16 Solvent-free epoxy resins for consolidation of heavily degraded wood KEYWORDS: Epoxy resin; wood consolidation; material testing; Anobium punctatum; woodworm damage. The study aims to select and further assess solvent free and low viscosity epoxy resins for consolidating wood severely degraded by insects. Epoxy resins are rarely used as consolidant for degraded wooden objects, even though several studies have demonstrated that they can increase the mechanical properties of the consolidated wood significantly better than e.g., polyacrylates in solution. Reasons for the rare use include concerns and prejudices on high viscosity or cure temperature. Epoxy resins are also often diluted with large amounts of solvents to reduce viscosity and reactivity. This causes problems like high level of resin shrinkage upon cure or an incomplete curing process that can be mitigated by selecting a solvent-free epoxy resin system. In a first step, a number of epoxy resin ‘candidate’ systems were composed from different types of epoxy resins, amin curing agents and epoxy-based reactive diluents. In order to identify the most suitable mixture, the different epoxy systems were consequently tested against conservation relevant criteria, such as viscosity, glass transition temperature, penetration characteristics and reaction temperature within wood. In addition, increasing the strength of degraded-consolidated wood, was considered. Tests and experiments were carried out for the epoxy resins itself as well as when applied to specimens from Scots pine (Pinus sylvestris), degraded by larvae of Anobium punctatum. The epoxy resin that showed most suitable results consisted of diglycidylether of bisphenol A and F, diluted with the reactive diluents neopentylglykol diglycidylether and alkyl (C12-C14) glycidylether and using a curing agent out of polyoxypropylenediamine derivatives. It was selected for in-depth analysis and testing to assess its processing characteristics. Effects on resistance to pressure and bending, elasticity and moisture sorption and swelling of the consolidated anobium-degraded wood were also assessed. Results reveal that the selected epoxy resin possesses good processing properties and disperses well within the specimens because of low viscosity and low reactivity. Moreover, it cures reliably at room temperature without relevant shrinkage. The mechanical properties of the consolidated wood improve significantly, without undesired stiffening, even though moisture sorption and swelling increase slightly. astrid.beling[at]gmail.com
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