Wall Gunnable Sealants, What are wall gunnable sealants

Wall gunnable sealants speaks to what are wall gunnable sealants, why use wall gunnable sealants, types of wall gunnable sealants.

These are materials that are viscous, sticky liquids that are injected into the joints of a building with a sealant gun. They cure within the joint to become rubberlike materials that adhere to the surrounding surfaces and seal the joint against the passage of air and water.

Gunnable sealants can be grouped conveniently in three categories according to the amount of change in joint size that each can withstand safely after curing.

Low range sealants also called caulks are materials with very limited elongation defined as stretching and squeezing capabilities, up to plus or minus 5 percent of the width of the joint. They are used mainly for filling minor cracks or non-moving joints, especially in preparation for painting.

Most caulks cure by evaporation of water or an organic solvent and shrink substantially as they do so. None are used for sealing of joints in building exterior wall systems. The term caulk is properly applied only to low range sealants, in common usage it is frequently applied more broadly to mean any type of sealant, regardless of elongation capability.

Medium range sealants are materials such as butyl rubber or acrylic that have safe elongations in the plus or minus 5 to 10 percent range. They are used in the building exterior wall for sealing nonworking joints, which are joints that are fastened together mechanically as well as being filled with sealant.

Because these sealants cure by the evaporation of water or an organic solvent, they undergo some shrinkage during curing.

High range sealants can safely sustain elongations up to plus or minus 50 to 100 percent. They include various polysulfides, which are usually site mixed from two components to effect a chemical cure. Polyurethanes which may also cure by a two component action or by reacting with moisture vapour from the air, depending on the formulation and silicones which all cure by reacting with moisture vapour from the air.

None of these sealants shrink upon curing because none relies on the evaporation of water or a solvent to affect a cure. All adhere tenaciously to the sides of properly prepared joints. All are highly resilient rubberlike materials that return to their original size and shape after being compressed and all are durable for 20 years or more if properly formulated and installed.

Sealants for the working joints in exterior wall systems are selected from among this group. Polysulfide sealants have the longest history of use in such applications. However, improved formulations of of polyurethanes and silicones now account for more than 90 percent or more of the high range construction sealant market, with silicones generally considered the longest lasting and highest performing of the three.  

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