Wood chemical modification with lactic acid oligomers (OLA) has been reported to confer promising properties for wood outdoors applications. To better understand the lactic acid interaction with wood, chemical changes following biological degradation have been characterized with a battery of tests. Fourier transform infrared (FTIR) spectroscopy has been proved to be a valuable tool for studying fungal decay and chemical changes of degraded beech wood have been already investigated. In this study, changes in modified wood chemistry following decay by brow-rot fungus were assessed by FTIR spectroscopy. Wood specimens of beech (Fagus sylvatica L.) were modified by a thermo-chemical treatment process. Oligomer systems based on lactic acid, were impregnated in oven-dried wood and polymerised in situ by heat treatment according to a treatment process reported by Grosse et al. (2016). Treated and untreated specimens were tested according to the guidelines of EN 113 standard: after water leaching (EN84), samples were exposed to Coniophora puteana for 16 weeks. Decay was assessed through weight loss: values for treated samples were in the range of 2.69% to 3.76% for modified wood and 29.7% for native beech. The ratios of the areas of the lignin/carbohydrates FTIR peaks were determined before and after exposure. Lignin, carbohydrates and cured OLA associated bands relative intensities were used to assess wood degradation. Analyse of the degradation patterns of modified wood, in comparison with unmodified wood, shows the effect of treatment on fungal mode of action regarding the attack selectivity on modified wood components (lignin, carbohydrates and OLA).

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