Ring-opening metathesis polymerization (ROMP) polymers as structural adhesives and the effects of silane coupling agents on their lap shear properties

In this study, single lap shear experiments with Al2024-T3 substrates were used to evaluate poly(dicyclopentadiene) (pDCPD) for structural adhesive applications. A wide range of monomer-to-catalyst ratios (M:C = 10,000:1 to 90,000:1) and four different silane coupling agents (i.e. hexyl, hexenyl, allyl, and norbornyl trimethoxysilane) were used to understand their effects on the adhesive shear properties of pDCPD. The roles of pDCPD oxidation and the bulk polymer on adhesive properties were also investigated using paint and dynamic mechanical analysis (DMA) measurements. Collectively, the data show that the choice of silane has a significant influence on the lap shear strengths of pDCPD, while the M:C ratio has a smaller but significant influence. Differences in bulk polymer topology as measured by DMA and oxidation of the resin had insignificant effects in the absence of exposed oxygen-rich surfaces that influence catalyst activity. With shear strengths up to 21.6 +/- 0.7 MPa for dry conditions and up to 13.0 +/- 0.7 MPa for hot-wet conditions (i.e. submersion in deionized water at 60 degrees C for 2 weeks), we showed that pDCPD-based adhesives have comparable lap shear properties to a well-studied model thermoset epoxy (i.e. DGBA/D230).