Moisture Absorption in Polymer Composites Reinforced with Vegetable Fiber: A Three-Dimensional Investigation via Langmuir Model

Abstract

This work aims to study numerically the moisture absorption in polymer composite reinforced with vegetable fibers using the Langmuir model which considers the existence of free and entrapped water molecules inside the material. A three-dimensional and transient modeling for describing the water absorption process inside the composite and its numerical solution via finite volume method were presented and discussed. Application has been made for polymer composites reinforced with sisal fiber. Emphasis was given to the effect of the layer thickness of fluid close to the wall of the composite in the progress of water migration. Results of the free and entrapped solute (water) concentration, local moisture content and average moisture content, at different times of process, and inside the composite were presented and analyzed. It was verified that concentration gradients of the molecules (free and entrapped) are higher in the material surface, at any time of the process, and concentration of free solute is greater than the concentration of entrapped solute. It was verified that the water layer thickness surrounding the composite strongly affects the moisture absorption rate.

Non-Fickian Moisture Transport in Vegetable-Fiber-Reinforced Polymer Composites Using a Langmuir-Type Model

“…The absorption process was simulated considering an equilibrium moisture content of Me = 0.14488 kg/kg and a total process time of approximately 2250 h, equivalent to approximately 94 days. The values for the process parameters used in the simulations were defined based on the results reported in the literature [24,25]. Table 1.…”

“…The study was applied to caroá fibers and the authors obtained a good agreement between the theoretical and experimental data for the average moisture content throughout the process. Britoetal [24] developed a three-dimensional and transient mathematical model using Langmuir's model and its numerical solution based on the finite volume method. This was used to predict the water absorption in polymeric composites reinforced with vegetable fibers.…”

Evaluation of Water Diffusion Mechanism on Mechanical Properties of Polypropylene Composites

“…The movement of water molecules inside composite materials occurs by diffusion mechanism. Fick's law is one of the models used to predict quite a number of diffusion mechanisms of polymer composites due to its simplicity [12]. Generally, under Fickian's laws, diffusion of water molecules in composites is considered by three categories of mechanisms [13] including the flow of water molecules within the microcracks of the polymer chains, transportation of water molecules through the capillary into cavities and voids created within the fiber-matrix interface [14,15], and finally the overall effect of swelling of the composites which spreads within the microvoids of the composite matrix [15].…”

Modelling of Environmental Ageing of Polymers and Polymer Composites—Modular and Multiscale Methods

“…This behaviour is known as non-Fickian diffusion. Degradation [ 13 , 50 , 51 , 67 ], molecular relaxation [ 75 , 76 ] and specific interactions between the polar sites of the host polymer and a penetrant [ 77 , 78 , 79 , 80 ] are among the main factors contributing to the anomalous water absorption.…”