Key Differences and Best Uses

Engineers and manufacturers know the choice of plastic material can make or break a project. Enter PETG (Polyethylene Terephthalate Glycol) and polycarbonate (PC), two high-performance thermoplastics that are as versatile as they are widely used. Their durability, clarity, and versatility make them stand out, but it's their unique characteristics that set them apart for different applications.

In this article, we’ll compare PETG and polycarbonate in depth, delving into their properties, performance metrics, safety concerns, and cost considerations to help you make an informed decision.

Introduction to PETG and Polycarbonate

PETG is a modified form of PET (Polyethylene Terephthalate) created by adding glycol. This prevents crystallization during heat processing, enhancing the material’s toughness and impact resistance. PETG is an amorphous copolyester with excellent optical clarity, chemical resistance, and formability, making it a go-to material for applications in packaging, medical devices, displays, and more.

Polycarbonate (PC) is an engineering-grade thermoplastic synthesized from bisphenol A and phosgene, with carbonate groups in its molecular chain. Known for its extreme toughness and optical clarity, polycarbonate is often used in applications where impact strength, temperature resistance, and dimensional stability are critical. Due to its superior performance under stress and in high-temperature environments, it is widely used in the automotive, electronics, and construction industries.

Material Properties: PETG vs. Polycarbonate

When choosing between PETG and polycarbonate, it’s critical to understand their key physical properties and how they perform under various conditions. Please note, the technical information listed below may vary. Please contact your local Piedmont Plastics sales representative for specific material properties.

Impact Strength

• Polycarbonate: Polycarbonate is notable for its unmatched impact resistance, which is measured to be between 12.0 and 16.0 ft-lbs/in of notch, making it up to 200 times stronger than glass. This extreme toughness allows it to be used in safety-critical applications such as bulletproof windows, riot shields, and automotive lighting systems. Polycarbonate maintains its structural integrity even under high stress, making it highly dependable in demanding environments.

• PETG: While PETG has respectable impact resistance (around 1.7 ft-lbs/in of notch), it doesn’t match polycarbonate’s extreme toughness. However, its impact strength is still superior to materials like acrylic, making it a popular choice for applications that require moderate durability, such as protective packaging, medical containers, and cosmetic displays. PETG’s balance of impact strength and flexibility makes it suitable for various general-purpose uses, though it may not withstand heavy or repeated loads as well as polycarbonate.

Heat Resistance

• Polycarbonate: Polycarbonate is well-known for its thermal stability, with a heat deflection temperature (HDT) ranging from 125°C to 135°C, depending on the grade. This makes it suitable for applications exposed to high temperatures, such as automotive components, electronic housings, and light covers. Polycarbonate retains its optical clarity and mechanical strength even when exposed to prolonged heat, making it the go-to material for high-temperature environments.

• PETG: PETG has a significantly lower heat deflection temperature, generally between 70°C and 75°C. While this makes it adequate for many general-purpose uses, it is less suitable for environments where high temperatures are common. For instance, polycarbonate is the better choice in industrial settings where parts are regularly exposed to heat. However, PETG works well in lower-temperature environments, such as signage, medical packaging, and consumer products that do not experience extreme heat.

Chemical Resistance

• PETG: One of PETG’s standout features is its excellent chemical resistance. It resists a wide range of chemicals, including alcohols, acids, and mild solvents, without suffering degradation. This makes it an ideal material for use in chemical-rich environments, such as medical and pharmaceutical packaging, where sterilization is required. PETG also performs well in food-contact applications, as it is both BPA-free and FDA-approved for food safety, making it a top choice for food containers and packaging.

• Polycarbonate: While polycarbonate is durable in many respects, it has poor chemical resistance to substances like esters, ketones, and aromatic solvents. Over time, exposure to these chemicals can cause polycarbonate to degrade, crack, or become cloudy. Therefore, if chemical exposure is a concern, PETG is typically more reliable, especially in environments where resistance to aggressive cleaning agents or sterilization chemicals is necessary.

Clarity and Transparency

• Polycarbonate: Polycarbonate is often used as a glass substitute due to its excellent light transmission properties. It is highly transparent, with an optical clarity that rivals glass, making it ideal for applications where visibility is key, such as optical lenses, automotive lighting, and protective windows. One downside is that polycarbonate can be yellowed over time if exposed to prolonged UV light unless coated with UV inhibitors.

• PETG: PETG also offers excellent optical clarity, though it is slightly less transparent than polycarbonate. It has a lower refractive index, making it a suitable material for clear packaging, cosmetic containers, and displays. PETG does not yellow as quickly as polycarbonate when exposed to sunlight, making it a better choice for outdoor applications that don’t require extreme toughness or heat resistance.

Safety and Health Considerations

• PETG: PETG is widely considered safe for food and medical applications. As a BPA-free material, PETG is often the preferred choice in industries that require compliance with FDA regulations, such as food containers, medical packaging, and cosmetic products. Additionally, PETG’s chemical stability ensures that it does not release harmful substances during processing or use.

• Polycarbonate: While polycarbonate is a high-performance material, its use of Bisphenol A (BPA) has raised concerns in some sectors, particularly in food and medical use. BPA is known to have potential health risks if it leaches into food or beverages, which has led to a preference for PETG in applications where food safety is critical. However, polycarbonate is still widely used in non-food applications where its superior strength and heat resistance are necessary, such as in electronics and construction.

Environmental Impact and Recyclability

• PETG: PETG is fully recyclable and can be processed through existing PET recycling streams in most states. (Plastic Code 1). However, some states do list it under Plastic Code 7. Its chemical structure allows it to maintain its stability during recycling, making it a more sustainable option, especially in industries focused on environmental responsibility. PETG’s use in packaging has been growing, particularly as companies prioritize sustainability and using recyclable materials.

• Polycarbonate: Polycarbonate is also recyclable (Plastic Code 7), but the process is more complex due to the potential presence of additives such as BPA, flame retardants, and UV stabilizers. These additives can complicate the recycling process and make it less cost-effective. Furthermore, the environmental concerns surrounding BPA have led some industries to move away from polycarbonate, particularly in packaging and consumer products.

Cost Comparison

• PETG: PETG is typically more affordable than polycarbonate, making it an attractive option for high-volume applications such as packaging, consumer goods, and medical devices. Its ease of processing and lower cost make PETG a preferred choice for manufacturers looking to balance performance with cost-effectiveness.

• Polycarbonate: Polycarbonate is more expensive, primarily due to its superior impact resistance and heat tolerance. While the higher cost may not work for applications with moderate performance requirements, polycarbonate remains the material of choice for critical, high-stress applications where strength and durability are paramount.

Applications & Uses

• Polycarbonate is best suited for high-impact, high-heat environments. Applications include bulletproof glass, automotive parts, optical lenses, electronic enclosures, and machine guards.

• PETG is ideal for applications requiring moderate durability, chemical resistance, and ease of processing. Common uses include food containers, medical packaging, displays, cosmetic containers, and outdoor signage.

Which Material Should You Choose?

When it comes to choosing between PETG and polycarbonate, it really depends on what your project needs. If you’re working in high-impact, high-heat environments where toughness and temperature resistance are essential, polycarbonate is the way to go. Its durability makes it perfect for heavy-duty applications.

On the other hand, if you’re looking for a material that’s easy to work with, resistant to chemicals, and safe for food or medical use, PETG is a versatile and cost-effective choice.

At Piedmont Plastics, we offer both PETG and polycarbonate materials to fit a wide range of applications. Whether you’re working on industrial parts, medical packaging, or consumer products, our knowledgeable team is here to help you find the perfect material for your project.