Development and Characterization of Biocomposites Reinforced with Coconut Inner Shell: Effect on Physical, Chemical, and Dielectric Properties
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Keywords:
Biocomposite, Coconut Inner Shell, FTIR Analysis, Dielectric Constant, Bulk Density, Thermal ResistanceAbstract
In this study, biocomposites reinforced with coconut inner shell (CiS) were developed to
evaluate the effects of different filler loadings on structural, mechanical, thermal, and dielectric properties.
The CiS particles were prepared by drying and grinding the inner shell of coconuts and used as a natural
filler at varying weight fractions (0, 3.9, 7.6, and 10.1 wt.%) in a polyether polyol (PEP) matrix. Methylene
diphenyl diisocyanate (MDI) was added as a cross-linking agent to initiate polymerization and form the
biocomposite. Fourier transform infrared (FTIR) spectroscopy analysis confirmed the integration of CiS
into the polymer matrix, showing characteristic peaks associated with lignocellulosic components and
urethane linkages. The bulk density of the composites increased up to 7.6 wt.% filler loading, followed by
a slight decrease at 10.1 wt.%, likely due to particle agglomeration and pore formation. Shore A hardness
results followed a similar trend, with a peak value observed at 7.6 wt.% CiS, indicating improved rigidity
and filler-matrix interaction at optimal loading. Thermal resistance (R) initially increased with the addition
of CiS, reaching a maximum at 3.9 wt.%, and declined thereafter, suggesting that excessive filler leads to
thermal conductivity pathways and structural irregularities. Microscopy analyses showed uniform pore
distribution up to 7.6 wt.% CiS, while higher loadings negatively affected homogeneity. Dielectric constant
measurements revealed a non-linear increase from approximately 2.43 to 2.89, attributed to enhanced
polarization resulting from the CiS content and the increasing number of polar functional groups. Overall,
the incorporation of CiS as a sustainable filler improves various properties of the biocomposite, with
optimal performance observed at 7.6 wt.% loading. These findings highlight the potential of agricultural
waste-derived fillers in eco-friendly composite material development, suitable for applications requiring
enhanced mechanical strength and moderate dielectric behavior.
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