Lignin-enriched residues from bioethanol production: Chemical characterization, isocyanate functionalization and oil structuring properties.

Lignin-enriched waste products from bioethanol production of agriculture residues were tested as structuring agents in castor oil once functionalized with hexamethylene diisocyanate. Cane bagasse, barley and wheat straw were processed through steam explosion, pre-saccharification and simultaneous saccharification and fermentation (PSSF). Alternatively, cane bagasse was submitted to steam explosion and enzymatic hydrolysis (EH). Several Nuclear Magnetic Resonance techniques were used to characterize both residues and NCO-functionalized counterparts. The ß-O-4'/resinol/phenylcoumaran content and hydroxyphenyl/guaiacyl/syringyl distribution depend on biomass source, pretreatment, and enzymatic hydrolysis. Total hydroxyl content (from 1.23 for cane bagasse to 1.85 for wheat straw residues), aromatic/aliphatic hydroxyl ratio (0.78 for cane bagasse and 0.61 and 0.49 for barley and wheat straw residues, respectively) and S/G ratio (ranging from 0.25 to 0.86) influence the NCO-functionalization and oleogel rheological response. Oleogels obtained with barley straw residues exhibited the highest values of the storage modulus; around 2 × 105 Pa and 104 Pa for 25% and 20% contents, respectively. PSSF process showed weaker modification, leading to softer viscoelastic response compared to EH. These oleogels exhibited rheological properties similar to lubricating greases of different NLGI grades. Therefore, we herein show an integrative protocol for the valorization of lignin-enriched residues from bioethanol production as potential thickeners of lubricating greases.

Lubrication by Adsorption Films of Hydrophilic Amine-based Protic Ionic Liquids: Effect of Anion Species.

In this study, we synthesize hydrophilic amine-based protic ionic liquids (PILs) with hydroxy groups in a cation and different anions. Subsequently, we evaluate the kinetic friction coefficients of iron oxide in aqueous solutions of the PILs under different sliding conditions. Ditriethanolamine malate, triethanolamine lactate, triethanolamine methoxyacetate, and triethanolamine acetate are used as PIL samples in this study. Among them, ditriethanolamine malate exhibits the lowest kinetic friction coefficient. As the number of sliding cycles increases, the excellent lubrication capability remains. Subsequently, we characterize the adsorption of the PILs on an iron oxide surface to investigate the lubrication behavior on the basis of quartz crystal microbalance with dissipation monitoring and force curve data. We expect hydrophilic PILs to be excellent water-soluble lubricants and additives for use in metal surface treatments.

Critical Tools in Tableting Research: Using Compaction Simulator and Quality by Design (QbD) to Evaluate Lubricants' Effect in Direct Compressible Formulation.

As commonly known, the product development stage is quite complex, requires intensive knowledge, and is time-consuming. The selection of the excipients with the proper functionality and their corresponding levels is critical to drug product performance. The objective of this study was to apply quality by design (QbD) principles for formulation development and to define the desired product quality profile (QTPP) and critical quality attributes (CQA) of a product. QbD is a risk- and science-based holistic approach for upgraded pharmaceutical development. In this study, Ibuprofen DC 85W was used as a model drug, Cellactose® 80 along with MicroceLac® 100 as a filler, and magnesium stearate, stearic acid, and sodium stearyl fumarate as lubricants. By applying different formulation parameters to the filler and lubricants, the QbD approach furthers the understanding of the effect of critical formulation and process parameters on CQAs and the contribution to the overall quality of the drug product. An experimental design study was conducted to determine the changes of the obtained outputs of the formulations, which were evaluated using the Modde Pro 12.1 statistical computer program that enables optimization by modeling complex relationships. The results of the optimum formulation revealed that MicroceLac® 100 was the superior filler, while magnesium stearate at 1% was the optimum lubricant. A design space that indicates the safety operation limits for the process and formulation variables was also created. This study enriches the understanding of the effect of excipients in formulation and assists in enhancing formulation design using experimental design and mathematical modeling methods in the frame of the QbD approach.

Prospects and Challenges of Microwave-Combined Technology for Biodiesel and Biolubricant Production through a Transesterification: A Review.

