Silicone Microemulsions Research Articles

The effect of surface and porous structure on long-term performance of carbon powder cathodes without binder, during a 300-day trial in microbial fuel cells

The performance of microbial fuel cell (MFC) highly depends on the selection of appropriate electrode materials, in particular – cathodes. Herein, two different activated carbons (CWZ-22 and CWZ-35) without binder, as well as the activated carbon modified with silica nanoparticles (CWZ-22/Si), were used to improve the performance of air cathodes. Nearly one year of operation of materials varying in surface area and microporous structure revealed significant differences in their dynamic behaviour. CWZ-22 with lower surface area and a smaller micropore size, reached an internal resistance (Rint) of 162 Ω, and a maximum power density of 23.3 W m−3. CWZ-22/Si, coated with silane-siloxane-based silicone microemulsion displayed a drop of maximum power generation by 10%. CWZ-35, with higher surface area, but also higher micropore size, displayed 22.8 W m−3 and Rint of 159 Ω. The monitoring of electrochemical and performance parameters indicated an improved long-term behaviour of the cathodes in the following order: CWZ-22 > CWZ-22/Si > CWZ-35. This is the first work in which the pore size distribution and surface area are demonstrated to have a long-term impact on cathodic fouling, and, depending on these properties, this impact may be either positive or negative on MFC performance.

In Situ Monitoring of Drying Process of Masonry Walls

The in situ hygro-thermal behavior of a wet masonry wall during its drying process is presented in this paper. The considered wall is a part of a basement of a historic building that was subjected to renovation works. The building is located in the City of Łowicz (Poland). The drying process was implemented by applying the thermo-injection method and a novel prototype of the drying device used for this method. The dedicated acquisition system was developed to in situ monitor parameters of the drying process. The air temperature and relative humidity in various locations in the basement, temperatures and moisture contents at several points of the wet wall as well as the electrical parameters of the drying device were registered. Based on variations of the monitored parameters, the hygro-thermal behavior of the wall during drying was studied. After 6 days of drying, the wall temperature in the drying zone was increased to approximately 40–55 °C, while the moisture content was reduced to the mean level of 3.76% vol. (2.35% wt.). These wall parameters allowed for effective impregnation of the wall with the hydrophobic silicone micro-emulsion, which created horizontal and vertical waterproofing. Moreover, the specific energy consumption during the drying process defined as energy consumption divided by the mean volumetric moisture content drop (MC) between the initial and final state in the wall and by the length of the dried wall section was estimated to be 11.08 kWh/MC%/m.

Improved reactive dye fixation on ramie fiber in liquid ammonia and optimization of fixation parameters using the Taguchi approach

Dyeing in liquid ammonia has the advantage of penetrating the reactive dye molecules inside the fiber structure by modifying the cellulose supramolecular from a crystalline to amorphous form. However, the dye fixation rate of the baking treatment is unsatisfactory (29.45%). In this study, ramie yarn hanks were dyed in liquid ammonia, and cationic fixation auxiliary silicone micro-emulsion was used to fix the dye molecules in the fibers to improve the dye fixation rate and fastness properties. The fixation parameters were optimized using the Taguchi approach. The optimum conditions of the cationic fixation auxiliary mass, fixation time, and water content with four levels on the fixation rate were investigated using an L16 orthogonal array. The larger-the-better signal-to-noise ratio was applied to maximize the responses of the parameters. The main effect and interaction plot of several factors were analyzed, with results suggesting that the mass of the cationic fixation auxiliary is the most influential parameter for the fixation of the reactive dye (P < 0.05). A fixation rate for the reactive dye of 52.82% ± 0.5% was observed under the optimal conditions. The color uniformity, wash fastness and rubbing fastness of the dyed sample treated by the cationic fixation auxiliary silicone micro-emulsion were exceptional.

WACKER presented two silicone microemulsions at PCHi 2018

WACKER presented two silicone microemulsions at PCHi 2018

BRB's new silicone microemulsion for sealants offers long-lasting protection

BRB's new silicone microemulsion for sealants offers long-lasting protection

Silicone Microemulsion Structures Are Maintained During Polymerization with Reactive Surfactants

Bicontinuous microemulsions exhibit domain structures on the nanoscale (<20 nm). Normally, such fine details are lost during the conversion from a fluid microemulsion to solid elastomeric materials, as a consequence of interfacial destabilization via polymerization of either the oil phase or monomers in the aqueous phase. Very little is known about the polymerization of silicone microemulsions and the morphological changes that occur upon transition from a nanostructured liquid to a solid matrix. Silicone microemulsions polymerized by free radical (aqueous phase) and condensation (silicone phase) processes, respectively, were characterized by small-angle X-ray scattering and transmission electron microscopy. It was found that cross-linking of the silicone phase alone led, over time, to large increase of the size of the microemulsion nanodomains. By contrast, photoinduced polymerization of a reactive surfactant and acrylic monomers in the aqueous phase was effective at retaining bicontinuous nanomorphology, irrespective of the degree of cross-linking of the silicone phase.

Nanodomains within bicontinuous silicone/water microemulsions retard TiO2 nanoparticle aggregation

Nanoparticles of TiO2 are used in a variety of applications because of their high refractive index and photocatalytic behaviour. We report that both the interactions between the surfactant and titanium alkoxide and templating provided by a microemulsion significantly retard the formation of visible TiO2 aggregates. TiO2 nanoparticles (<30nm) were prepared under mild, neutral conditions within water-in-oil and bicontinuous silicone microemulsions. The particles aggregated only slowly, as shown by UV absorption spectroscopy transmission electron microscopy, and particle sizing. Retarded particle growth is ascribed primarily to constricted domains provided by self-organization within a water/surfactant/silicone microemulsion.

