Gas barrier of polystyrene montmorillonite clay nanocomposites: Effect of mineral layer aggregation

Abstract

Three polystyrene (PS)/clay hybrid systems have been prepared via in situ polymerization of styrene in the presence of unmodified sodium montmorillonite (Na‐MMT) clay, MMT modified with zwitterionic cationic surfactant octadecyldimethyl betaine (C18DMB) and MMT modified with polymerizable cationic surfactant vinylbenzyldimethyldodecylammonium chloride (VDAC). X‐ray diffraction and TEM were used to probe mineral layer organization and to expose the morphology of these systems. The PS/Na‐MMT composite was found to exhibit a conventional composite structure consisting of unintercalated micro and nanoclay particles homogeneously dispersed in the PS matrix. The PS/C18DMB‐MMT system exhibited an intercalated layered silicate nanocomposite structure consisting of intercalated tactoids dispersed in the PS matrix. Finally, the PS/VDAC‐MMT system exhibited features of both intercalated and exfoliated nanocomposites. Systematic statistical analysis of aggregate orientation, characteristic width, length, aspect ratio, and number of layers using multiple TEM micrographs enabled the development of representative morphological models for each of the nanocomposite structures. Oxygen barrier properties of all three PS/clay hybrid systems were measured as a function of mineral composition and analyzed in terms of traditional Nielsen and Cussler approaches. A modification of the Nielsen model has been proposed, which considers the effect of layer aggregation (layer stacking) on gas barrier. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1733–1753, 2007

Crumpled Graphene Nanosheets as Highly Effective Barrier Property Enhancers

“…[ 16 ] However, incomplete delamination of clay layers during the preparation of PCNs often results in thick aggregates with signifi cantly lower aspect ratios ( ∼ 2-28). [ 6 ] In contrast, not only are phenyl isocyanate-functionalized graphene sheets routinely obtained as individual sheets ∼ 1 nm thick and Figure 1 . a) Relative permeability plots for fi lms of polystyrene-graphene (represented as PGN) and polystyrene-montmorillonite (represented as PCN) [ 15 ] compared to a pristine polystyrene fi lm.…”

“…This results in an unprecedented reduction in oxygen solubility, nearly three orders of magnitude greater than the value predicted by the rule of mixtures (ROM, see Equation S6 in Supporting Information), which manifests as a considerable decrease in oxygen permeability. At such a low concentration, crumpled graphene sheets are as effective as clay-based nanofi llers at ∼ 25-130 times higher loadings [ 6 ] and one order of magnitude more effective than predicted by the modifi ed-Nielsen [ 7 ] and Cussler [ 8 ] theories. In addition, this low loading of graphene can significantly reduce the transmittance of ∼ 0.028-cm-thick polystyrene fi lms at 350 nm from 94% to 31%.…”

A review of the water barrier properties of polymer/clay and polymer/graphene nanocomposites

“…However, this may not be the case and under these circumstances, where aggregation of the clay platelets occurs due to intercalation without complete exfoliation, then the tortuous path is correspondingly reduced. Nazarenko et al [23] incorporated the effect of stacking into the Nielsen model, assuming that the stacked layers were aligned perpendicular to the diffusion direction.…”

Influência das condições de mistura e dos teores de Acetato de Vinila e de argila nas propriedades de nanocompósitos de EVA/montmorilonita organofílica

“…Já na forma de tactóides, menor será a quantidade de camadas impermeáveis distribuídas e a razão de aspecto assim calculada, será menor. A modificação da Equação 1 foi proposta por Nazarenko et al [25] onde avaliaram diferentes condições de dispersão de argila em poliestireno e apresentaram que a eficiência na redução da permeabilidade é função do número de camadas de argila nos tactóides. Isto é, para a argila totalmente esfoliada a eficiência é máxima, pois W é a espessura real de uma nanocamada de argila, mas quando há a presença dos tactóides W passa a representar a espessura do tactóide que pode conter várias nanocamadas agregadas.…”