By making react mixtures containing acetic-fatty anhydrides on Scots pine sawdust (SPS) without any solvent or catalyst; we synthesized mixed acetic-fatty esters of SPS. Such mixtures were synthesized by reaction between a carboxylic acid and acetic anhydride. These mixtures were obtained after reaction of acetic anhydride and a fatty acid that yields at equilibrium a mixture of five compounds: acetic-fatty anhydride, acetic anhydride, fatty acid, acetic acid and fatty anhydride. The influence of treatment conditions, temperature, molar ratio, reaction time, and length of the fatty chain on the esterification and on the ratio of grafted acetyl/fatty acyl was investigated. Measurement over 5 minutes of static contact angles (CA) with water permitted to evaluate the water repellency of esterified SPS. CA-values were dependent on the fatty acyl content and independent of the acetyl content. The minimum ester content of the oleoyl group required to obtain permanent water repellency (WR) was 25 mmol.Kg-1. Water vapor adsorption measurements indicated that contrarily to WR, hydrophobicity to water vapor was correlated to the total mass acyl content.

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