Transparent Silicone Rubber

What Is Transparent Silicone Rubber?

Transparent silicone rubber is a specialty grade that achieves light transmittance of 90% or higher (measured at 3 mm thickness) while retaining the full thermal, chemical, and biocompatibility properties of standard silicone rubber. The high clarity is achieved through careful selection of high-purity PDMS polymer and fumed silica filler at optimized loading levels, avoiding light-scattering particulates and colored impurities.

Unlike organic plastics such as polycarbonate or acrylic, transparent silicone does not yellow under UV exposure, does not become brittle after thermal aging, and maintains its optical properties across the full service temperature range (−60 °C to +200 °C). This makes it the preferred transparent elastomer for demanding applications where clarity must persist over the product lifetime.

Optical Properties and Measurement

Transparency is quantified by two parameters: light transmittance (the percentage of incident light passing through the sample) and haze (the percentage of transmitted light scattered by the material). High-quality transparent silicone grades achieve:

• Transmittance ≥90% at 3 mm thickness (per ASTM D1003 / ISO 13468)
• Haze <3% for premium optical grades
• Non-yellowing: yellowness index (YI) change <2 after 1000 hours UV aging

Transmittance decreases with increasing thickness; a 1 mm sample will transmit more light than a 6 mm sample. For lighting applications, specify the transmittance at the actual wall thickness of the component.

Applications

Medical and pharmaceutical tubing: Transparent platinum-cured silicone tubing (Shore 30A–50A) is the standard for peristaltic pump tubing, IV administration sets, and other flow-critical medical applications where the clinician or machine vision system must observe fluid flow, color, and the presence of air bubbles.

Optical encapsulation and LED diffusers: LSR and RTV-2 transparent grades encapsulate LED assemblies and optical sensors, providing weather protection without reducing light output. The refractive index of silicone (approximately 1.40–1.43) is close to glass fiber, enabling efficient light coupling.

Baby feeding bottles and nipples: Transparent silicone nipples and bottle teats allow parents to observe the infant's latch and milk flow. FDA 21 CFR and LFGB compliance is standard.

Consumer product windows and inspection ports: Transparent silicone gaskets and viewing windows in food processing equipment, industrial sensors, and consumer appliances provide a hermetic seal with an unobstructed view.

Aesthetic consumer goods: Watch bands, phone cases, and lifestyle accessories where the transparent or clear-tinted look is a design element.

Available Forms: HTV, LSR, and RTV-2

Transparent HTV: Compression-molded and extruded sheets, profiles, and tubing. Hardness Shore 20A–60A. Post-cure required for full optical clarity.

Transparent LSR: Injection-molded complex geometries in high volumes. Flash-free, clean-room processable. Hardness Shore 10A–50A. Preferred for medical tubing and baby products at volume.

Transparent RTV-2 (addition cure): Clear casting and mold-making compound. Shore 5A–40A. Near-zero shrinkage enables faithful optical geometry reproduction.

Certifications for Transparent Silicone

FDA 21 CFR 177.2600 (food and medical contact), USP Class VI (pharmaceutical and medical devices), LFGB §30/§31 (Germany/EU food contact), RoHS (no restricted substances in base polymer). For transparent grades, confirm that no UV stabilizers, optical brighteners, or processing aids have been added that could affect certification status.

Contact us to verify certification documents and request transparent silicone samples for your application.