Analysis of processing parameters influencing the dielectric performance of coconut shell polymer composites / Mekha Karayil Thekkoot Babu

Faculty of Electrical & Electronics Engineering

Thesis (Master of Science) -- Universiti Malaysia Pahang - 2026

Includes bibliographical references

The rapid growth of consumer electronics has intensified the global e-waste crisis, projected to reach 74.7 million metric tons by 2030, largely due to continued reliance on non-biodegradable dielectric materials such as teflon and mica. Although natural fillers have been explored as sustainable alternatives, systematic studies on coconut shell (CS) as a dielectric bio-filler remain limited. In particular, the influence of CS morphology, chemical composition, and elemental characteristics on dielectric performance is not clearly established, and the governing role of processing parameters remains insufficiently understood. To address these gaps, this study investigates coconut shell, a carbon-rich lignocellulosic agricultural byproduct with high cellulose and fixed carbon content, offering enhanced interfacial polarization potential compared to many other bio-based fillers. The objective of this work is to develop and optimize epoxy-based dielectric composites incorporating coconut shell and to identify the dominant parameters influencing relative permittivity. A two-level factorial design (TLFD) coupled with analysis of variance (ANOVA) and regression-based statistical modeling was employed to evaluate the effects of mesh size, filler loading, stirring time, and curing method. Morphological and elemental characterization was conducted using SEM-EDS, while cellulose content was quantified to establish structure-property relationships. Dielectric properties were measured using a 40 GHz Vector Network Analyzer, and ANOVA-based contribution analysis and regression models were applied to determine factor significance and predictive capability. The results demonstrate that mesh size and filler weight percentage are the most significant parameters governing dielectric performance, while curing method exhibits a secondary but non-negligible influence. The optimized dielectric response was obtained at a filler loading of 40 wt%, a coarse particle size of 1.18 mm mesh, and under non-heating curing conditions, yielding a maximum relative permittivity of approximately 4.1. SEM-EDS analysis revealed that the composite exhibiting the highest dielectric performance possessed a maximum carbon content of 70.94 wt%, accompanied by a comparatively reduced oxygen fraction, indicating the formation of carbon-rich interfacial regions within the epoxy matrix. SEM observations further showed that coarser coconut shell particles (1.18 mm mesh) promoted improved particle dispersion and increased inter-particle spacing, which collectively enhanced interfacial polarization. As a result, carbon-rich compositions were associated with higher relative permittivity, whereas increased oxygen content led to dipole immobilization and a reduced dielectric response. Regression-based statistical analysis confirmed that particle dispersion and inter-filler spacing are critical determinants of dielectric behavior. Overall, this study establishes coconut shell as a technically viable and environmentally sustainable dielectric filler, supporting circular-economy principles by converting agricultural waste into functional materials and providing quantitatively validated processing guidelines for applications in green electronics, energy storage, and telecommunications.