Green epoxy resin/date stone flour biocomposites: Effect of filler chemical treatments on elastic properties

Abstract This work aims to study the effect of chemical treatments of date stone flour (DSF) as a filler on the elastic properties of biocomposites based on green epoxy resin (GER) used as a matrix. The main disadvantages of natural reinforcements in biocomposites are the poor compatibility between the reinforcement and the matrix as well as the relatively high moisture sorption. Different chemical treatments using soda (alkaline), benzoyl chloride, and potassium permanganate were applied to the DSF filler. Then, the filler was incorporated into the matrix at 30 wt% to obtain GER/DSF biocomposites. The elastic properties of the biocomposites, namely, longitudinal modulus, shear modulus, bulk modulus, Young's modulus of elasticity, acoustic impedance, Poisson's ratio, and ultrasonic microhardness, were determined using ultrasonic through‐transmission method. In addition, the morphology was studied using microscopy analysis. The results obtained revealed a decrease of the elastic properties of the pretreated‐filler biocomposite compared to the pure GER. On the other hand, the chemical treatment of the filler leads to an improvement of the elastic properties of GER/DSF biocomposites. The permanganate treatment is the most suitable for GER/DSF biocomposites. The morphology analysis through optical microscopy and scanning electron microscopy showed that chemical treatments enhance the interfacial adhesion between the DSF filler and the GER matrix.