Dual Transient Networks of Polymer and Micellar Chains: Structure and Viscoelastic Synergy

Dual transient networks were prepared by mixing highly charged long wormlike micelles of surfactants with polysaccharide chains of hydroxypropyl guar above the entanglement concentration for each of the components. The wormlike micelles were composed of two oppositely charged surfactants potassium oleate and n-octyltrimethylammonium bromide with a large excess of anionic surfactant. The system is macroscopically homogeneous over a wide range of polymer and surfactant concentrations, which is attributed to a stabilizing effect of surfactants counterions that try to occupy as much volume as possible in order to gain in translational entropy. At the same time, by small-angle neutron scattering (SANS) combined with ultrasmall-angle neutron scattering (USANS), a microphase separation with the formation of polymer-rich and surfactant-rich domains was detected. Rheological studies in the linear viscoelastic regime revealed a synergistic 180-fold enhancement of viscosity and 65-fold increase of the longest relaxation time in comparison with the individual components. This effect was attributed to the local increase in concentration of both components trying to avoid contact with each other, which makes the micelles longer and increases the number of intermicellar and interpolymer entanglements. The enhanced rheological properties of this novel system based on industrially important polymer hold great potential for applications in personal care products, oil recovery and many other fields.

The Effect of Arachidic Acid Mixtures on the Cooling Performance of a Heat Sink

The temperature of an electronic device is one of the most important parameters to deal with. Any increase above the temperature limits results in a failure in the device. Thus, to ensure good operation, an electronic device should be cooled. One promising technique is the use of Phase Change Materials (PCMs) for their well-known ability to absorb the heat dissipated by the device, thanks to their high latent heat of fusion. Arachidic acid is a fatty acid that, when mixed with sodium decanoate and potassium oleate salts, can be used as a promising PCM due to its high latent heat. This paper aims to shed light on the use such mixtures of Arachidic acid for cooling in a heat sink. An experimental setup was built for this purpose. The results show that the Arachidic acid mixtures are suitable for applications requiring intermediate heat dissipation.

Preparation of Magnesia Insulation Materials by Calcination of Walnut Shell Powder by Silica Sol Impregnation

In this paper, magnesia porous aggregate was prepared by the foaming method with potassium oleate as the foaming agent. Secondly, the walnut shell powder was impregnated with the silica sol as the pore forming agent, and then, a new magnesia insulation material was prepared by 1300°C sintering. By changing the amount of the walnut shell powder added, the mechanical properties and thermal properties of the materials after sintering were studied. The results show that the sample with 10% walnut shell powder impregnated without the silica sol has a compression strength of 12 MPa. A sample with 10% walnut shell powder treated with the silica sol has a compression strength of 18 MPa. With the increase in the amount of the walnut shell powder added after impregnation, the bulk density, compression strength, and thermal conductivity of the sample all showed a decreasing trend, and the apparent porosity showed an increasing trend. When the additive amount is 20%, the bulk density of the sample is 1.029 g/cm3, and the thermal conductivity is 0.382 W/m K (1050°C).

Advanced Loop Thermosiphon With Check Valve (ALT/CV): Thermal Performance and Behavior

Nanofluids (NFs) are an attractive alternative to traditional working fluids for thermosiphons, but the solid nanoparticles (NPs) within the NF can agglomerate and reduce the thermal performance. This study focused on clarifying the effect of a NF with surfactants on the heat transfer characteristics of an advanced loop thermosiphon with a check valve (ALT/CV). In an experiment, the ALT/CV was filled with different working fluids at filling ratios of 30%, 50%, and 80% with respect to the evaporator volume. Heat was supplied at 20%, 40%, 60%, 80%, and 100% of the heater output (2000 W). Five working fluids were considered: deionized (DI) water, a DI water-based NF with 0.5 wt% silver NPs, and the same NF containing 0.5, 1, and 1.5 wt% oleic acid (OA) and potassium oleate (OAK+) as surfactants. The results showed that the ALT/CV provided a better heat transfer performance than a normal thermosiphon. The maximum heat transfer rate was achieved with the NF containing 0.5 wt% silver NPs and 1 wt% OAK+. The NF containing OAK+ demonstrated a heat transfer rate approximately 80% higher than that of the DI water

Development and characterization of biodegradable polymeric composites based on butadiene-co-acrylonitrile rubber and functionalized postconsumer wood waste

In a circular economy, the value of products and materials is maintained as much as possible; waste and resource use are kept to a minimum, and resources do not leave the economic flow once they reach the end of their life, but are reused and create further value. The paper presents the obtaining and characterization of a composite based on butadiene-co-acrylonitrile rubber - continuous phase, where are added post-consumer recycled wood particles, with dimensions of 500 nm - discontinuous phase, and ingredients, such as: active fillers, plasticizers, vulcanizing agents, antioxidants. Wood waste acts as a filling material which leads to the biodegradability of the composite and the decrease in density. The small size of the waste particles and their functionalization with potassium oleate leads to the formation of bonds between the matrix and the particles so that the physical-mechanical characteristics of the composite correspond to the requirements of the products obtained from it.

Designing and obtaining wood waste and chloroprene rubber-based composites

The aim of this paper is to obtain and study the properties of wood waste reinforced elastomer composites with various fibre contents (10-50 wt%). The composite is based on chloroprene rubber, and added post-consumer recycled wood particles, with dimensions of 500 nm eco-reinforcing material, and active fillers, plasticizers, vulcanizing agents, antioxidants. In order to enhance the compatibility and their level of interaction, the wood waste was finely ground (cryogenic mill) and functionalized with potassium oleate. Wood waste acts as a filling material which leads to the biodegradability of the composite and the decrease in density. Tensile, tear strength, elasticity, hardness, abrasion resistance, melt flow index and morphological study (FT-IR) of those composites were examined in order to determine the viability in various applications domains.