Search Results (13)

Coffee is one of the most consumed commodities globally, and its harvests generate large quantities of wood waste with low industrial value. This study aimed to explore the potential of residual Coffea arabica wood to produce lignocellulose microfibrils and lignocellulose nanofibrils (LCMF/LCNF) and biodegradable films with possible application in packaging. The fibers were treated with 5% NaOH and fibrillated in an ultrarefiner until they formed a gel. The resulting suspensions were used to create films whose physical, morphological, optical, and mechanical properties were analyzed. The NaOH treatment removed extractives and exposed hemicelluloses, allowing the gel point to be reached with just seven passes through the ultrarefiner, saving energy (~4700 kWh/t). More than 65% of the fibers had diameters of less than 100 nm and little sedimentation after 8 h. The films were flexible, thin (24.5 µm), with a high density (~1100 kg/m³) and good resistance to grease, as well as a water vapor permeability of ~1230 g/m²/day, suitable for packaging bread, fruit, and vegetables. However, the higher wettability of the surface may limit its use in humid environments. The films showed moderate tensile strength (~25 MPa) but low puncture resistance (~7 N mm), making them suitable for biodegradable packaging. Full article

Optical instruments require extremely high precision, and even minor surface contamination can severely impact their performance. Peelable coatings offer an effective and non-damaging method for removing contaminants from optical surfaces. In this study, an amphiphilic polyacrylate copolymer (PMLEA) was synthesized via solution radical copolymerization using the lipophilic monomer lauryl acrylate (LA) and hydrophilic monomers ER-10, methyl methacrylate (MMA), and butyl acrylate (BA). The structure and molecular weight of the copolymer were characterized using Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC). The hydrophilic–lipophilic balance, surface tension, and wettability of the copolymer were analyzed through water titration, the platinum plate method, and liquid contact angle tests. The cleaning performance of the copolymer coating on quartz glass surface contaminants was evaluated using optical microscopy and Ultraviolet-Visible Near-Infrared (UV-Vis-NIR) spectroscopy. The study examined the effect of varying the ratio of LA to ER-10 on the hydrophilicity, lipophilicity, cleaning efficiency, and mechanical properties of the copolymer coating. The results showed that when the mass ratio of LA to ER-10 was 1:2, the synthesized copolymer exhibited optimal performance in removing dust, grease, and fingerprints from quartz glass surfaces. The coating had a tensile strength of 2.57 MPa, an elongation at break of 183%, and a peeling force of 2.07 N m⁻¹. Full article

In the field of high-end equipment, the synergistic effect of friction-reducing agents plays an important role in the performance study of gel grease. Exploring its tribological and rheological properties can not only significantly reduce the coefficient of friction of mechanical components and enhance its viscosity at high temperatures but also effectively reduce energy consumption, thus improving the service life of high-end equipment. In this study, Schaeffler Load 460 gel grease was mixed with polysiloxane viscosity modifier (PV611) and molybdenum dialkyl dithiocarbamate (RFM3000) according to (3:1, 1:1, and 1:3), and its tribological properties and rheological properties were investigated by the MRS-10G friction and wear tester, MCR302 rotational rheometer, and crossover test. Comparative analyses of tribological and rheological properties were carried out. The results showed that the average coefficient of friction of Schaeffler Load 460 grease was reduced by 57.2%, 60%, and 71.9%, respectively, with the addition of two different ratios of friction reducers; the average diameter of abrasive spots was reduced by 44.5%, 55.4%, and 61.3%; and the shear stress and viscosity were increased by 117.94 Pa and 1295.02 mPa∙s, respectively, compared with that of the original grease, which is a good example for the lubrication of gel grease in the high-end equipment industry. This study provides a new direction and idea for the lubrication research of gel grease in the high-end equipment industry. Full article

