Comparative study of two biocomposites: Effect of date stone flour treated with potassium permanganate as a filler on the morphological and elastic properties

The paper deals with the effect of date stone flour (DSF) as a filler on the elastic properties of biocomposites based on two different matrices, namely, polymethyl methacrylate (PMMA) and green epoxy resin (GER). Potassium permanganate treatment was applied to improve the surface properties of the DSF filler. Fourier transform infrared spectrotroscopy was used to analyze the chemical changes of the functional groups in the untreated DSF and the permanganate treated DSF filler. Different filler content of 10, 20, and 30 wt%, respectively, were used to obtain PMMA/DSF and GER/DSF biocomposites. The elastic properties, namely, longitudinal modulus, shear modulus, bulk modulus, Young's modulus of elasticity, Poisson ratio, ultrasonic micro-hardness, and acoustic impedance of the biocomposites were determined using the ultrasonic through-transmission method. In addition, the morphology was studied using optical microscopy and scanning electron microscopy. Fourier transform infrared spectrotroscopy analysis results revealed the success of the permanganate treatment. The elastic properties of PMMA/DSF biocomposites were decreased, while an improvement of these properties is observed for GER/DSF biocomposites. Morphological results showed the presence of pores and cracks in the PMMA/DSF biocomposites, which is attributed to poor interfacial adhesion between the DSF filler and the PMMA matrix. However, fewer defects were observed in the GER/DSF biocomposites, which is due to better interfacial adhesion between the DSF filler and the GER matrix.