Recent advances in dual-filler mixed matrix membranes

Mixed matrix membranes (MMMs) have been widely developed as an attractive solution to overcome the drawbacks found in most polymer membranes, such as permeability-selectivity trade-off and low physicochemical stability. Numerous fillers based on inorganic, organic, and hybrid materials with various structures including porous or nonporous, and two-dimensional or three-dimensional, have been used. Demanded to further improve the characteristics and performances of the MMMs, the use of dual-filler instead of a single filler has then been proposed, from which multiple effects could be obtained. This article aims to review the recent development of MMMs with dual filler and discuss their performances in diverse potential applications. Challenges in this emerging field and outlook for future research are finally provided.

Curing and swelling kinetics of new magnetorheological elastomer based on natural rubber/waste natural rubber gloves composites

This article proposes a new type of magnetorheological elastomer (MRE) based on natural rubber (NR) and waste natural rubber gloves (wNRg) blends. The material properties of the MRE samples were investigated with specific focus on the curing and swelling kinetics. Two different series were prepared; the first used carbonyl iron (CI) as the single filler in the MRE, whereas the second hybridized CI with carbon black (CB) to prepare an MRE resistant to solvents. The results show that most properties depend strongly on the nature of both fillers. The higher thermal conductivity of the CI caused a substantial decrease in both the scorch and curing times and the activation energy in the curing process. Based on the diffusion study, a higher volume of fillers in the rubber composites resulted in a greater area of blockage and restricted the penetration of the solvent tested throughout the composites, irrespective of whether CI alone or in combination with CB was used in the composites.

Tensile and conductivity properties of epoxy composites containing carbon black and graphene nanoplatelets

Adding conductive fillers to an insulating polymer matrix produces composites with unique properties. Varying amounts of carbon black (0.33, 0.67, and 1 wt%) and graphene nanoplatelets (5, 10, 15, and 20 wt%) were added to epoxy. In addition, a few carbon black/graphene nanoplatelet/epoxy formulations were also fabricated. The conductivity and tensile properties were determined and analyzed. The single filler composites containing 5 and 10 wt% graphene nanoplatelet and 0.33 wt% carbon black could be used for electrically insulating applications. Composites containing 15 and 20 wt% graphene nanoplatelet could be used for static dissipative applications. The following composites could be used for semi-conductive applications: 0.67 wt% carbon black/epoxy, 1 wt% carbon black/epoxy, 0.33 wt% carbon black/5 wt% graphene nanoplatelet/epoxy, and 0.33 wt% carbon black/10 wt% graphene nanoplatelet/epoxy. At the 95% confidence level, the combination of 0.33 wt% carbon black with 5 wt% graphene nanoplatelet caused the composite electrical resistivity (1/electrical conductivity) to significantly decrease from ∼1015 ohm-cm to ∼104 ohm-cm. It is likely that the highly branched, high surface area carbon black is forming an electrically conductive network with graphene nanoplatelets. Concerning single filler composites, adding ≤1 wt% carbon black did not significantly lower the composite tensile strain; however, adding graphene nanoplatelet did decrease tensile strain and increase modulus. One possible application for the 10 wt% graphene nanoplatelet/epoxy composite is in Polymer Core Composite Conductors for power transmission lines, which need to be electrically insulating, have improved thermal conductivity (increased from 0.2 to 0.3 W/m-K), increased tensile modulus (increased from 2.7 to 3.3 GPa), and good tensile strength (70 MPa) and strain (3.3%).

Thermally Conductive Polypropylene/Graphite/Carbon Fiber Composites

The combination of different carbon-based fillers (commercial plate graphite (GR) and rod carbon fiber (CF)) were added as conductive fillers to improve the thermal conductivity of polypropylene (PP). The effect of different ratio of carbon-based fillers on the thermal and mechanical properties of GR/CF/PP composites was investigated in detail. A remarkable synergistic effect between GR and CF in improving thermal conductivity of PP composites has been achieved. The results show that the in-plane thermal conductivity rises to 2.8 W·(m·k)-1 at a GR/CF ratio of 5:1 (the total mass fraction of carbon-based fillers to 40wt%), which is 14 times as the thermal conductivity of pure PP (0.2 W·(m·k)-1) and also much higher than that of single filler composites.

