1.2 Physico-chemical properties
In-situ polymerization of lactic acid oligomers has been analysed by FTIR spectroscopy and gel permeation chromatography.
Infra-red spectroscopy attests the occurence of polymerised lactic acid into wood structure (Figure 8). Indeed, PLA characteristic peaks at 875 cm-1 and 765 cm-1 are superimposed on wood spectra, and the shift of carbonyl absorption band from 1746 to 1764 cm-1 during heating indicates a higher ester linkage content.
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After short treatment, oligomers are not durably linked to the wood structure as around 90% weight loss by chloroform extraction is noticed. No characteristic oligomer peaks is noticed in the FTIR spectra neither. After long treatment, around 50% weight loss indicates that half the amount of oligomers remained in wood, either due to physical trapping of the molecules or hydrogen bondings.
