Sealants, perimeter joints

Solvent-based acrylic sealants are used for areas where there is limited movement, such as perimeter joints around doors and windows, wood sashes and wood-to-masonry joints, precast joins, panel-to-panel joints and stone cladding. The properties of solvent-based acrylic sealants are summarised in Table 5.3. 

With these tools, it has been possible to develop a whole range of silicone sealants with cure kinetics designed for many different requirements (Fig. 11). The acetoxy sealants are fast curing, and thus well adapted to glazing applications. The oxime sealants are better suited for adhesion on plastics. For applications where a longer tooling time is required, such as expansion seals or perimeter joints, Alkoxy sealants have been developed with a longer skin-over time. 

Applications of low movement sealants include perimeter joints of residential door and window frames, siding, or interior duct work. Generally, they require a minimum amount of surface preparation, have good adhesion characteristics, and are supplied in one-component cartridges. 

Curtain wall and perimeter joints - Two component polysulfide and polyurethane and one component silicone sealants are used in these appHcations because they tolerate high joint movement. This ranges up to +25% for polysulfide and from +20 to 50% for the polyurethane and silicone sealants. 

Solvent-based sealants one-component non-staining good weathering good chemical resistance perimeter pointing cladding pre-cast joints... 

Completely cured one-component polysulphide sealants are elasto-plastic and elastic in character. They have a movement accommodation factor of 20%-25%. These types of sealants are particularly suited for the perimeter sealing of window joints [Figure 7.2(a)], joints between precast concrete panels [Figure 7.2(b)], movement joints in brickwork where the movement is likely to be relatively slow, stone claddings, etc. The life expectancy for one-component sealants is, like that of two-component sealants, 20-25 years. 

Flgnre 7.2 Use of polysulphide sealant for (a) perimeter seating of window joints (b) in joints between precast concrete slabs. Cross-hatched area = one-part polysulphide sealant ... 

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