New method for the synthesis of formaldehyde-free phenolic resins from lignin-based aldehyde precursors

•The synthesis of resol-type phenolic resins without formaldehyde is presented.•The functionalization of bio-based phenolic compounds into aldehyde was investigated.•Model reaction in the presence of phenol was carried out.•The thermo-stability of the obtained bio-based phenolic resins was established.

Phenolic resins are mainly obtained from phenol and the highly toxic and volatile formaldehyde. In order to synthesize new formaldehyde substituents for the synthesis of resol-type phenolic resins, we designed a method to functionalize phenolic compounds with aliphatic aldehydes by a two-steps reaction: the functionalization of an acetal group on aromatic hydroxyl functions and the subsequent deprotection of theses acetal groups into aliphatic aldehyde groups. This method was used on the lignin-based aromatic aldehyde precursors i.e. 4-hydroxybenzaldehyde and vanillin to turn them into reactive and difunctional biobased aromatic aldehyde precursors. Those precursors proved to lead to formaldehyde-free and biobased phenolic resins with competitive thermal properties compared to the usual formaldehyde resins.

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