Influence of processing parameters on barrier properties of nitrile rubber/nanoclay nanocomposite membrane against organic solvent

Abstract

The present study focuses on the influence of layered silicate nanoparticles on barrier properties of a rubber/nanoclay nanocomposite (RCN). Most of the previous works deal with the importance of the surface chemistry of the nanoclay on the performance of the material. In this paper were rather investigated the effect of the processing conditions. Elastomer nanocomposites based on nitrile butadiene rubber and layered silicate nanoparticles were prepared using three different techniques: chemical dissolution, mixing in an internal mixer and melt-mixing with a twin-screw extruder. Chemical resistance to methanol was assessed using gravimetric method and mass transfer kinetic parameters were then deduced. Mass uptake results clearly showed that extruded RCN exhibited the highest chemical resistance. Barrier properties were subsequently correlated to the morphological structure of the rubber/nanoclay system. Small-angle X-ray diffraction patterns indicated that this improvement was due to a preferred alignment of the nanoparticle in the structure. Further, inspection revealed an anisotropic orientation profile of the nanoclay layers over the thickness of a sheet-like extruded material. In addition, a neat decrease of chemical sorption was spotted with mixing and chemically processed RCN materials over the unfilled rubber. The state of dispersion of clay nanoparticles was also probed in these nanocomposites using X-ray diffraction. The findings suggested an intercalation during processing. Further, transmission electron microscopy observations were suggesting a bimodal state of dispersion over spotting individual nClay platelets along with the layered stacks. Improvement of mass transport kinetic parameters was recorded over increasing the shear stress as well as the residence time when RCN were prepared in the internal mixer.

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