In this study, high-density polyethylene (HDPE) composites reinforced with palm kernel shell (PKS) fillers of mixed particle sizes were prepared using melt-extrusion compounding. A 5-ton hydraulic hot press machine was employed to fabricate samples for tensile testing, with a focus on understanding the influence of varying filler sizes on the mechanical properties of the HDPE/PKS composite. The results demonstrated that the incorporation of larger PKS particles (PKSL) had a detrimental effect on the tensile properties, with increasing PKSL content leading to significant reductions in tensile properties. For example, at 7.5 wt% PKSL, the elastic modulus (E) decreased by approximately 18%, yield strength by 37%, ultimate tensile strength (UTS) by 24%, stress at failure by 29%, and total elongation by 62%. Similar trends were observed for composites containing 15 wt% and 22.5 wt% PKSL. Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) were employed to assess the melting temperature ranges and thermal stability of the composites, respectively. Scanning Electron Microscopy (SEM) provided insights into the failure mechanisms, revealing weak filler-matrix interfacial bonding with larger particles, resulting in debonding and ultimately compromising the tensile properties of the composite.

The dataset for both 250-micron and 1mm particle sizes of palm kernel shells (PKS) was collected through micrographic analysis. An ImageJ software was used to measure the particle lengths from micrographs of the PKS. The data collected through ImageJ was exported as CSV files for both particle sizes. the data was then imported into Excel, where  random numbers were generated based on the mean and standard deviation of the measured data. 

For the FTIR analysis, the data was obtained using an ATR-FTIR machine in the lab. The machine provided transmittance and wavenumber values for the PKS, which were then used to analyze the chemical composition of the material.