Characterizing acrylic foam pressure sensitive adhesive tapes for structural glazing applications—Part I: DMA and ramp-to-fail results

The objective of this study was to determine relevant, primary mechanical characteristics of high-performance acrylic foam pressure sensitive adhesive (PSA) tapes, an alternate fastening method for structural glazing applications. Traditional fastening methods for structural glazing typically employ structural silicones and, consequently, relevant ASTM test standards and specifications appear to be more appropriate for silicones and similar products that exhibit limited time dependence. This study was aimed at characterizing and evaluating acrylic foam PSA tapes for structural glazing applications, and because of their time dependence, viscoelastic characterization was included. Since there may be significant differences in the viscoelastic responses of acrylic foam PSA tapes and silicones, the study may account for important differences between acrylics and silicones in structural glazing applications. The acrylic foam PSA used in the study was 3M™ VHB™ Tape G23F. For comparison, parallel ramp-to-fail tests were also conducted on 3 silicones: two one-part and one two-part compositions. Mechanical characteristics determined for the VHB™ Tape included the viscoelastic properties over a range of temperatures and test rates. Mechanical characteristics available in the literature were assumed for the silicones and confirm their limited time dependence. Ramp-to-fail strength data (Part I paper) and creep rupture (accompanying paper, Part II paper) data was collected for the VHB™ Tape and the silicones. Using the time–temperature superposition principle, master curves of VHB™ Tape storage and loss moduli in shear and tension were developed with data from a dynamic mechanical analyzer (DMA). The thermal shift factors obtained from these constitutive tests were successfully applied to the VHB™ Tape creep rupture and ramp-to-fail data collected at 23, 40, and 60 °C, resulting in master curves of ramp-to-fail strength (in Part I of paper) and creep rupture durability (Part II paper) in shear and tension.