CO2 sorption and diffusion in polymethyl methacrylate-clay nanocomposites

Abstract

This study reports the glass transition temperature (T g ), and sorption and diffusion of subcritical CO 2 gas in polymethyl methacrylate (PMMA) nanocomposites containing organically modified smectite clay, Cloisite 20A (C20A). A range of methods for preparing the PMMAclay nanocomposites was investigated and a solution coprecipitation method was selected as the most appropriate. Using this method, PMMA nanocomposite containing 2, 4, 6, and 10 wt% nanoclay loadings were prepared. Wide-angle X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) indicated that the 2 wt% nanocomposite materials had a well-dispersed intercalated clay structure. The T g for PMMA-C20A nanocomposites, as measured by differential scanning calorimetry (DSC), was found to be independent of the clay loading. CO 2 solubility studies from 0 to 65°C and pressures up to 5.5 MPa using an in situ gravimetric technique were performed on compression-molded films. The organoclay was found to have no effect on the solubility of CO 2 in PMMA, and therefore the solubility of CO 2 in the nanocomposite can be determined from the solubility of CO 2 in the matrix polymer alone. Diffusion coefficients were determined using the appropriate transport models for these test conditions and the diffusion coefficients for CO 2 in PMMA-C20A composites were found to increase with organoclay loading. It is believed that the processing path taken to prepare the nanocomposites may have resulted in the agglomeration of the C20A organoclay, thereby preventing the polymer chains from fully wetting and intercalating a large number of clay particles. These agglomerations are responsible for the formation of large-scale holes within the glassy nanocomposite, which behave as low resistance pathways for gas transport within the PMMA matrix. POLYM. ENG. SCI., 45: 904 -914, 2005.

Crumpled Graphene Nanosheets as Highly Effective Barrier Property Enhancers

“…We note that our smallest observed relative increase in density (1.05% for 0.02 vol% graphene loading) was only approached in these studies after nearly 10 000 hours of aging at 35 ° C. [ 28 ] For comparison, poly(methyl methacrylate)-MMT composites containing 1.3 and 2.7 vol% of clay nanofi ller only exhibit densifi cations of 0.63 and 1.37%, respectively, according to the ROM. [ 29 ] …”

Recent Developments in the Permeability of Polymer Clay Nanocomposites

“…The sorption behavior is described by Henry's law: 6) where C D is the concentration of sorbed gas, k D is Henry's coefficient or Henry's solubility, and p is the partial pressure of the gas. This represents the gas molecules that exist in the dissolved state (between the polymer chains) and is related to the fluctuating fraction of the free volume of the polymer [6,7]. The subscript "D" denotes the dissolved state.…”

Gas Sorption into Surface of Poly(methyl methacrylate) Films at Atmospheric Pressure

“…[18][19][20] They have concluded that polymers containing carbonyl groups would act as an electron donor, and that a specific intermolecular interaction between the polymer and CO 2 , which behaves as an electron acceptor rather than as an electron donor, is attained. 20 Although a weak electrostatic interaction 21 is possible to a pair of CO 2 and phenyl -electrons of PS, PS does not show a strong interaction with CO 2 owing to a lack of carbonyl groups. These arguments are consistent with what is seen in Figure 5.…”