need lenses, displays, or housings, this article helps you decide.
Overview of Polycarbonate (PC)
Polycarbonate is a strong, transparent engineering plastic. It is known for its high impact resistance and heat tolerance.
Key Properties of PC
- Impact resistance: PC is virtually unbreakable. It can withstand heavy blows without cracking.
- Heat resistance: Withstands continuous use up to 130°C. Good for applications that get warm.
- Optical clarity: Light transmission is about 88–90%. Slightly lower than acrylic, but still clear.
- Chemical resistance: Poor resistance to solvents and alkalis. Can crack under stress with certain chemicals.
- UV sensitivity: Unprotected PC yellows in sunlight. UV-stabilized grades are available.
Common Applications of PC
- Safety glasses, face shields
- Electronic device housings
- Automotive headlamp lenses
- Medical device components
- Impact-resistant glazing
Overview of Acrylic (PMMA)
Acrylic, also known as PMMA, is a lightweight, rigid transparent plastic. It is often used as a glass substitute.
Key Properties of PMMA
- Optical clarity: PMMA has excellent transparency – about 92% light transmission. It is clearer than PC.
- Impact resistance: PMMA is stronger than glass but much less impact-resistant than PC. It can crack or shatter under strong impact.
- Weather resistance: PMMA has good UV resistance. It does not yellow easily in sunlight.
- Surface hardness: PMMA is scratch-resistant, but not as hard as glass.
- Chemical resistance: Poor resistance to solvents, but better than PC against some cleaners.
Common Applications of PMMA
- Display screens, signage
- Light covers, lenses
- Aquariums, skylights
- Automotive tail lights
- Cosmetic packaging
Head-to-Head Comparison: PC vs Acrylic
| Property | Polycarbonate (PC) | Acrylic (PMMA) | Winner |
|---|---|---|---|
| Impact strength | Very high – 250x stronger than glass | Moderate – 10x stronger than glass | PC |
| Optical clarity | 88–90% transmission | 92% transmission | Acrylic |
| Heat resistance | Up to 130°C | Up to 80–100°C | PC |
| UV resistance | Poor (needs UV stabilizer) | Good | Acrylic |
| Scratch resistance | Low (scratches easily) | Moderate | Acrylic |
| Cost | Higher | Lower | Acrylic |
| Ease of molding | Needs higher temperatures, dries slower | Easier to mold, faster cycles | Acrylic |
| Chemical resistance | Sensitive to solvents | Also sensitive, but slightly better with mild cleaners | Tie |
Real‑scenario risk: A client once chose acrylic for a protective shield that required high impact resistance. The parts cracked during shipping. We recommended PC, and the problem was solved. Always match the material to the mechanical demands.
When to Choose Polycarbonate
Choose PC when:
- The part must withstand high impact or mechanical stress.
- The operating temperature exceeds 80°C.
- You need flame-retardant grades (UL94 V-0 available).
- The part will be used in safety-critical applications (e.g., machine guards, goggles).
Example: A manufacturer needed a transparent housing for an outdoor electrical enclosure. The enclosure faced occasional impacts and high heat. PC with UV stabilizer was the right choice.
When to Choose Acrylic
Choose acrylic when:
- Optical clarity is the top priority.
- The part will be exposed to sunlight for long periods.
- Cost is a major concern.
- The part does not need high impact strength.
- You need good surface hardness and scratch resistance.
Example: A point-of-sale display required a crystal-clear front panel. Acrylic provided the clarity and UV stability at a lower cost than PC.
Injection Molding Considerations for PC and Acrylic
Drying
- PC: Must be dried thoroughly (120°C for 4 hours) to prevent splay and bubbles.
- Acrylic: Also needs drying (80–90°C for 2–4 hours) to avoid surface defects.
Melt Temperature
- PC: 280–320°C. Higher temperature requires more energy and tooling care.
- Acrylic: 210–250°C. Easier on molds.
Mold Temperature
- PC: 80–120°C to achieve good surface finish and reduce stress.
- Acrylic: 40–80°C. Cooler molds work well.
Shrinkage
- PC: 0.5–0.7%
- Acrylic: 0.3–0.6%
Both materials require careful gate and vent design. For more details on material selection, see our injection molding material selection guide.
Cost Comparison
Acrylic is generally 20–30% cheaper than polycarbonate on a per‑kilogram basis. However, total part cost also depends on cycle time and yield. PC may require longer cycles and higher energy, but its durability can reduce replacement costs in the field.
Which One Is Right for Your Project?
Ask these questions:
- Will the part be dropped or hit? → PC
- Does it need to stay crystal clear for years outdoors? → Acrylic
- Is heat resistance critical? → PC
- Is cost the main driver? → Acrylic
- Does it need to be flame retardant? → PC (special grades)
Still unsure? Our engineers can review your application and recommend the best material. Learn more about our polycarbonate injection molding services.
Frequently Asked Questions
Q1: Is acrylic or polycarbonate more scratch-resistant?
A: Acrylic is more scratch-resistant than polycarbonate. However, both can be coated for improved scratch resistance.
Q2: Can I use acrylic for outdoor applications?
A: Yes, acrylic has excellent UV resistance and does not yellow easily. It is a good choice for outdoor signs and displays.
Q3: Which material is easier to injection mold?
A: Acrylic is generally easier to mold because it flows better at lower temperatures. PC requires higher temperatures and more precise control.
Q4: Are there food-grade versions of PC and acrylic?
A: Yes, both materials have FDA-approved grades for food contact. Always specify the correct grade.
Q5: Can PC and acrylic be bonded or welded?
A: Both can be solvent bonded, ultrasonic welded, or adhesively bonded. However, PC bonds more easily than acrylic.
Q6: Which is better for LED light covers?
A: Acrylic is often preferred for light covers because of its higher clarity and light transmission. PC is used where impact resistance is critical.
Summary
Polycarbonate and acrylic are both excellent transparent materials, but they serve different needs. PC offers unmatched impact strength and heat resistance, while acrylic provides superior clarity, UV stability, and lower cost. By understanding your application requirements, you can make the right choice.
At Miracles Manufacturing, we specialize in molding both PC and acrylic parts. Whether you need prototypes or high-volume production, we have the expertise to deliver quality components. Contact us today to discuss your project.
