Technically Speaking | 4 APRIL 2025

Transparency in Thermoplastics

Tech Tips from Our Engineers at Bamberger Amco Polymers

Thermoplastic transparency plays a crucial role in the design and functionality of products across packaging, medical, lighting, automotive, and consumer goods industries. Whether you're selecting a material for a clear face shield, a cosmetic bottle, or LED lighting covers, understanding optical properties is essential.

Key Optical Properties of Thermoplastics

Transparency in thermoplastics is determined by how light interacts with the material. These interactions are measured through optical properties such as:

• Light Transmission (%) – The percentage of light that passes through a plastic.
• Haze – The degree to which the light is scattered, reducing visual clarity.
• Gloss – The surface's ability to reflect light.
• Refractive Index – How much the plastic bends or refracts light.

Key takeaway: Even plastics with high light transmission can appear cloudy if haze is not controlled.

Common Transparency Terms in Plastics

• Transparent Thermoplastics: Materials like polycarbonate or acrylic allow for high light transmission with minimal scattering. These are ideal for lenses, screens, and protective covers. An observer can see clearly through it.​
• Translucent Plastics: This material's physical properties let light pass through, but in different scattered directions. This creates a blurred or diffused visual effect, often used in applications like light diffusers, LED housings, and consumer packaging.
• Opaque Plastics: These materials don't let any light pass through them. Used where light-blocking is required—think automotive interiors, electronic housings, or medical devices where visibility is not desired. Objects behind them are practically invisible to a viewer.

Factors that Can Influence Thermoplastic Opacity

• Fillers and Additives - Additives like glass fiber or talc reduce light transmission and increase haze.
• Plastic Thickness - Thicker sections scatter more light, even in clear materials.
• Clarifiers and Nucleating Agents - Used to reduce haze and increase transparency in semi-crystalline plastics like polypropylene (PP)
• Masterbatch Coloring

Thermoplastics with High Transparency

These plastics are commonly used where optical clarity is essential:

• Acrylic (PMMA) – Excellent clarity and weatherability. Ideal for display windows and signage.
• Polycarbonate (PC) – High impact resistance with good transparency. Common in safety goggles and automotive headlamps.
• PET/PETG – Great for packaging, clamshells, and medical trays.
• Polystyrene (PS) – Good clarity, often used in disposable packaging and labware.

Thermoplastics with Low Transparency

These materials are typically opaque or translucent:

• ABS (Acrylonitrile Butadiene Styrene): High impact strength, limited transparency.
• PA6 / PA66 (Nylon): High crystallinity, generally opaque.
• POM (Acetal): Excellent mechanical properties, but low light transmission.
• PPS / PTFE: Engineering polymers designed for high-performance rather than clarity.

How Transparency is Measured

A polymer's opacity measurements can be calculated through direct observation, using mathematical equations to quantify the light that's passing through it.

• Spectrophotometers: Measure % light transmission, haze, and color in accordance with standards like ASTM D1003.
• Gloss Meters: Evaluate surface reflectivity.
• Visual Comparison: Can be used for initial assessments but lacks quantifiable accuracy.

Choosing the Right Transparent Plastic

When selecting a transparent thermoplastic, consider your application's mechanical, environmental, and aesthetic requirements. Factors like impact strength, UV resistance, and chemical compatibility can significantly affect long-term optical performance. Our technical team can help you select the right material for your application.

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