February 18, 2020

Silicone Sealants vs. Urethane Sealants, What's Best for Your Building?

Often times while working with architects and contractors, we receive questions regarding the differences between urethane-based and silicone-based sealants. Other than chemistry, the simplest difference is the warranties.

A silicone-based sealant carries a longer-term warranty ranging from 10 to 20 years, as opposed to the standard 5-year urethane warranty which is common in the industry. By choosing silicones with longer-term warranties, the life cycle coat of sealing your building could be greatly reduced. Would you rather seal your building two to three times over a twenty-year period? Or just once? Both chemistries are capable of sealing your building and providing the waterproofing desired, but the decision basically comes down to warranty period and what makes sense for the life cycle cost for your particular building.

The more involved answer would touch on the differences between adhesion properties, application and appearance, base polymer properties with respect to weatherability, and manufacturer customer service.

  • Adhesion Properties: Adhesion properties are mostly determined by specific formula differences among manufacturers and generalizations cannot be made across sealant chemistries. It’s best to do the work up front on large projects utilizing the testing services supplied at no charge by most reputable sealant manufacturers.
  • Application and Appearance: Application, handling characteristics, appearance, and color availability are determined more by individual formulation variations and will need to be assessed by the applicator as to preference and suitability.
  • Base Polymer Properties: The base polymer used in silicone sealant compounding is poly-di-methylsiloxane which is inherently stable when exposed to UV light – meaning is will not degrade or deteriorate. It is said that the silicone polymer is inorganic because it has no organic components that deteriorate when exposed to typical weathering conditions. The inorganic portion is comprised of silica atoms, or more commonly known as the mineral, sand. Silicone polymers do in fact contain carbon atoms thereby excluding them from the purely inorganic family of materials.

The most significant difference of a silicone-based polymer when compared to a urethane polymer is the Si-O (silica-oxygen) bond as opposed to the C-O (carbon-oxygen) bond found in urethane sealants. The Si-O bond is much more UV stable then the C-O bond, hence the better inherent weatherability of the silicone-based sealant regardless of formula variation. The less UV stable C-O bond can be improved upon through the addition of UV protectors, anti-oxidants, UV absorbers, etc. The weatherability of the urethane-based material is more determined by the formula difference among manufacturers as opposed to the base polymer used.  

  • Consider This: The most critical factor when working with any product are the services provided by the manufacturer. Do they provide extensive testing, real-person customer service, on-site training, technical services, or supply immeasurable resources?

In the end, the choice between silicone and urethane will invariably come down to one of cost and warranty period when factoring out personal preference and formula specific differences. However, don’t overlook perhaps the most important factor to consider when choosing the proper sealant for the job: the services provided by the sealant manufacturer may ultimately have much more to do with your success than your choice of sealant chemistry.


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