Nanotechnologia – perspektywy i osiągnięcia w badaniach i konserwacji dzieł sztuki

Nanotechnology – perspectives and achievements in research and conservation of the works of art This paper is an overview discussing nanotechnology as a dynamically develop ing interdisciplinary fild, offering in recent years new tools and materials also for conservation of the works of art. The origin and defiitions of nanotechnolo gy and nanomaterials are presented as well as classifiation of nanoobjects along with examples and signifiance of the presence of nanostructures in the nature and in historical artworks. The role of microscopy in studying and designing nao structures is underlined. The processes of manufacturing nanomaterials with „topdown” and „bottom-up” methods are characterised. Some examples of employing nanostructures in conservation of the works of art are presented, such as Rusing silicone microemulsions for hydrofobisation of stone materials, using fitering and magnetic gels for cleaning of paintings, using nanoparticulate TiO2 for manufac turing self-cleaning facade paints or using nanolime for deacidifiation of paper and canvas and for consolidation of mineral supports and paint layers. Readers’ attention is drawn to the possibility of incorporating nanoparticles into other materials and partial modifiation of their properties. The results of microscop ic analysis of the Nanorestore lime are presented. They have revealed, that nan oparticles of that material quickly accumulate into aggregates and agglomerates, which results in loosing the properties of a nanomaterial. The present achieve ments of nanotechnology in the fild of research and conservation of the Works of art are evaluated, the perspectives are drawn and the directions of further ex - pected research are indicated.

Multifunctional finish and cotton cellulose fabric

Some commercial textile softeners were incorporated during the finishing of cotton fabrics with citric acid (CA) leading to alteration in performance properties of that fabrics. The obtained results showed that finishing of these fabrics with 80g/l of aqueous CA in presence of 20g/l of silicone micro emulsion (SME) followed by drying at 85°C for 3min, cured at 180°C for 90s resulted in crosslinking as well as an improvement in some performance properties of those fabrics such as nitrogen content, resiliency, tear strength and softness of the finished fabrics accompanied with decreasing of the whiteness indices and absorbency of that fabrics. Moreover, infrared spectrum as well as TGA analysis of CA/SME finished fabrics was investigated. Furthermore, the CA/SME finished fabrics were able to keep the Rosemary, Jasmine, Lavender and vanillin perfumes upon storing up to 3 months or after ten repeating washing cycles.

Elastomeric hydrogels by polymerizing silicone microemulsions

Robust, transparent elastomeric hydrogels encoded with a bicontinuous structure result from the sequential photopolymerization of the aqueous hydroxyethyl methacrylate phase and crosslinking of the silicone phase of a silicone microemulsion stabilized with an acrylate-functional silicone-poly(ethylene glycol) surfactant.

An eco-friendly – novel approach for attaining wrinkle – free/soft-hand cotton fabric

A novel approach for upgrading both the wrinkle free and softness properties of cotton fabrics without adversely affecting their strength properties using an eco-friendly finishing regimes was investigated. Factors affecting the performance properties of the finished substrate such as pre-treatment, i.e., carboxymethylation (CMC) or ionic-crosslinking, post-treatment with amino functional silicone softener and its concentration, degree of carboxymethylation as well as thermofixation conditions were studied. The obtained results revealed that post-treatment with the amino based silicone micro emulsion (SiE) up to 30 g/L at pH 4 to a wet pickup of 100% followed by drying at 100 °C for 5 min and curing at 170 °C for 3 min results in a remarkable improvement in fabric resiliency (expressed as dry and wet wrinkle recovery angles), as well as in softness degree, without seriously affecting its retained strength. Improvement extent of the aforementioned properties is governed by the nature of the pre-treatment steps. Fixation of the amino-functional silicone softener onto/or within the modified cellulose structure is accompanied by a formation of semi-inter and/or intra-penetrated network (semi-IPN) thereby enhancing both the extent of crosslinking and networking as well as providing very high softness. FTIR analysis proved the formation of Si–O–Si–cellulose complex. Scanning electron micrograph shows that cotton, CMC and ionic crosslinked cotton fabrics treated with SiE shows higher surface smoothness and considerable reduction in protruding loose fibers, ditches and grooves compared with the untreated one.

The efficacy of commercial silicones against blue stain and mould fungi in wood

Scots pine (Pinus sylvestris L.) samples were vacuum pressure impregnated with quaternary ammonium (quat)-silicone micro-emulsion (<40 nm particle size), amino-silicone macro-emulsion (110 nm) and silicone macro-emulsion with alkyl modified side groups (740 nm). Quat-silicone micro-emulsion caused highest cell wall bulking (4.8%) and anti-swelling efficiency (21.8%) in wood when treated with 30% concentration of silicone in the treatment solution. All three formulations made wood hydrophobic which was evident from a capillary (longitudinal, tangential and radial) water uptake test. Amino-silicone macro-emulsion (10% silicone in treatment solution) resulted in strong resistance to blue stain attack with both pre-weathered and not pre-weathered wood samples. Signs of blue staining were more evident on the pre-weathered samples. Treatment with amino-silicone macro-emulsion (10% silicone in treatment solution) resulted in a certain resistance to mould growth on wood surfaces, whereas wood treated with the same concentration of quat-silicone micro-emulsion and alkyl-modified silicone macro-emulsion exhibited comparatively lower resistance.

Silicon-Microemulsions-Konzentrate / Silicone Microemulsion Concentrates

The technology of silicone microemulsion concentrates eliminates for the first time the use of organic solvents in the hydrophobic impregnation of mineral building materials and coatings, in coating-priming and in wall-drying by drill hole injection. Water-based silicone microemulsions meet the requirements such as effectiveness, durability, aplication, toxicity and ecology. The use of water instead of organic solvents and the modern concentrate technique make an effective contribution to environmental protection.