Investigation of Physical Adhesion in Hemp Fibre Reinforced Composites Using Contact Angle Measurements and Inverse Gas Chromatography

Abstract

This study investigates the interface between hemp fibre and thermoplastic polymer matrices such as polypropylene (PP) and poly-acrylate (Elium®). The analysis was conducted using both traditional dynamic contact angle measurements with various probe liquids and a more novel approach involving inverse gas chromatography (IGC) with multiple gaseous probes. The goal was to predict fibre–matrix compatibility based on surface chemical characterisation. Both methods showed good correlation, with the dispersive surface energy of the natural fibres ranging between 33 and 39 mJ/m², and a significant basic component contributing to the overall polar surface energy. IGC proved more effective at distinguishing between the predominantly apolar PP and the more polar poly(methyl methacrylate) (PMMA) based Elium, with the predicted thermodynamic work of adhesion notably higher for hemp–Elium interfaces compared to hemp–PP. Micromechanical testing, combined with microscopic imaging, further supported the observation of improved intermolecular adhesion between the natural fibres and the Elium matrix.