Biodiesels and biolubricants are synthetic esters produced mainly via a transesterification of other esters from bio-based resources, such as plant-based oils or animal fats. Microwave heating has been used to enhance transesterification reaction by converting an electrical energy into a radiation, becoming part of the internal energy acquired by reactant molecules. This method leads to major energy savings and reduces the reaction time by at least 60% compared to a conventional heating via conduction and convection. However, the application of microwave heating technology alone still suffers from non-homogeneous electromagnetic field distribution, thermally unstable rising temperatures, and insufficient depth of microwave penetration, which reduces the mass transfer efficiency. The strategy of integrating multiple technologies for biodiesel and biolubricant production has gained a great deal of interest in applied chemistry. This review presents an advanced transesterification process that combines microwave heating with other technologies, namely an acoustic cavitation, a vacuum, ionic solvent, and a supercritical/subcritical approach to solve the limitations of the stand-alone microwave-assisted transesterification. The combined technologies allow for the improvement in the overall product yield and energy efficiency. This review provides insights into the broader prospects of microwave heating in the production of bio-based products.

Hybrid Nanocellulose-Copper (II) Oxide as Engine Oil Additives for Tribological Behavior Improvement.

Friction and wear are the main factors in the failure of the piston in automobile engines. The objective of this work was to improve the tribological behaviour and lubricant properties using hybrid Cellulose Nanocrystal (CNC) and Copper (II) oxide nanoparticles blended with SAE 40 as a base fluid. The two-step method was used in the hybrid nanofluid preparation. Three different concentrations were prepared in a range of 0.1% to 0.5%. Kinematic viscosity and viscosity index were also identified. The friction and wear behavior were evaluated using a tribometer based on ASTM G181. The CNC-CuO nano lubricant shows a significant improvement in term of viscosity index by 44.3-47.12% while for friction, the coefficient of friction (COF) decreases by 1.5%, respectively, during high and low-speed loads (boundary regime), and 30.95% during a high-speed, and low load (mixed regime). The wear morphologies results also show that a smoother surface was obtained after using CNC-CuO nano lubricant compared to SAE 40.

Bioinspired Hyaluronic Acid/Phosphorylcholine Polymer with Enhanced Lubrication and Anti-Inflammation.

Under pathological conditions, the joint is not well lubricated, which inevitably leads to osteoarthritis. Currently, in clinics injection of hyaluronic acid (HA) as an intra-articular viscosupplement is one of the main methods for alleviation of osteoarthritis. However, the viscosity of HA reduces dramatically under high shear rate due to the shear-thinning effect. Therefore, it is crucial to enhance the lubrication property of HA in order to treat osteoarthritis effectively. In this study, we successfully grafted 2-methacryloyloxyethyl phosphorylcholine (MPC), which is a zwitterionic biomaterial with excellent hydration lubrication, onto the HA with two different molecular weights (HAMPC) to enhance lubrication. The lubrication test performed using an atomic force microscope showed that, compared with HA, the friction coefficient of HAMPC was greatly reduced under various conditions. The in vitro test demonstrated that HAMPC was biocompatible and could upregulate cartilage anabolic genes while simultaneously downregulating cartilage catabolic proteases and pain-related genes. Importantly, high molecular weight HAMPC exhibited improved the capability to regulate these genes compared with low molecular weight HAMPC. In conclusion, the high molecular weight HAMPC developed herein, with enhanced lubrication and anti-inflammation, may be a promising polymer for the treatment of osteoarthritis.

Biomimetic Lubrication and Surface Interactions of Dopamine-Assisted Zwitterionic Polyelectrolyte Coatings.

A bioinspired zwitterionic polyelectrolyte coating with excellent hydration ability has been regarded as a promising lubricating candidate for modifying artificial joint cartilage surface. In physiological fluids, the ubiquitous proteins play an important role in achieving outstanding boundary lubrication; however, a comprehensive understanding of the hydration lubrication between polyelectrolyte coatings and proteins still remains unclear. In this work, a facile fabrication of ultrasmooth polyelectrolyte coatings was developed via codeposition of synthesized poly(dopamine methacrylamide- co-2-methacryloyloxyethyl phosphorylcholine) (P(DMA- co-MPC)) and dopamine (DA) in a mild condition. Upon optimization of the feeding ratio of P(DMA- co-MPC) and DA, the as-fabricated PDA/P(DMA- co-MPC) coatings exhibit excellent lubricating properties when sliding with each other (friction coefficient µ = 0.036 ± 0.002, ∼2.8 MPa), as well as sliding with a model protein (bovine serum albumin (BSA)) layer (µ = 0.041 ± 0.005, ∼4.8 MPa) in phosphate-buffered saline (PBS, pH 7.4). Intriguingly, the lubrication in both systems shows Amontons-like behaviors: the friction is directly proportional to the applied load but independent of the shear velocity. Moreover, the PDA/P(DMA- co-MPC) coatings could resist the protein fouling (i.e., BSA) in PBS, which is crucial to prevent the surfaces from being contaminated when applied in biological media, thus maintaining their lubricating properties. Our results provide a versatile approach for facilely fabricating polyelectrolyte coatings with superior lubrication properties to both polyelectrolyte coatings and protein surfaces, with useful implications into the development of novel lubricating coatings for bioengineering applications (e.g., artificial joints).

