ASTM D903, Standard Test Method for Peel or Stripping Strength of Adhesive Bonds provides a standard test method for peel or stripping strength of adhesive bonds under laboratory conditions, using highly specialized equipment.6
All these test standards are designed to be performed at room temperature, generally around 22 C ± two degrees (72 F ± five degrees), with RH levels at 50 percent (± five percent). Though testing labs can replicate other conditions using additional equipment. This is important because varying temperatures and humidity levels impact adhesion performance.
Temperature and humidity effects
The temperature of ambient air and the substrate can have a dramatic effect on the adhesive performance of air barriers. The adhesive compounds used in air barrier membranes tend to perform worse at low temperatures. Products bonding well at room temperature can lose their strength as temperatures drop; RH can also affect adhesive performance. Some compounds lose their bonding properties when exposed to moist, humid conditions. These factors can impact installation, and limit when and where a particular air barrier product can be used. Whether a project is planned for November in Michigan or for July in Florida, understanding the impact of temperature and humidity on the
air barrier’s adhesive properties is important.
While air barrier manufacturers typically publish temperature ranges in their product specifications, it is important to request independent testing data to ensure these claims are validated by an objective third party. The external third party testing laboratory would have to be accredited by ASTM, ICC, or another organization. This can help ensure the right product for the anticipated site conditions and provide valuable information to defend the specification.
How substrate affects adhesion
The type of substrate and its condition affects how well the air barrier bonds to it. Therefore, adhesion testing must be performed on the planned substrate material. For example, certain cementitious materials may have chemical characteristics, such as high alkaline levels, which are not compatible with certain air barrier materials and some fluid-applied membranes.
The condition of the substrate at the time of air barrier installation is also critical. In many cases, the wall has been poured or erected well before the barrier is installed and may be dirty or dusty from construction activity. Ensuring the substrate is clean and free of contaminants is a basic but useful step to ensure proper adhesion.
Often, a building will comprise a variety of wall materials, such as concrete, oriented strand board (OSB), or other prefabricated materials. In these cases, one should select an air barrier which will bond to all these materials to reduce the number of products specified, and further reduce the risk of installing the wrong barrier on the wrong material.