The progress in polymer science and nanotechnology yields new colloidal and macromolecular objects and their combinations, which can be defined as complex polymer materials. The complexity may include a complicated composition and architecture of macromolecular chains, specific intermolecular interactions, an unusual phase behavior, and a structure of a multi-component polymer-containing material. Determination of a relation between the structure of a complex material, the structure and properties of its constituent elements, and the rheological properties of the material as a whole is the subject of structural rheology—a valuable tool for the development and study of novel materials. This work summarizes the author’s structural–rheological studies of complex polymer materials for determining the conditions and rheo-manifestations of their micro- and nanostructuring. The complicated chemical composition of macromolecular chains and its role in polymer structuring via block segregation and cooperative hydrogen bonds in melt and solutions is considered using tri- and multiblock styrene/isoprene and vinyl acetate/vinyl alcohol copolymers. Specific molecular interactions are analyzed in solutions of cellulose; its acetate butyrate; a gelatin/carrageenan combination; and different acrylonitrile, oxadiazole, and benzimidazole copolymers. A homogeneous structuring may result from a conformational transition, a mesophase formation, or a macromolecular association caused by a complex chain composition or specific inter- and supramolecular interactions, which, however, may be masked by macromolecular entanglements when determining a rheological behavior. A heterogeneous structure formation implies a microscopic phase separation upon non-solvent addition, temperature change, or intense shear up to a macroscopic decomposition. Specific polymer/particle interactions have been examined using polyethylene oxide solutions, polyisobutylene melts, and cellulose gels containing solid particles of different nature, demonstrating the competition of macromolecular entanglements, interparticle interactions, and adsorption polymer/particle bonds in governing the rheological properties. Complex chain architecture has been considered using long-chain branched polybutylene-adipate-terephthalate and polyethylene melts, cross-linked sodium hyaluronate hydrogels, asphaltene solutions, and linear/highly-branched polydimethylsiloxane blends, showing that branching raises the viscosity and elasticity and can result in limited miscibility with linear isomonomer chains. Finally, some examples of composite adhesives, membranes, and greases as structured polymeric functional materials have been presented with the demonstration of the relation between their rheological and performance properties. Full article

The gel-state grease plays a vital and indispensable role in the long-term operation of wind turbines. To reduce carbon emissions and increase the reliability of wind turbines, this paper takes the gel-state Mobil SHC 461WT grease as the study object. Firstly, the rheological properties of the gel-state Mobil SHC 461WT grease were investigated using the Anton Paar MCR302 rotational rheometer. Secondly, the rheological characteristics of three different gel states of the Mobil SHC 461WT grease (additive content of 0.1% of RFM3000, SK3115, and PV611, respectively, in the gel-state Mobil SHC 461WT grease) were optimized under the same conditions. Finally, according to the experimental results and the Herschel–Bulkley (H–B) model, the RFM3000 additive has the best effect on improving the rheological characteristics of the gel-state Mobil SHC 461WT grease. This research provides a new idea and direction for the technological advancement of the gel-state grease industry. Full article

High-performance greases typically consist of a base oil and polyurea as a thickener material. To date, few alternatives to polyureas have been investigated. Polyesters could be one such alternative; however, little is known about the gelation of such polyesters because, unlike polyureas, they cannot form hydrogen bonds between the polymer chains. Here, we present studies on the gel formation of a polyester based thickener poly(hexane dodecanoate) with 1-octanol endgroups in three different base oils, i.e., a mineral oil (Brightstock 150), a synthetic Polyalphaolefin (Spectrasyn 40) and castor oil (85 to 90 wt.% ricinoleic acid triglyceride). Small- and wide-angle X-ray scattering measurements indicate a strong interaction of the polyester with castor oil and an increase in the crystalline fraction, with an increasing polymer amount from 5 to 40 wt.%. Moreover, infrared analysis of the polyester in castor oil showed gel formation at a minimum concentration of 20 wt.%. The strong interaction of the polyester with castor oil compared to the other two base oils led to an increase in the yield point γ_F as a measure of the mechanical stability of the gel, which was determined to be 5.9% compared to 0.8% and 1.0% in Brightstock and Spectrasyn, respectively. Full article

