Study of the Moisture Absorption in Polymer Composites Reinforced with Vegetal Fiber Using Langmuir’s Model

Abstract

This work aims to numerically study the moisture absorption in polymer composites reinforced with vegetal fiber, using the diffusive model of Langmuir, which considers the existence of water molecules inside the material free to diffuse and adsorb at the capillaries walls, in the solid. A threedimensional and transient mathematical modelling to describe the water absorption process by the composite and its numerical solution via finite volume method are presented and discussed. Results of the free solute concentration, entrapped solute concentration, local moisture content and average moisture content obtained at different instants of the process are presented and analyzed. It was verified that the concentration gradients of the molecules (free and entrapped) are higher at the material surface. In addition, as the concentration of free water increases, there is also an increase in entrapped water concentration within the material at any time of the process.

Evaluation of the Behavior of Two CAD/CAM Fiber-Reinforced Composite Dental Materials by Immersion Tests

“…Water absorption and dimensional change of CAD/CAM polymers may be affected by variations in the composition aiming to improve the mechanical properties of these polymers. This phenomenon happens due to the fluid absorption in the polymer matrix, the highest moisture absorption generally occurring within the first few days, following a tendency to stabilize [ 47 , 48 ].…”

Non-Fickian Moisture Absorption in Vegetable Fiber Reinforced Polymer Composites: The Effect of the Mass Diffusivity

“…The simulated results agreed well with experimental data and showed that the diffusion and swelling behaviors were perfectly simulated in the selected conditions. Santos et al [ 22 ] theoretically studied the water sorption process in vegetable-fiber-reinforced polymer composites using Langmuir’s model in a three-dimensional and transient approach based on the finite-volume method. The obtained results for the free and entrapped molecules concentration and local and average moisture content at different process times were presented and analyzed.…”

“…It is important to state that, in many works related to Langmuir’s model, the authors considered constant mass diffusivity [ 22 , 23 , 24 , 25 , 26 ]. However, this assumption is not completely consistent with the real process behavior, since the moisture migration rates are higher at the shorter process times and decrease for longer times; therefore, mass diffusivity varies with the water concentration inside the material [ 27 ].…”