Strength and Creep-Rupture Properties of Adhesive-Bonded EPDM Joints Stressed in Peel

摘要

The most frequently reported defect in ethylene-propylene-diene terpolymer (EPDM) single-ply roofing systems is in field-formed joints. The causes of these joint defects are largely unknown, but they tend to occur a short time after a roof is installed. The objectives of the research were (1) to determine the importance of the following material and fabrication variables in causing joint failures: adhesive thickness, cure time, mechanical load, adhesive type and surface cleanness; (2) to rank these variables as they affect the creep-rupture life and strength of butyl-adhered EPDM joints; and (3) to determine the maximum peel stress which EPDM joints can sustain over their design life. From the results, cure time and level of cleanness of the EPDM membrane have the greatest effect on joint strength; while the thickness of the adhesive and the magnitude of the mechanical load have the greatest effect on a joint's creep-rupture time-to-failure. Thus, the rankings of variables in creep-rupture and short-time strength experiments were different and this difference should have important implications in standards writing and in establishing performance requirements for EPDM roofing joints.