SEMICOSIL® 821 UV is a non-slump silicone adhesive that is cured by UV conditions with unique cure behavior for automotives.

This is specially designated for the combination process of screwing and UV curable gluing and oven-free processing or wet bonding during processing with fast adhesion built-up at oven processing.


Special characteristics

  • Long and controllable liquid retention time after UV
  • Primerless adhesion to many substrates
  • Liquid or gel state during processing after UV exposure
  • Fast curing and adhesion built-up at the minimum energy input
  • Thixotropic for non-slump
  • Long pot-life of the A+B mixed

Specific features of SEMICOSIL® 821 UV A

  • Addition Curing
  • Non-slump
  • Two-component
  • UV curing
  • Assembly glue for displays
  • Bonding material or sealing agent in electronics, automotive and other industrial applications


Surface preparation

All surfaces must be clean and free of contaminants that will inhibit the cure of SEMICOSIL® 821 UV A and ELASTOSIL® Cat UV.

Examples of inhibiting contaminants are sulfur-containing materials, plasticizers, urethanes, amine-containing materials, and organometallic compounds – especially organotin compounds. If a substrate’s ability to inhibit cure is unknown, a small-scale test should be run to determine compatibility.


Mixing ratio

Part A (SEMICOSIL® 821 UV A) : Part B (Elastosil® Cat UV) =  10 : 1



Curing speed can be adjusted by UV irradiation and time. Also, heat can accelerate the curing process.

We recommend running preliminary tests to optimize conditions for the particular application. Comprehensive processing instructions are given in below; 

  • Recommended Lamp Type: UV-A, Mercury, 365 nm LED
  • For Normal process, Metal Halid is recommended 
  • For Hybrid process (UV first, then laminate); UV energy should be controlled depending on the open time from UV activation to Lamination

If the applied lamp is 365nm LED lamp, the higher UV irradiance would be better (ex. 2,000 mW/cm2).

Tack-free time can be increased or decreased depending on the applied irradiance of the energy source.





SEMICOSIL® 821 UV A and ELASTOSIL® Cat UV should be stored between 5 °C and 30 °C and below 60%RH in the tightly closed original container.

The 'Best use before end' date of each batch appears on the product label.

Storage beyond the date specified on the label does not necessarily mean that the product is no longer usable. In this case, however, the properties required for the intended use must be checked for quality assurance reasons.

Sales and support

Wacker Chemical Corporation
3301 Sutton Road
Adrian, MI 49221-9397
United States
+1  888  922-5374 (Phone)

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