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3.3.11 Creep-Rupture Performance of Adhesively-Bonded Roofing Seams

Mark G. Vangel

Statistical Engineering Division, ITL

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 measures of performance for the experimental seams are strength and creep lifetime, i.e. the time-to-failure under a constant load. In Phase 1 of this investigation, specimens from two tape systems and a liquid adhesive were tested in creep-rupture at various loads. The main conclusion of this phase was that the tape-bonded seams appear to perform at least as well (in terms of creep life) as adhesive-bonded seams. In Phase 2, the influence of application factors on performance was investigated.

Phase 3 of this study consists of five experiments, investigating the following:


Effects of elevated temperature during loading,

Effects of elevated temperature exposure during fabrication,

Effects of exposure to industry-developed protocols,

Effect of cold temperature during fabrication, and

Seam response in shear.
The responses measured included strength and creep life.

The figure displays the strength data from the second experiment, during which roof seam specimens were prepared at various elevated temperatures, and left at these temperatures for varying times. There are several interesting patterns in these data, the most obvious of which is that both tape adhesive systems appear to be stronger than the liquid adhesive system.


Figure 23: Strength as a function of elevated temperature and time at temperature of tape (TS1, TS2) and liquid (LA) adhesively-bonded EPDM seams. Open circles identify room-temperature control tests.

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Date created: 7/20/2001
Last updated: 7/20/2001
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