An increase in energy consumption and the extended use of nonrenewable fossil fuels raises the need to develop alternative fuels as an energy supply that can protect the environment from unwanted emissions of pollutants. One alternative renewable fuel is biodiesel. Currently, most biodiesel feed sources are edible oils, but using them leads to the dilution of global food sources. The present study aims to find an effective method of biodiesel production using food industry fatty wastes called brown grease (BG). BG contains fats, mainly linoleic and oleic free fatty acids (FFAs), that can serve as raw materials for biodiesel production using esterification reactions. The esterification and transesterification reactions for biodiesel production were studied using commercial FFAs, commercial glyceryl trilinoleate (trilinolein), soybean oil, and BG. The reactions were carried out under ultrasonic activation using BF₃ and AlCl₃ Lewis acids as catalysts in both free and immobilized forms when immobilization was performed in silica matrices using the sol-gel synthesis route. Biodiesel production was examined in batch and continuous flow reactors. The BF₃ catalyst was more efficient at the initial stages of the continuous operation, reaching a maximum conversion of 90%, with a gradual decrease in efficiency after 15 h of the process. The AlCl₃ catalyst showed better stability, reaching maximum yields of 97% and maintaining efficiency until the end of the experiment. The proposed method offers an efficient and easy way to produce biodiesel from a variety of lipids sources, including fatty wastes (BG). Full article

Magnetorheological (MR) materials are a group of smart materials used in new technologies with controlled reliability. The development of these materials is expanding, starting from MR fluids, elastomers, grease, and gel. This large number of material types further expands the various applications of MR materials as a creative technology to support performance enhancement. For example, MR fluid is used to improve the performance of shock absorbers such as vehicle suspension, the damping of building structures, and polishing of the workpiece. MR elastomers are used for engine mounting, insulation base, and many other applications with intelligent material properties such as stiffness controllability. However, there are still complexities in the practical implementation of the control system beyond reliability. Many previous studies have focused on the performance improvement and reliability of MR materials as smart materials for application devices and systems. In this review article, the specific discussion related to vibration control strategies in MR material-based systems was thoroughly investigated. To discuss this point, many MR applications including transportation system and vibration isolation were adopted using different types of control strategies. Many different control strategies that have been used for MR applications such as fuzzy logic control, optimal control, and skyhook control are discussed in-depth in terms of the inherent control characteristics of merits and demerits. Full article

The findings and technological developments related to intelligent materials are increasingly attracting the attention of scientists. One such field is that of magnetorheological (MR) materials. Scientific studies on MR materials have been carried out to determine the performance and characteristics of, for example, MR dampers, MR elastomers, and MR foams. To the best of the authors’ knowledge, there has been no statistical discussion in the form of bibliometric analyses of developments in the field of MR materials in the last ten years. This is fascinating, considering that bibliometric studies have considerable impacts and contributions, such as studies on the growth of research patterns, avoiding the repetition of research topics, and analyzing future research. This also supports the future sustainability of the topic of MR materials, helping to bridge the gap that has probably existed since the introduction of MR materials. The relationship between the authors’ scientific research, domestic and global collaborations, and the evolution of themes over the last few years is also shown in this analysis. Thus, this study aimed to fill the gap in such materials by conducting a bibliometric analysis of 1830 articles related to MR materials published over the last 10 years. The results indicated that the field of MR materials has exhibited good growth. The introduction of MR fluid materials to new types of MR materials is still in the early stages of research, such as in applications with MR foam. Further analysis showed that there is a connection and dominance of scientific publications related to MR technology. Furthermore, based on bibliometric analysis, dominant theme changes in the area of MR elastomers, particularly related to carbonyl iron particles and MR polishing, is seldom mentioned, as is also the case for MR gels, MR foam, and MR grease. However, the discussion of new MR materials is a good opportunity to promote developments in the field of MR materials. Full article

This study reports on a novel strategy for manufacturing thickened gel-like castor oil formulations by dispersing electrospun lignin/ethylcellulose nanostructures. These thickened formulations were rheologically and tribologically evaluated with the aim of being proposed as alternative ecofriendly lubricating greases. Low-sulfonate kraft lignin (LSL) and ethylcellulose (EC) were dissolved in a DMAc:THF mixture at different concentrations (8, 10, and 15 wt.%) and LSL:EC ratios (50:50, 70:30, and 90:10) and subjected to electrospinning. The resulting electrospun nanostructures were morphologically characterized. EC acting as the cospinning polymer improved both LSL spinnability and the oil structuring ability. Solutions with a high lignin content achieved microsized particles connected by fibrils, whereas solutions with a high EC content (50:50 ratio) and LSL/EC total concentration (10 and 15 wt.%) yielded beaded or bead-free nanofibers, due to enhanced extensional viscoelastic properties and nonNewtonian characteristics. The gel-like properties of electrospun nanostructure dispersions in castor oil were strengthened with the nanostructure concentration and the EC:LSL ratio, as a result of the formation of a more interconnected fiber network. The oleodispersions studied exhibited a satisfactory frictional response in a tribological contact, with friction coefficient values that were comparable to those achieved with traditional lithium-lubricating greases. Full article

