Transport Mechanisms of Small Molecules through Polyamide 12/Montmorillonite Nanocomposites

Abstract

The aim of this work is to study the transport of small molecules through the hybrid systems polyamide 12 (PA12)/organo-modified montmorillonite (Cloisite 30B, C30B) prepared by melt blending, using two blending conditions. The transport mechanisms were investigated by using three probe molecules: nitrogen, water, and toluene. While a barrier effect appears clearly with nitrogen, this effect changes with the amount of fillers for water and disappears for toluene. The reduction of permeability for nitrogen is mainly due to the increase of tortuosity. For water and toluene, the permeation kinetics reveals many concomitant phenomena responsible for the permeation behavior. Despite the tortuosity effect, the toluene permeability of nanocomposites increases with C30B fraction. The water and toluene molecules interact differently with fillers according to their hydrophilic/hydrophobic character. Moreover, the plasticization effect of water and toluene in the matrix, involving a concentration-dependent diffusion coefficient, is correctly described by the law D = D(0)e(gammaC). On the basis of Nielsen's tortuosity concept, we suggest a new approach for relative permeability modeling, not only based on the geometrical parameters (aspect ratio, orientation, recovery) but also including phenomenological parameters deduced from structural characterization and permeation kinetics.

Water transport properties of bio-nanocomposites reinforced by Luffa cylindrica cellulose nanocrystals

“…4). In most cases, the reduction of permeability due to the nanoparticle incorporation is relative to a decrease in diffusion of small molecules [11][12][13]. Surprisingly, in the present work, an increase in water diffusion coefficient is exhibited as a function of nanowhisker content (Fig.…”

“…It is a general observation that the diffusion pathway is increased by tortuosity effect generating a barrier effect in polymer film which causes a change in the diffusion of small molecules and, hence, in the permeability [8,[11][12][13]. To date, and according to our current knowledge, few works dedicated to transport properties against water, organic solvents, gases for cellulose nanowhisker reinforced biobased materials are reported [2,14,[15][16][17][18][19][20][21], considering the rising interest in both academia and industry since 15 years.…”

Reinforcement of the Gas Barrier Properties of Polyethylene and Polyamide Through the Nanocomposite Approach: Key Factors and Limitations

“…A lot of attention has been particularly paid these last years on nanofillers such as clays to reinforce PA or PE properties [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. Indeed due to their high aspect ratio and their impermeable character, the clay platelets are expected to induce significant tortuosity effects when they are dispersed within a polymer matrix.…”

“…Hence much attention has been paid to obtain such morphologies, characterized by a high degree of clay exfoliation. However, the simple tortuous path model which considers the nanocomposite as an ideal binary system can not explain some experimental observations in the literature that yield either much lower [43][44][45] or on the contrary much higher permeability values than predicted [22,[28][29][30]. New conceptual approaches consisting in considering heterogeneous materials as resulting from three phases, namely the continuous phase, the dispersed phase and the interface, have progressively come to light [22,28,30,[43][44][45][46][47].…”

Characterization of Polymer Layered Silicate Nanocomposites by Rheology and Permeability Methods: Impact of the Interface Quality

“…Especially in polyolefines, a decrease of the barrier properties is sometimes reported [68,[88][89][90]. Hence, the relative barrier properties have been found to depend either on the permeant molecules [39,91], or the cationic exchange [92,93], or the clay concentration in an unexpected way [68,91,94,95].…”