Polyurethane Clear 1200 – Crystal-Clear UV-Stable PU Casting Resin for Medium-Sized Castings

Crystal-clear, UV-stable polyurethane casting resin for medium-sized castings

Polyurethane Clear 1200 is a crystal-clear two-component polyurethane casting resin from Silicones and More. You mix A and B 100 : 120 by weight and have a working time of approximately 23 minutes at 20 °C. The mixed viscosity is low (100 to 350 mPa·s), so trapped air escapes easily. You can demould after approximately 12 hours, and the cured product is colourless and clear, UV-stable and suitable for outdoor use, with a hardness of Shore D 75 to 80. No mercury is added, unlike older clear polyurethane systems.

Key benefits

• Crystal clear: colourless end product that does not yellow under UV light.
• Suitable for outdoor use: UV-stable, even with prolonged exposure.
• Low viscosity: 100 to 350 mPa·s mixed, easy to degas.
• Generous working time: approximately 23 minutes at 20 °C, easy to process by hand.
• No added mercury: safer to use than older clear polyurethanes.
• Higher heat resistance after post-curing: glass transition temperature up to 86 to 90 °C.

Typical applications

• ✓ Transparent decorative castings and art objects
• ✓ Embedding small objects
• ✓ Clear models, replicas and prototypes
• ✓ Medium-sized castings in a single pour, layer thickness 5 to 15 mm

Processing

1. Work in a dry room and make sure the material and mould are at room temperature. Polyurethane reacts with moisture, including humidity in the air. Preheating the mould to approximately 40 °C helps prevent a reaction with moisture.
2. Weigh out A and B in a ratio of 100 : 120 by weight and mix thoroughly. You have a working time of approximately 23 minutes at 20 °C (100 g).
3. Pour the mixture into the mould in a steady, thin stream and avoid trapping air.
4. Pour 5 to 15 mm per layer. For thicker castings, pour in several layers: let a layer gel, but not fully cure, before pouring the next one.
5. Demould after approximately 12 hours at 20 °C. The casting is fully cured after approximately 1 day (100 g, 20 °C).
6. The thermal and mechanical properties develop quickly. You can improve the thermal behaviour by post-curing the casting in the mould for an hour or longer at 60 °C. For even higher heat resistance, post-cure longer or at a higher temperature: the glass transition temperature is 46 to 50 °C after 7 days at room temperature, 58 to 62 °C after 3 hours at 80 °C and 86 to 90 °C after 16 hours at 100 °C.

Points of attention

• ✓ Completely bubble-free casting works best under pressure: place the filled mould in a pressure pot at approximately 4 bar during the gel time.
• ✓ Preferably use a mould made of platinum (addition) silicone. If you use a new mould made of condensation silicone, post-cure it first for 1 to 2 hours at 100 to 140 °C and let it cool. This prevents a tacky surface.
• ✓ Clear 1200 is easy to process by hand. For professional use and large castings, we recommend machine processing.
• ✓ The working, demoulding and curing times given apply to 100 g at 20 °C and a thickness of 0.5 to 1.5 cm. Low temperatures extend these times.
• ✓ Always use the materials at room temperature.
• ✓ Crystallisation of component B can be resolved by slowly warming it to approximately 60 °C for a few hours and then letting it cool back to room temperature.
• ✓ Store both components dry between 18 and 28 °C in tightly closed packaging. They will then keep for approximately 6 months. Use opened packaging as soon as possible.

Professional support

Not sure whether Clear 1200 suits your casting, or which mould works best? Email us at info@siliconesandmore.com and we will be happy to help.

Documentation

• Product information sheet Polyurethane Clear 1200 (Dutch)
• Manual: casting with Polyurethane Clear 1200 (Dutch)
• Safety data sheet component A
• Safety data sheet component B