ABSTRACT
The rates and amplitudes of movements from actual building joints were translated to a novel laboratory-based rig. This rig was used to cycle a variety of tensile adhesion joints made with and without backer rod. The key properties of “25% modulus” and “extension at peak load” were used as the mechanical performance indicators, whilst DMTA measurements were undertaken on bulk sealant samples to monitor the development of cure. In general the one-part sealant systems were affected far more by movement during cure than the two-part products. DMTA measurements indicated that the effect of movement was to actually increase the rate of cure of the one-part systems. However, the overall joint performance was reduced because of voiding and deformation of the sealant bead, as well as a loss of adhesion (which was made worse by the presence of a backer rod). The reductions in modulus and extension were broadly in proportion to the rates and magnitudes of imposed movement.
It is suggested that the test procedure represents a rapid method of screening candidate sealant systems (sealant/primer/backer rod) which are being evaluated for applications in joints in curtain walling.
