PC vs PMMA

Foreword

Polycarbonate (PC resin) and polymethyl methacrylate (PMMA), also known as “acrylic,” are two widely used transparent thermoplastic resins. Both resins offer excellent optical properties, making them ideal choices for lampshades, protective covers, display stands, equipment components, automotive applications, and more.

However, PC and PMMA are not interchangeable in many applications; the two resins differ significantly in terms of impact strength, weather resistance, surface hardness, chemical resistance, and temperature resistance.

Therefore, it is crucial to understand the differences between these two resins before using PC resin and PMMA.

PC vs. PMMA: A Brief Comparison

1. Transparency and Optical Properties

Both PC resin and PMMA resins are highly transparent engineering plastics, and to the naked eye, there is generally no discernible difference between them; however, compared to polycarbonate, PMMA resin offers higher transparency and better optical properties.

• General-purpose PMMA resin has a light transmittance of 90–92%, which is similar to that of glass. It is commonly used for display panels, lampshades, advertising signs, and decorative components.
• PC resin also offers good transparency; general-purpose PC resin has a light transmittance of 85–90%, which is slightly lower than that of PMMA, but its advantages lie primarily in its flexibility and impact resistance. It is commonly used for equipment viewing windows, safety guards, and automotive lamp covers.

2. Impact resistance: One of the key properties of PC material

• PC is a widely used thermoplastic engineering plastic due to its excellent flexibility and impact resistance; it can withstand impact forces that would cause conventional acrylic to crack or even shatter. Conventional PC resin has an Izod notched impact strength of 50–80 kJ/m² at 23°C, making it particularly suitable for applications with high impact resistance requirements, such as safety shields, safety windows for machinery, and enclosures for electronic and electrical equipment.
• PMMA, on the other hand, has greater rigidity and higher hardness, but its Izod notched impact strength is only 1.5–3 kJ/m², making it more brittle and unsuitable for applications requiring impact resistance.

As shown in the figure on the right, when PC sheets (left) and acrylic sheets (right) of the same 8 mm thickness were tested with the same impact force, the PMMA sheet shattered noticeably, while the PC sheet remained largely intact, with no cracks.

Due to their high rigidity and brittleness, PMMA sheets exhibit distinct fracture characteristics when subjected to impact. The fracture propagates radially outward from the point of impact; a noticeable whitening occurs near the impact point, and the fractured edges are clean with sharp, well-defined edges.

3. Flame-retardant properties

Both PC resin and acrylic are thermoplastic engineering plastics that can be ignited, but they differ in how easily they catch fire.

The molecular chains of PC material contain aromatic structures and carbonate groups; when exposed to a flame, they form a black carbon layer that prevents further burning, release a distinct odor, and do not exhibit significant dripping.

Standard polycarbonate materials do not meet the UL 94 V0 flame-retardant rating. If you require a high-performance flame-retardant PC resin, please consider👉Sabic Lexan 940A PC, a transparent, high-performance polycarbonate material with the UL 94 V-0 flame-retardant rating @ 1.5 mm thickness. Ideal for thin-walled, high-performance flame-retardant applications

When PMMA burns, the flame does not go out on its own but continues to burn. A large number of bubbles form at the point of combustion, and the material drips as it burns, releasing a pungent odor.

4. Hardness and Scratch Resistance: Obvious Defects in PC Material

Although PC material is characterized by its resistance to bending and high flexibility, its low hardness means it can develop noticeable scratches even when scraped by relatively soft objects such as fingernails or sand. To address the scratch-prone nature of PC sheets, a wear-resistant film is typically applied to their surface, or a more abrasion-resistant material—such as Teijin Panlite PC resin—is selected during the material selection process.

Acrylic sheets, on the other hand, are relatively hard and offer better scratch resistance. They are also generally less sensitive to UV radiation and do not yellow after prolonged exposure to sunlight outdoors, unlike solid PC sheets; this makes them the material of choice for applications with high aesthetic requirements.

5. Comparison of Temperature Resistance: PC Resin vs. Acrylic

Compared to common, unmodified, general-purpose materials

Heat propertie	PC resin	PMMA(acrylic)
Glass Transition Temperature Tg	145-150℃	105-120℃
Vicat softening temperature	140-155℃	100-110℃
Heat deflection temperature @ 0.45 MPa	130-140℃	95-105℃
Heat deflection temperature @ 1.8 MPa	120-130℃	90-100℃

Under the same test conditions, the heat resistance of general-purpose unfilled PC resin is generally 25–40°C higher than that of general-purpose PMMA, making it more suitable for high-temperature applications and those requiring heat dissipation, such as housings for home appliances, equipment viewing windows, automotive instrument panel housings, and automotive headlights that require high heat resistance.

How to Choose Between PC Resin and PMMA:

PC and PMMA are not interchangeable materials; the choice of material depends on your application requirements.

When choosing PC resin, your requirements should be:

• High impact resistance
• High flexibility; the product requires bending
• High heat resistance
• Flame-retardant properties

When selecting PMMA material, your requirements should be:

• Exceptional clarity
• Greater hardness
• Scratch resistance
• Improved surface gloss
• No noticeable discoloration over time