Influence of Backbone Structure on Properties of Directly Polymerized Phenoxy Resins from Epichlorohydrin and Various Aromatic Dihydric Phenols Monomers

A series of phenoxy resins was directly prepared through the polymerization of each of the various aromatic dihydric phenols and epichlorohydrin. FTIR and 1H NMR spectra were recorded to characterize the structures of the resins. The GPC curves were used to determine the molecular weight distribution. In addition, the thermal properties of the resins were studied with differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The thermal stabilities of the polymers increased with the content of the benzene ring, pendant group increasing or biphe nyl groups emerging. The adhesive properties of the polymers were evaluated in terms of the lap shear strength with Fe-Fe adherends. The fracture mechanisms were determined by SEM observation and it was found that there was an important participation of cohesive fracture mechanisms. Also, it has been demonstrated that the extension of these micro-cohesive mechanisms is directly correlated with the adhesive strength. According to these results, the phenoxy resin containing biphenyl groups presented a higher adhesive strength and could improve the adhesive property of the epoxy/phenoxy system to a certain extent.