Polymeric adhesives such as acrylics and epoxies are commonly used for the reconstruction and repair of ceramic and glass artifacts. Currently used epoxies have superior strength but are non-reversible after they have cured, making any important structural artifact corrections impossible. Thermally reversible epoxies with Diels Alder cycloadduct weak links have been previously reported but generally utilize solid epoxy precursors. In this work we have prepared a liquid bis-epoxy precursor with two maleimide-furan cycloadducts in the bridging group. The cycloadducts, while unaffected by the epoxy curing reactions, undergo a retro [4 + 2] cycloaddition when heated above 90 °C that results in the liquefaction of the resin. At this point, the resin can be removed from the artifact or allowed to reform the cycloadduct bonds to reform the thermoset. Adhesive bond strength of the new adhesive was determined using lap shear testing. The reworkability of the resin was determined by heat treating lap shear samples until the thermoset was liquefied, then resetting and cooling the sample to reform the bond. We found that the thermally reversible adhesive could be reworked four or five times before the adhesive strength degraded. Through such tests we were able to show that these adhesives can be easily re-worked and act as a useful new tool for object conservation.

Thermally re-workable epoxy adhesives for use in artifact repair

251st National Meeting (2016)

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