Factorial analysis of lignocellulosic content influence on the permittivity of coconut-shell epoxy dielectric composites

Abstract
The development of sustainable dielectric materials is crucial for advancing next-generation electronic and energy storage systems. This study investigates the dielectric behavior of coconut-shell-based epoxy composites and evaluates the influence of processing parameters using a two-level factorial design (TLFD) coupled with two-level factorial analysis (TLFA). The effects of filler loading, particle size, and curing condition (non-heated and heated) on lignocellulosic content and the real part of permittivity (ε′) were systematically examined at 5 GHz using a vector network analyzer. At a 40 wt.% filler content, the measured lignocellulosic content reached 58.7% (Kurschner-Hanack), with permittivity values ranging from 3.74 to 4.11. Statistical analysis identified the curing condition as the most significant factor affecting ε′, followed by filler loading and particle size. The novelty of this study lies in applying TLFD and TLFA to quantitatively evaluate how lignocellulosic content influences GHz-range permittivity specifically in coconut-shell-based dielectric composites, a compositional factor that earlier coconut-shell studies have not explicitly examined. This approach demonstrates how statistical modeling, supported by ANOVA, can bridge the relationship between material composition and electromagnetic performance in GHz dielectric composites. The findings establish a systematic framework for optimizing bio-based dielectric materials and demonstrate the potential of coconut-shell-derived composites for sustainable electronic applications.