Novel biodegradable composites based on treated lignocellulosic waste flour as filler. Part I. Surface chemical modification and characterization of waste flour

The chemical modification of lignocellulosic materials based on waste flour, using catalyst and solvent-free reactions with acetic and propionic anhydride, was studied. The reaction of esterification between the acetyl/propionyl groups and the hydroxyl groups of the flour was confirmed by Fourier transform infrared (FTIR) analysis, while its extent was assessed by titration. Thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the thermal stability, crystallinity and surface morphology of the untreated and esterified flours. The ester content of all three flours was higher for the treatment with acetic as compared to propionic anhydride. The highest extent of the esterification was achieved for the olive husk flour due to its high lignin/hemicelluloses content. The esterified flours exhibited a decreased hydrophilicity as indicated by their moisture content reduction, while their thermal stability was slightly decreased. It was also shown that the flour crystallinity decreased slightly as a result of esterification.