3D Modelling of Mass Transfer into Bio-Composite

Area of Science:

• Materials Science
• Polymer Science
• Computational Modeling

Background:

• Composite materials are increasingly used, but their water vapor permeability is critical for applications.
• Poly(3-HydroxyButyrate-co-3-HydroxyValerate) (PHBV) is a biodegradable polymer matrix.
• Wheat Straw Fiber (WSF) is a natural filler, but its effect on PHBV permeability needs detailed study.

Purpose of the Study:

• To develop and validate a 3D model for predicting water vapor permeability in PHBV/WSF composites.
• To investigate the role of an interphase layer on permeability, especially at high filler content.
• To understand the influence of filler volume fraction on composite permeability.

Main Methods:

• Development of a 3D model incorporating an interphase layer around permeable inclusions.
• Generation of approximately 500 two-phase and three-phase structures using experimental WSF size distribution.
• Application of the Finite Element Method (FEM) to calculate relative permeability (P/Pm).

Main Results:

• The two-phase model accurately predicted permeability for WSF volume fractions below 11.4%.
• The two-phase model failed to capture the significant increase in experimental permeability at higher WSF content.
• The three-phase model, including a 5 µm interphase with diffusivity ≥1×10-10 m2·s-1, successfully explained the observed permeability upturn.

Conclusions:

• The interphase layer plays a crucial role in water vapor transport in PHBV/WSF composites at high filler loadings.
• A three-phase model is necessary for accurate permeability prediction in such systems.
• The developed model provides a valuable tool for designing composites with tailored barrier properties.