Matting and durable coating for silicone surfaces

Silopren LSR Topcoat HE is a two-component silicone coating that you apply to cured silicones to mattify the surface and give it a durable finish. Momentive developed the coating as a durable layer for printed silicone elastomers based on LSR. Mixing is done 1:1, the mixed product remains workable for three days at 20 °C, and curing takes place in a ventilated hot air oven at 100 to 180 °C. The HE addition stands for high elongation; the layer stretches with a flexible substrate.

Key benefits

• Excellent adhesion to silicones: suitable for LSR, heat-curing silicone rubbers (HTV) and room-temperature vulcanisates (RTV). The surface only needs to be dust and grease-free; no further pretreatment is necessary.
• High elongation: the layer does not tear immediately when the silicone substrate bends or stretches.
• Abrasion resistant: 100 cycles on the Norman Tool Tester at 175 g and 50 µm dry film thickness.
• Matte, colourless finish: removes the gloss from the surface without changing the colour of the underlying material.
• High reactivity: the coating crosslinks quickly as soon as the layer reaches temperature.
• Neutral odour and taste: the cured layer does not emit its own odour or taste.
• Stable and flexible at low temperatures: the layer remains flexible when the part gets cold.
• Long pot life: three days at 20 °C, so you don't have to mix per charge.

Typical applications

• ✓ Matting of glossy silicone parts
• ✓ Durable finish for printed LSR parts, such as keypads and control panels
• ✓ Protective layer on silicones that are mechanically stressed or bent
• ✓ Finishing of HTV and RTV parts that require a matte appearance
• ✓ Parts for repeated food contact, within the frameworks mentioned above

Processing

1. Stir or shake component A and component B thoroughly and separately before use.
2. Weigh A and B in a 1:1 ratio.
3. Mix for approximately 5 minutes with a suitable mixer at a moderate shear rate.
4. Ensure that the surface to be coated is dust and grease-free; no further pretreatment is necessary.
5. Apply the coating by spraying. For longer spraying sessions, use a continuous mixing device in the supply tank to keep the mixture homogeneous.
6. Cure immediately after spraying in a ventilated hot air oven at 100 to 180 °C. Ensure sufficient fresh air supply, otherwise surface disturbances may occur.
7. Clean tools and equipment with a non-polar solvent.

The datasheet does not specify a fixed curing time; this depends on the oven temperature and layer thickness. A higher temperature of the mixed product significantly shortens the processing time.

Precautions for use

• ✓ This is an addition system. Sulfur-containing clay, latex, PVC, uncured polyurethane and epoxy, cyanoacrylate, and residues of condensation silicones can inhibit curing. If in doubt, test on a sample piece first.
• ✓ Component A has a flash point of 73 °C and component B of 76 °C. Keep the coating away from open flames and hot surfaces, and ensure good ventilation during spraying.
• ✓ The product is classified as H412, harmful to aquatic life with long-lasting effects. Prevent release into the environment and dispose of residues and packaging via an authorized processor.
• ✓ Shelf life 6 months from production date, in the original sealed packaging, stored dry at a maximum of 27 °C and less than 60% relative humidity. The exact date is stated on the analysis certificate.
• ✓ Use component A and component B only together as supplied and do not interchange caps.

Professional support

If you want to know if LSR Topcoat HE adheres to your specific silicone, or if you need documentation on FDA and BfR compliance, please contact us at info@siliconesandmore.com. Please provide information about the base material, the desired layer thickness, and the oven temperature you have available, and we will determine if this is the correct coating or if the standard LSR Topcoat is a better fit.