Page 66 - Handbook of Adhesives and Sealants

34 Chapter One

TABLE 1.10 Checklist of Considerations for the
Selection of Construction Sealants 11
Required Joint Movement
Minimum Joint Width
Required Strength
Chemical Environment
In-service Temperatures
Temperatures at Time of Application
Intensity of Sun and Weather In Service
Longevity
General Climate at Application
Materials Cost: Initial and Lifetime
Installation Cost
Other
Fungicides
Radiation Resistance
Insulating or Conductive Requirements
Color
Intrusion or Abrasion Resistance
Cure Rate
Below-Grade or Continuous Water Immersion
Accessibility of Joint
Priming
Special Cleaning Requirements
Dryness
Other Restrictions

substrates, recovery from stress, and tear resistance. Significant pro-
duction properties are: cure rate, low temperature flow characteristics,
paint-over ability, color, self-leveling properties, non-bubbling proper-
ties, and cost. Aging properties of concern include: resistance to ultra-
violet radiation; low and high temperature mechanical properties; and
resistance to hydrolysis, thermal aging, and oxidation.

1.5.2 Adhesion properties
Adhesion is an important factor in determining a sealant’s perform-
ance. The same rules of adhesion that apply to adhesives also apply
to sealants. Adhesion is primarily affected by the physio-chemical in-
teraction between the sealant material and the surface to which it is
applied. However, in certain joints where there is great movement,
strong adhesion of a sealant to a specific substrate may not be desir-
able. In these situations, the adhesive strength is stronger than the
cohesive strength of the sealant, and the sealant may tear apart when
it expands or contracts. This requires that the sealant be applied so