Synthesis, Characterization, and Performance Evaluation of Sulfur-Containing Diphenylamines Based on Intramolecular Synergism.

To obtain novel structural antioxidants that have different antioxidant mechanisms, four 2-(alkylthio)-N-(4-(phenylamino)phenyl)acetamides 2a-d as dual functional antioxidants are designed, synthesized, and confirmed by ¹H-NMR, FTIR, MS, and elemental analysis. The antioxidant behavior of compounds 2a-d as additives of base oil triisodecyl trimellitate (TIDTM) is evaluated by non-isothermal and isothermal DSC analyses. The results showed all compounds can greatly increase the incipient oxidation temperature (IOT) and oxidation induction time (OIT) of TIDTM, especially, compound 2c exhibited an OIT value of 72.5 min at 230 °C, which is almost 28 times the length of TIDTM. Moreover, compounds 2a-d do not affect the tribological performance of TIDTM. The mechanism of antioxidants involved an intramolecular synergism are proposed. This work demonstrates compound 2c can be used as a novel potential antioxidant additive of TIDTM; in addition, it would inspire the emergence of highly potent antioxidants with different antioxidant mechanisms.

Viscous Flow Behaviour of Karanja Oil Based Bio-lubricant Base Oil.

Karanja oil (KO) is widely used for synthesis of bio-fuel karanja oil methyl ester (KOME) due to its competitive price, good energy values and environmentally friendly combustion properties. Bio-lubricant is another value added product that can be synthesized from KO via chemical modification. In this work karanja oil trimethylolpropane ester (KOTMPE) bio-lubricant was synthesized and evaluated for its viscous flow behaviour. A comparison of viscous flow behaviours of natural KO and synthesized bio-fuel KOME and bio-lubricant KOTMPE was also made. The aim of this comparison was to validate the superiority of KOTMPE bio-lubricant over its precursors KO and KOME in terms of stable viscous flow at high temperature and high shear rate conditions usually encountered in engine operations and industrial processes. The free fatty acid (FFA) content of KO was 5.76%. KOME was synthesized from KO in a two-step, acid catalyzed esterification followed by base catalyzed transesterification, process at 65°C for 5 hours with oil-methanol ratio 1:6, catalysts H2SO4 and KOH (1 and 1.25% w/w KO, respectively). In the final step, KOTMPE was prepared from KOME via transesterification with trimethylolpropane (TMP) at 150°C for 3 hours with KOME-TMP ratio 4:1 and H2SO4 (2% w/w KOME) as catalyst. The viscosity versus temperature studies were made at 0-80°C temperatures in shear rate ranges of 10-1000 s-1 using a Discovery Hybrid Rheometer, model HR-3 (TA instruments, USA). The study found that viscosities of all three samples decreased with increase in temperature, though KOTMPE was able to maintain a good enough viscosity at elevated temperatures due to chemical modifications in its molecular structure. The viscosity index (VI) value for KOTMPE was 206.72. The study confirmed that the synthesized bio-lubricant KOTMPE can be used at high temperatures as a good lubricant, though some additives may be required to improve properties other than viscosity.

Cyclic Polymer Grafts That Lubricate and Protect Damaged Cartilage.

Tissue-reactive graft copolymers were designed to protect the cartilage against enzymatic degradation and restore its lubrication properties during the early stages of osteoarthritis (OA). The copolymers feature a poly(glutamic acid) (PGA) backbone bearing hydroxybenzaldehyde (HBA) functions and cyclic poly(2-methyl-2-oxazoline) (PMOXA) side chains. PGA-PMOXA-HBA species chemisorb on the degraded tissue via Schiff bases and expose the biopassive and lubricious PMOXA cyclic grafts at the interface. The smaller hydrodynamic radius by cyclic PMOXA side chains coupled to the intrinsic absence of chain ends generate denser and more lubricious films on cartilage when compared to those produced by copolymers bearing linear PMOXA. Topology effects demonstrate how the introduction of cyclic polymers within tissue-reactive copolymers substantially improve their tribological and biopassive properties, suggesting a plethora of possible applications for cyclic macromolecules in biomaterials formulations.

Synthesis of Renewable Lubricant Alkanes from Biomass-Derived Platform Chemicals.

