Nonsag sealant

Control of Thixotropy. Often the adhesive application will require that the product be fluid for mixing and application, but it must not flow or sag once applied. For example, ASTM C920 defines a nonsag sealant as one that permits application in joints on vertical surfaces without sagging or slumping. This property is called thixotropy. Thixotropic materials, such as tomato catsup, toothpaste, etc., undergo a decrease in viscosity when subject to shearing. 

Heat-Softened, Nonsag Sealants. These sealants and caulks require heating to be properly dispensed and applied. They may be heated in ovens, heat chests, or boiling water to the manufacturer s recommended temperatures. For proper application and performance, care must be taken not to overheat them prior to application, nor to apply below the manufacturer s minimum temperature recommendations. 

Other Thixotropic Additives. Microcellular fillers such as glass and plastic are also used to provide nonsag properties to adhesives and sealants. However, their mode of operation is very much different from that of the rheological modifiers mentioned above. Microcellular fillers work because they drastically reduce the specific gravity of the product. Thus, because the adhesive or sealant is lighter, there is less stress on the adhesive or sealant due to the forces of gravity. 

Butadiene, 2-methyl-, polymer with 2-methyl-1-propene Butyl rubber Isobutylene/isoprene co-polymer Kalar 5214 Kalat 5263 Kalene 800 2-Methyl-1,3butadiene polymer with 2-methyl-1-propene Poly(isobutylene-co-isoprene). Cross-linked butyl composition produces nonsagging butyl-based sealants, e.g., automotive windshield tape, hot melt sealant as base for butyl mastics Viscosity (Mooney, ML 1- 8,100°) = 42-52. Hardman. 

Uses Commercial building sealant for crack repair, cove bead expansion Joint sealant Features Nonsag... 

Nonsag, Noncured Sealants. These noncuring materials are sufficiently thixotropic to be applied in vertical joints without appreciable sag or weep. They are applied with a knife or caulking cartridge into the joint and forced against the sides of the substrates. They may require warming to be applied properly. 

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