Mark G. Vangel
James J. Filliben
Statistical Engineering Division, CAML
Walter J. Rossiter
Building Materials Division, BFRL
Adhesively-bonded EPDM (a rubber material) is widely used for low-slope industrial roofing. There are two main types of adhesive systems for seams on these roofs: a liquid adhesive, and several varieties of tape adhesive. Liquid adhesive is widely used, but it is volatile and relatively expensive to apply. An objective demonstration that tape adhesives are at least as reliable as the liquid will greatly increase the use of these adhesives. A consortium of NIST, professional roofing trade associations, and roofing adhesive manufacturers was formed, in part, to perform such a study.
The chosen measure of performance for the experimental seams is creep lifetime; i.e. the time-to-failure under a constant load. The figure illustrates mean lifetime as a function of load for three adhesive systems. These means are a summary of data on approximately 600 specimens, and the fitted curves are for a nonlinear model proposed by F. A. Bastenaire (ASTM STP 511, 1972) for fatigue in metals. This experiment suggests that, in terms of creep life, tape seam perform as well as adhesive seams.
The next phase of this experimental
program, which will examine the effect of
application parameters on creep
life, has been designed and the
testing is in progress.
Figure 17: Mean Creep-Rupture Lifetime of Adhesively-Bonded Seams
Date created: 7/20/2001