Characterisation of plant flours for biocomposite applications focussing on Phragmites australis properties

Composites based on lignocellulosic fillers such as wood, miscanthus or common reed have received much attention due to their low cost and positive impact. Knowledge of the physico-chemical characteristics of plant flour is essential to obtain indications of the thermal stability and humidity behaviour of the resulting biocomposite. The different methods that can be applied to plant flours to characterise them for composite applications are presented. Chemical composition, wettability and sorption curves are the most important data that can distinguish one plant filler from another. This article focuses on the Phragmites australis (P.a.), a widespread wild plant that shows interesting properties for composite applications due to its hydrophobicity. First results indicate a significant amount of solubility in P.a. and a high presence of silicon. Despite a greater quantity of hemicellulose (polysaccharide reinforcing hydrophilicity) in reed P.a. compared to wood, it shows high hydrophobic behaviour against both water vapour adsorption and wettability. Thus, the amount of hemicellulose appears not to be a sufficient criterion to justify the hydrophilic/hydrophobic behaviour of a biocomposite based on plant flour. [Display omitted] •The fraction of hemicellulose is not the only lever of a plant flour hydrophilicity.•The nature of common reed soluble could be responsible for its hydrophobic behaviour.•The high amount of Silicon in common reed could explain its hydrophobic behaviour.