Cold Process Adhesives
Cold applied adhesives have been used in roofing applications for over 50 years. They have become increasingly popular as an alternative to hot-applied adhesives in areas of difficult access, in odour sensitive environments or as an alternative to mechanically fastening building elements such as sub-deck materials or insulation.
These adhesives are used in adhering roofing components including ply sheets used in the assembly of a roofing membrane, insulation panels or other elements to different deck types.
Cold-applied adhesives were originally a simple bitumen cut-back, where bitumen was dissolved in solvent. They have since evolved to include emulsion or water-based technologies and more recently, solvent-free, polymer based one-component or two- component technologies. Each type is generally composed as follows:
- Solvent-based adhesives may contain some or all of the following ingredients: asphalt, solvent, reinforcing fibres, fillers, thickeners and polymer.
- Emulsion or water-based adhesives or coatings may contain some or all of the following ingredients: asphalt, clay, reinforcing fibres, fillers, thickeners and latex. These types of adhesives are primarily used as a smooth surfacing finish and not generally used to adhere the felts.
- Moisture-cured single component is a polyurethane based adhesive that is cured by moisture from the air and may also involve a solvent release. May contain some or most of the following ingredients: asphalt, solvent, reinforcing fibres, fillers, flexible polymers, accelerators and foaming agents.
- Two-component adhesives cure with the addition of a curing agent. Some of these adhesives cure to a rubbery consistency while others are dispensed through specialized equipment and cure to a low-rise foam. May contain some or most of the following ingredients: asphalt, solvent, reinforcing fibres, fillers, flexible polymers, accelerators and foaming agents.
Cold-applied adhesives are formulated and designed for specific end uses such as function, exposure, material compatibility and/or desired rate of cure.
Cold-applied adhesives are also characterized by their ability to be applied at ambient temperatures, without the need for heating. Although primarily applied at temperatures above 4.4ºC (40ºF), applications below this temperature may be acceptable following the specific cold weather guidelines set out by the adhesive manufacturer.
Depending on the type of cold-applied adhesive, the adhesive is applied by brush, squeegee, roller, spray and other dispensing pieces of equipment. Equipment for spraying can incorporate either pneumatic equipment or hydraulic spray equipment (with in-line heaters). Spraying is fast and uniform and is the preferred method of applying the cold adhesive. Ensure that any adjacent building components are not affected by potential overspray, particularly on windy days.
The cure rate of cold-applied adhesives can vary from hours to weeks according to their designed formulation and curing mechanism, application (type, coverage rate) and ambient weather conditions (temperature and humidity). Unlike hot-applied adhesives that are applied hot and cure on cooling to ambient temperatures, (which can vary from minutes to a couple of hours depending upon ambient temperature).
Cold Process Felts
Unlike felts used for hot-applied roofing which are porous, asphalt saturated but not coated, the felts used in cold process roofing are heavier and asphalt coated. These felts not only provide strength but the asphalt coating provides waterproofing.
Cold process felts can be reinforced with glass, polyester or a combination of both. Although some coated felts can be installed without cutting into shorter lengths, approximately 4.5 m to 5.5 m (15 ft to 18 ft), many cold process felts require pre-cutting and relaxing prior to installation to avoid buckling or ridging after installation.
The cold-applied adhesive, although contributing to the over-all waterproofing of the membrane, the primary function is to bond the coated felts together.