Effect of different ionic liquids on the dispersion and phase selective wetting of carbon nanotubes in rubber blends

Influence of Fillers and Ionic Liquids on the Crosslinking and Performance of Natural Rubber Biocomposites

This work concerns the effect of fillers and ionic liquids on the cure characteristics of natural rubber (NR) compounds, as well as the mechanical and thermal properties of the vulcanizates. Three types of white filler were applied, such as cellulose, nanosized silica and hydrotalcite, to modify the performance of NR composites. Additionally, ionic liquids (ILs) with bromide anion and different cations, i.e., 1-butyl-3-methylimidazolium (Bmi) and 1-butyl-3-methylpyrrolidinium (Bmpyr), were used to improve the cure characteristics of NR compounds and functional properties of the vulcanizates. The type of filler and the structure of ILs were proved to affect the rheometric properties and cure characteristics of NR compounds as well as the performance of the NR vulcanizates. Owing to the adsorption of curatives onto the surface, silica reduced the activity of the crosslinking system, prolonging the optimal vulcanization time of NR compounds and reducing the crosslinking degree of the elastomer. However, silica-filled NR exhibited the highest thermal stability. Hydrotalcite increased the crosslink density and, consequently, the mechanical properties of the vulcanizates, but deteriorated their thermal stability. ILs beneficially influenced the cure characteristics of NR compounds, as well as the crosslink density and mechanical performance of the vulcanizates, particularly those filled with silica. Cellulose did not significantly affect the vulcanization of NR compounds and crosslink density of the vulcanizates compared to the unfilled elastomer, but deteriorated their tensile strength. On the other hand, cellulose improved the thermal stability and did not considerably alter the damping properties of the vulcanizates.

Synergistically Boosting Thermoelectric Performance of PEDOT:PSS/SWCNT Composites via the Ion-Exchange Effect and Promoting SWCNT Dispersion by the Ionic Liquid

Poly(3,4 ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is perhaps the most successful polymer material for thermoelectric (TE) applications. So far, treatments by high-boiling solvents, acid or base, or mixing with the carbon nanotube (CNT) are the main ways to improve its TE performance. Herein, we report the synergistically boosting TE properties of PEDOT:PSS/single-walled CNT (SWCNT) composites by the ionic liquid (IL). The composites are prepared by physically mixing the SWCNT dispersion containing the IL with PEDOT:PSS solution and subsequent vacuum filtration. The IL additive has two major functions, that is, inducing the phase separation of PEDOT:PSS and a linear quinoid conformation of PEDOT and promoting the SWCNT dispersion. The maximum power factor at room temperature reaches 182.7 ± 9.2 μW m^-1 K^-2 (the corresponding electrical conductivity and Seebeck coefficient are 1602.6 ± 103.0 S cm^-1 and 33.4 ± 0.4 μV K^-1, respectively) for the free-standing flexible film of the PEDOT:PSS/SWCNT composites with the IL, which is much higher than those of the pristine PEDOT:PSS, the IL-free PEDOT:PSS/SWCNT, and the SWCNT films. The high TE performance of composites can be ascribed to synergistic roles of the ion-exchange effect and promotion of SWCNT dispersion by the IL. This work demonstrates the dual roles for the IL in regulating each component of the PEDOT:PSS/SWCNT composite that synergistically boosts the TE performance.

New Flame Retardant Systems Based on Expanded Graphite for Rigid Polyurethane Foams

The effect of the addition of new flame retardant systems on the properties of rigid polyurethane (RPUF) foams, in particular, reduction in flammability, was investigated. The modification included the introduction of a flame retardant system containing five parts by weight of expanded graphite (EG) (based on the total weight of polyol), one part by weight of pyrogenic silica (SiO2) and an ionic liquid (IL): 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim] [BF4]), in an amount of 3:1 with respect to the weight of added silica. The kinetics of the synthesis of modified foams—including the growth rate and the maximum temperature—were determined and the physicochemical properties, such as the determination of apparent density and structure by optical microscopy, mechanical properties such as impact strength, compressive strength and, three-point bending test were determined. An important aspect was also to examine the thermal properties such as thermal stability or flammability. It has been shown that for rigid polyurethane foams, the addition of expanded graphite in the presence of silica and ionic liquid has a great influence on the general use properties. All composites were characterized by reduced flammability as well as better mechanical properties, which may contribute to a wider use of rigid polyurethane foams as construction materials.

Effect of Magnetic Field and Aggregation on Electrical Characteristics of Magnetically Responsive Suspensions for Novel Hybrid Liquid Capacitor

Magnetically responsive fluid based on polymers of natural rubber (NR-latex) involves a magnetic compound fluid (MCF) rubber liquid. For a wide range of engineering applications of suspensions or liquids with particles, their electrical characteristics of fluidic suspensions are investigated to obtain useful results that might be important in the study of devices, such as fluidic sensors and capacitors. The author of the present paper proposes that MCF rubber liquid can be produced by combining MCF and rubber latex. The influence of the aggregation of magnetic particles and rubber molecules on electrical characteristics under a magnetic field was investigated by measuring electrical properties under an applied voltage. The electrical characteristics change with a linear or a nonlinear response, based on conditions of particle aggregation. The capacity of the electric charge also changes with the conditions of particle aggregation. These results show that MCF rubber liquid is a novel hybrid capacitor.