A Study on the Mechanical and Thermal Properties of ENR Filled with Dual Fillers

The effects of dual fillers, carbon black (CB) and mineral filler mixture (MFM) in epoxidized natural rubber (ENR) compound using BR1600 internal mixer were investigated. In this study, the processability of the compound improved and the cure time decreased with partial replacement of CB with MFM. Results also showed that compound filled with partial replacement of 20 phr of CB with MFM exhibited comparable tensile strength value with compound filled with 50 phr CB as single filler. Nevertheless, based on Thermogravimetri analysis (TGA), ENR filled with 50 phr CB gave higher char yield which can ascribe to the better stability of the char layer formed.

MIXING SEQUENCE IN NATURAL RUBBER CONTAINING ORGANOCLAY AND NANO–CALCIUM CARBONATE TERNARY HYBRID NANOCOMPOSITES

ABSTRACT Rubber nanocomposites containing one type of nanofiller are common and are widely established in the research field. In this study, natural rubber (NR) based ternary nanocomposites containing both calcium carbonate and organoclay have been characterized on the basis of morphology, cure characteristics, and physico-mechanical behavior. Natural rubber nanocomposite samples containing modified silicate (Cloisite 15A) and also nano-carbonate calcium were prepared using a laboratory internal mixer. The effect of the mixing sequence on the morphology and mechanical properties of the samples was investigated. Based on results of morphology and mechanical properties, the dual fillers phase nanocomposites (hybrid nanocomposite) perform better in comparison with single filler phase nanocomposites. The reinforcing capability of nano-CaCO3 and organoclay in NR was characterized by means of cure rheometry, morphology, and mechanical properties. NR/single filler phase and two filler phase nanocomposites were prepared by simple melt mixing method. Concentration of nano-CaCO3 and organoclay in NR was 10 and 5 parts per one hundred parts of rubber by weight, respectively. The microstructure and homogeneity of the compounds was confirmed by studying the dispersion of nanoparticles in NR via X-ray diffraction and field emission scanning electron microscopy. A more pronounced effect was achieved by using dual filler based nanocomposites as compared with single filler phase nanocomposites. The obtained results reveal that hybrid nanocomposites have more adequate morphology, rheometery, and mechanical behaviors as well as swelling resistance. The effect of mixing sequence of fillers has been studied in detail. Simultaneous addition of the two nanofillers to the NR compound would lead to better nanocomposite properties compared with other mixing sequences. Also, the results show that the mixing sequence of these nanofillers in NR has little effect on the performance of the nanocomposite.

Thermal Conductivity of Diamond-Containing Grease

As a thermal interface material, thermal grease (TG) has been extensively applied to facilitate heat dissipation in electronic devices. Despite the superior thermal conductivity of diamond, researches on diamond-containing TGs remain rare. In this study, four kinds of TGs in which diamond served as essential filler were prepared and hot disk technique was applied to measure their thermal conductivity k(TG). After two unoverlapped particle sizes were selected, the volumetric filler content, terminal group, and viscosity of a polydimethylsiloxane (PDMS) matrix were modified in sequence. Based on the preferred recipe of a single-filler TG, two double-filler TG series were prepared by retaining the large diamonds and replacing the small ones by Al2O3 or ZnO, respectively. Depending on the content, it was found that diamond was not always the best choice for small filler. The highest k(TG), which was 23 times greater than the original k(PDMS), appeared in a ZnO-containing double-filler grease (=3.52 W/mK). The prediction for the maximum attainable thermal conductivity was preliminarily supported.