The structure and flow behavior of lubricating greases depend on the base oil and the type and concentration of the dissolved thickener. In this study, the linear viscoelastic properties of greases were characterized by combining oscillatory shear and squeeze flow covering a broad frequency range (0.1–10⁵ rad s⁻¹). Multiple-particle tracking (MPT) microrheology and scanning electron microscopy (SEM) provided further insight into local viscoelastic properties and sample structure on a submicron-length scale. The type and viscosity of the base oil did not affect the absolute value of the complex viscosity and the filament shape formed by a given thickener. High-frequency shear modulus data, however, indicated that the thickener lithium 12-hydroxystearate formed stiffer networks/filaments in poly-α-olefins than in mineral oils. As expected, the viscosity increased with increased thickener concentrations, but microscopy and high-frequency rheometry revealed that the thickness, length, and stiffness of the individual filaments did not change. In mineral oil, the 12-hydroxystearate thickeners yielded higher viscosity than the corresponding stearates with the same metal ion. The filamentous lithium thickeners created stronger networks than the roundish aggregates formed by magnesium and zinc stearate. Network mesh sizes varying between approximately 100 nm and 300 nm were consistently determined from SEM image analysis and MPT experiments. The MPT experiments further disclosed the existence of gel-like precursors of approximately 130 µm at thickener concentrations far below the critical value at which a sample-spanning network resulting in a characteristic grease texture is formed. Full article

Both activated sludge/contact aeration (AS/CA) and AS-only systems for treating oil-containing domestic sewage were tested. The results of these tests indicate that the oil and grease removal ratios of the AS/CA system exceeded those of the AS-only system. When the influent oil and grease concentration reached 60 mg/L, the effluent concentration of the AS system was 13 mg/L, which exceed 10 mg/L, the Taiwan Effluent Standard for oil and grease. However, in the AS/CA system, the effluent oil and grease concentration was 8 mg/L, which was below the required standard. This study analyzes the biological phases of the AS-only system and the combined AS/CA system using a scanning electronic microscope and a denatured gradient gel electrophoresis method when the inflow concentration of oil and grease is increased to 120 mg/L. The results of the Chemical Oxygen Demand (COD) experiment reveal that the AS/CA system is affected less than the AS system, and the COD removal rate of the AS/CA system is maintained at 81%, which exceeds that (61.5%) of the AS-only system. The analytical results thus obtained suggest that both the amounts of biological phase and the biomass in the combined AS/CA system exceed those of an AS-only system. Full article

The main objective of this work was the incorporation of reactive isocyanate groups into chitin and chitosan in order to effectively use the products as reactive thickening agents in castor oil. The resulting gel-like dispersions could be potentially used as biodegradable lubricating greases. Three different NCO–functionalized polymers were obtained: two of them by promoting the reaction of chitosan with 1,6-hexamethylene diisocyanate (HMDI), and the other by using chitin instead of chitosan. These polymers were characterized through ¹H-NMR, FTIR and thermogravimetric analysis (TGA). Thermal and rheological behaviours of the oleogels prepared by dispersing these polymers in castor oil were studied by means of TGA and small-amplitude oscillatory shear (SAOS) measurements. The evolution and values of the linear viscoelasticity functions with frequency for –NCO–functionalized chitosan- and chitin-based oleogels are quite similar to those found for standard lubricating greases. In relation to long-term stability of these oleogels, no phase separation was observed and the values of viscoelastic functions increase significantly during the first seven days of ageing, and then remain almost constant. TGA analysis showed that the degradation temperature of the resulting oleogels is higher than that found for traditional lubricating greases. Full article