Effect of Filler Size on the Properties of Oil Palm Empty Fruit Bunch High-Load Filler Biocomposite

This work aimed to study the effect of filler size on the performance of an empty palm oil fruit bunch (OPEFB) high-load filler epoxy resin biocomposite (80 vol.% OPEFB and 20 vol.% epoxy resin). The particle sizes of OPEFBs used to prepare the biocomposites were 60, 80, 100, 120 and 140 mesh. The biocomposite samples were prepared by the press method. The physical (density, porosity, thickness swelling), mechanical, and thermal properties of the biocomposite were evaluated. A universal testing machine, thermogravimetric analysis, and scanning electron microscopy were utilized to characterize the biocomposite samples. The results show that the physical, mechanical, and thermal properties of the OPEFB epoxy resin biocomposite are significantly affected by the particle size of OPEFBs. As the particle size was reduced from 0.250 to 0.105 mm, the density improved from 0.974 to 1.101 g/cm3, the porosity decreased from 15.1 to 9.1 %, and the thickness swelling decreased from 14.2 to 7.4 %. The modulus of rupture and modulus of elasticity improved from 9.7 to 22.8 MPa and 1,667 to 2,403 MPa, respectively. Thermal analysis indicated that finer fillers enhanced thermal stability. The OPEFB biocomposite remained stable up to 300 °C. Smaller filler sizes exhibited improved biocomposite properties, which were attributed to better interfacial bonding and uniform dispersion within the matrix. The results of this study demonstrate that the performance of biocomposites can be significantly enhanced by reducing the size of the fillers. These findings indicate that filler size is crucial for high-load filler biocomposites. HIGHLIGHTS A biocomposite consisting of 80 vol.% empty palm oil fruit bunch (OPEFB) filler and 20 vol.% epoxy resin has been successfully prepared. The performance of high-load filler biocomposites is critically dependent on filler size. Reducing the OPEFB particle size significantly improves physical properties (density, porosity, thickness swelling), mechanical properties (modulus of rupture, modulus of elasticity), and thermal stability. The 140-mesh OPEFB biocomposite meets ANSI 208.1 requirements for particle board type H-1, while 80- to 140-mesh sizes meet grade M-1 requirements, indicating potential for practical applications. GRAPHICAL ABSTRACT