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CHT Q-Sil 553 Grey Thermally Conductive Potting Compound

Silmid P/N: VAR0000533
From £36.85 (excl VAT) £44.22 (Inc VAT)
CHT QSil 553 is a thermally conductive potting compound, specially designed for electronic potting applications.

Product Properties


Product Information

This is a 2-component, silicone elastomer system specially designed for electronic potting and encapsulation applications. It offers good protection against chemicals, environmental contamination, mechanical shock, vibration and impact damage. It can be employed in areas where low flammability is a prerequisite. The cured elastomer can be repaired. The component parts have relatively low viscosities and are readily mixed either by hand or machine.


  • Thermally Conductive
  • 1:1 Mix ratio
  • Moderately
  • Low Viscosity Low Modulus

Use and Cure Information:

IMPORTANT: The 'A' part of the product contains the platinum catalyst, great care should be taken when using automatic dispensing equipment. Please ensure that it is not contaminated by residual hydride containing rubber in the dispensing equipment, as curing will result. If in doubt, its advised to thoroughly purge the equipment with a suitable hydrocarbon solvent or silicone fluid.

Mixing: Both the A and B parts should be well stirred to ensure the material is uniform and any settled the fillers have been remixed. Place the required amount of A and B parts by weight at the mix ratio shown opposite, in a clean plastic or metal container of approximately 3 times their volume, and mix until the colour of the mixture is uniform. For best results, we recommend degassing. Degas by intermittent evacuation, the larger volume of the mixing vessel helps prevent overflow during this operation. In the case of automatic dispensing with static mixing head, the two components should be degassed before processing. Recommended vacuum conditions are 30-50 mbar intermittently over 5-10 minutes. Cast the mixture either by gravity or pressure injection.

Inhibition of Cure: Great care must be taken when handling and mixing all addition cured silicone elastomer systems, ensuring that all the mixing tools (vessels and spatulas) are clean and constructed in materials which do not interfere with the curing mechanism. The cure of the rubber can be inhibited by the presence of compounds of nitrogen, sulphur, phosphorus and arsenic; organotin catalysts and PVC stabilizers; epoxy resin catalysts and even contact with materials containing certain of these substances e.g. moulding clays, sulphur vulcanised rubbers, condensation cure silicone rubbers, onion and garlic.

Technical Information:

Uncured product:

  • Appearance Viscous Liquid
  • Colour A Part Beige
  • Colour B Part Black
  • Cure Type Addition
  • Max Cure Hrs @ 25 °C 24 hrs
  • Max Cure Mins @ 100 °C 7 mins
  • Mix Ratio 1:1
  • Pot Life mins 100 mins
  • Rheology Liquid
  • SG A Part BS ISO 2781 1.63
  • SG B Part BS ISO 2781 1.63
  • Self Bonding No
  • Viscosity A-Part mPas Brookfield 6000 mPas
  • Viscosity B-Part mPas Brookfield 6000 mPas
  • Viscosity Mixed mPas Brookfield 6000 mPas
Cured product:
  • After 15 minutes at 150°C
  • CTE Linear ppm/°C 217 ppm/°C
  • CTE Volumetric ppm/°C 650 ppm/°C
  • Colour Grey
  • Duro Shore A ASTM D 2240-95 45
  • Elongation % ISO 37 240 %
  • Max Working Temp +°C AFS_1540B 260 °C


  • CHT Q-Sil 553 2-Part Thermally Conductive Potting Compound Grey A/B Kit
  • Available in various sizes
  • Shipping information

    Orders over £100 placed online will now qualify for FREE UK Mainland delivery*

    Orders under £100 placed online for UK Mainland delivery is £12.00*

    **Orders requiring Pre 10.00am Next Day delivery has also been lowered from £35.00 to £30.00, orders placed through the office will incur additional charges.** 

    International delivery (door to door delivery) is available for selected countries worldwide. Shipping will be automatically calculated based on the weight, location and hazardous nature of the goods. Customers can also choose ex works to arrange their own collection.

    Please refer to our delivery page for more information.