Aromatic liquid transport through filled EPDM/NBR blends

In-situ interfacial compatibilization via edge-sulfurated few layer graphene during the formation of crosslinked graphene-rubber nanocomposites

Herein, we report various physico-chemical approaches to probe the nature of the interface between few layers graphene (FLG) and carboxylated nitrile rubber (XNBR) nanocomposites prepared through efficient blending of XNBR latex with an aqueous dispersion of FLG. The extent of physical interaction between FLG and XNBR was investigated using Lorentz–Park and Cunneen–Russell models. The chemical interface between FLG and sulfur crosslinked XNBR was studied using model reactions between sulfur and graphene in presence of zinc 2-mercaptobenzothiazole (ZMBT). We propose that an edge sulfurated FLG is formed, which could chemically bond with XNBR during the vulcanization process. Density Functional Theory (DFT) was employed to unravel the mechanistic insights, which support this hypothesis and suggest a kinetically favorable sulfuration of both XNBR and FLG. The formation of a chemical bond between edge-FLG and XNBR through the proposed intermediacy of sulfurated FLG leads to the observed improvement in mechanical properties of the nanocomposites.

Matrix-filler interactions and solvent sorption features of nanohydroxyapatite (nHA) embedded ethylene-co-vinyl acetate (EVA)-millable polyurethane (MPU) blends

We report the solvent sorption features and matrix filler interactions of nanohydroxyapatite (nHA) embedded ethylene-co-vinyl acetate (EVA)-millable polyurethane (MPU) blends, using toluene, xylene, and t-butylacetate as probe molecules. The EVA/MPU blends were initially loaded with different quantities of n-HA, and the interfacial interactions were evaluated through FTIR and XRD techniques. The modulation of solvent resistance was subsequently examined in terms of filler loading, temperature and molar volume of the probes. With an increase in the amount of nHA, the solvent resistance of the matrix has been found to be enhanced, with the mechanism of transport regularly deviating from the conventional Fickian mode normally followed by elastomer matrices. The Flory-Rehner equation was employed to compute the molecular mass between crosslinks (M_c) and the crosslink density (γ). The observed enhancement in the crosslink density and the degree of reinforcement has been attributed to the increased polar-polar interactions after nHA loading into the matrix. The experimentally obtained values of M_c have been compared with phantom and affine models, to identify the type of deformation happening under solvent stress. The reinforcement effect within the matrix, as a function of filler loading, has been verified by using the Kraus equation. The swelling resistance of the composites has also been verified in biological fluids in view of the possible biofield applications of the composites.

Transport features of nano-hydroxylapatite (n-HA) embedded silicone rubber (SR) systems: influence of SR/n-HA interaction, degree of reinforcement and morphology

We report the transport characteristics of silicone rubber/nano-hydroxylapatite (SR/n-HA) systems at room temperature with reference to the effects of n-HA loading, morphology and penetrant nature, using toluene, xylene, ethyl acetate and butyl acetate in the liquid phase and methanol, ethanol, 1-propanol, 2-propanol and butanol in the vapour phase as probe molecules. The interaction between the n-HA particles and SR matrix has been confirmed by FTIR analysis. As the n-HA content in the SR matrix increased, the penetrant uptake has been found to decrease. The observations have been correlated with the density and void content of the systems. Scanning electron microscopy images have been found to be complementary to the observed transport features. The reinforcement effect of n-HA particles on the SR matrix has been verified by Kraus equation. Molecular mass between the cross links has been observed to decrease with an increase in n-HA loading. The results have been compared with affine, phantom network, parallel, series and Maxwell models. The transport data have been complemented by observations on biological fluid uptake with urea, d-glucose, KI, saline water, phosphate buffer and artificial urine as the media.

Transport characteristics of organic solvents through carbon nanotube filled styrene butadiene rubber nanocomposites: the influence of rubber-filler interaction, the degree of reinforcement and morphology

The transport behaviour of some aromatic and aliphatic solvents through carbon nanotube filled styrene butadiene rubber composites has been investigated. The aim of the present work is to investigate the role of the sorption technique in analysing the compatibility and the reinforcing effect of MWCNTs as a filler in the SBR matrix. It also focuses on the investigation of the relationship between the dispersion of CNTs in the SBR matrix and its transport behaviour. The diffusion and transport of organic solvents through the membranes have been investigated in detail as a function of CNT content, nature of solvent and temperature in the range of 28-60 °C. Solvent uptake, diffusion, sorption and permeation constants were investigated and were found to decrease with the increase of CNT loading. Transport properties could be related to the morphology of the nanocomposites. At high concentration CNT particles form a local filler-filler network in the rubber matrix. As a result, the transport of solvent molecules through the polymer is hindered. The rubber-solvent interaction parameter, enthalpy and entropy of sorption have also been estimated from the transport data. The values of rubber-solvent interaction parameters obtained from the diffusion experiments have been used to calculate the molecular mass between the crosslinks of the network polymer. The better reinforcement at higher filler loading was confirmed from the cross-link density values. The extent of reinforcement was evaluated using Kraus and Cunneen and Russel equations. The Affine and Phantom models for chemical crosslinks were used to predict the mobility of the crosslinks. The Phantom model gave better fitting indicating that the chains can move freely through one another, i.e. the junction points fluctuate over time around their mean position without any hindrance from the neighbouring molecule. The diffusivity datas of the systems have shown dependence on the temperature and microstructure of the nanocomposite. Finally, the diffusion data have been compared with theoretical predictions.

XLPE based Al2O3–clay binary and ternary hybrid nanocomposites: self-assembly of nanoscale hybrid fillers, polymer chain confinement and transport characteristics

Transport mechanism through binary (A & C) and ternary hybrid (AC) XLPE nanocomposites.

Preparation and Properties of EPDM/NBR/Organoclay Nanocomposites

In this research work, three different types of nano-composites based on EPDM/NBR blend (70/30 wt.%) have been prepared: one type including Cloisite 20A in EPDM phase, the other one containing Cloisite 30B in NBR phase and the third type consisting of Cloisite 20A in EPDM and Cloisite 30B in NBR phases simultaneously (called EN-xAB). XRD and TEM techniques showed intercalated or exfoliated structures for all types of nano-composites. According to SEM results, the most roughness of the surface was observed at EN-xAB nano-composites. Cure characteristics of the samples showed that the lowest scorch and cure time and highest crosslink density was devoted to EN-xAB samples. Comparison of mechanical properties of the nano-composites showed that the best properties were found in the samples consisted of both types of organo-clays simultaneously.