The catalytic synthesis of liquid alkanes from renewable biomass has received tremendous attention in recent years. However, bio-based platform chemicals have not to date been exploited for the synthesis of highly branched lubricant alkanes, which are currently produced by hydrocracking and hydroisomerization of long-chain n-paraffins. A selective catalytic synthetic route has been developed for the production of highly branched C23 alkanes as lubricant base oil components from biomass-derived furfural and acetone through a sequential four-step process, including aldol condensation of furfural with acetone to produce a C13 double adduct, selective hydrogenation of the adduct to a C13 ketone, followed by a second condensation of the C13 ketone with furfural to generate a C23 aldol adduct, and finally hydrodeoxygenation to give highly branched C23 alkanes in 50.6 % overall yield from furfural. This work opens a general strategy for the synthesis of high-quality lubricant alkanes from renewable biomass.

Synthesis of Ricinoleic Acid Estolides by the Esterification of Ricinoleic Acids Using Functional Acid Ionic Liquids as Catalysts.

Estolides of ricinoleic acid (RA) have been used as lubricants and pigment dispersant in many industries. In this paper, functional acid ionic liquids (ILs) were firstly used as catalysts to prepare RA estolides by the esterification of RAs in solvent-free system. Different ILs were used as catalysts for the esterification. Effect of reaction variables (IL amount, reaction temperature and reaction time) on the esterification were also investigated and optimized using response surface methodology (RSM). Among all tested ILs, [BSO3HMIM]TS showed the best performance for the esterification. Arrhenius equation for the esterification was lnV0 =14.897-7558.7/T, and the activation energy (Ea) was 62.84 kJ/mol. A high degree of polymerization with an acid value of 48.0±2.5 mg KOH/g was achieved at the optimized conditions (IL load 12%, reaction temperature 140°C, and reaction time 12 h). The effect of reaction variables on the esterification decreased in the order of catalyst loading of IL > reaction temperature > reaction time.

Production of Biomass-Based Automotive Lubricants by Reductive Etherification.

Growing concern with the effects of CO2 emissions due to the combustion of petroleum-based transportation fuels has motivated the search for means to increase engine efficiency. The discovery of ethers with low viscosity presents an important opportunity to improve engine efficiency and fuel economy. We show here a strategy for the catalytic synthesis of such ethers by reductive etherification/O-alkylation of alcohols using building blocks that can be sourced from biomass. We find that long-chain branched ethers have several properties that make them superior lubricants to the mineral oil and synthetic base oils used today. These ethers provide a class of potentially renewable alternatives to conventional lubricants produced from petroleum and may contribute to the reduction of greenhouse gases associated with vehicle emissions.

Characterization of Synthesized and Commercial Forms of Magnesium Stearate Using Differential Scanning Calorimetry, Thermogravimetric Analysis, Powder X-Ray Diffraction, and Solid-State NMR Spectroscopy.

Magnesium stearate is the salt of a complex mixture of fatty acids, with the majority being stearate and palmitate. It has multiple crystalline forms and, potentially, an amorphous form. Magnesium stearate is used in the pharmaceutical manufacturing industry as a powder lubricant, and typically is added at low levels (∼1%) during the manufacturing process and blended for a relatively short time (∼5 min). Proper levels and mixing times are needed, as too short a mixing time or too small a quantity will result in improper lubrication, and too much can negatively impact dissolution rates. The complex mixture of multiple fatty acids and crystalline forms in magnesium stearate leads to variability between commercial sources, and switching between sources can impact both the amount of lubricant and mixing time needed for proper lubrication. In order to better understand the complex nature of magnesium stearate, a variety of analytical techniques were used to characterize both synthesized and commercial magnesium stearate samples. The results show that correlation among differential scanning calorimetry, thermogravimetric analysis, solid-state NMR spectroscopy, and other techniques provides a unique insight into the forms of magnesium stearate. Finally, the ability to monitor form changes of magnesium stearate in an intact tablet using solid-state NMR spectroscopy is shown.

Binding and lubrication of biomimetic boundary lubricants on articular cartilage.

The glycoprotein, lubricin, is the primary boundary lubricant of articular cartilage and has been shown to prevent cartilage damage after joint injury. In this study, a library of eight bottle-brush copolymers were synthesized to mimic the structure and function of lubricin. Polyethylene glycol (PEG) grafted onto a polyacrylic acid (pAA) core mimicked the hydrophilic mucin-like domain of lubricin, and a thiol terminus anchored the polymers to cartilage surfaces much like lubricin's C-terminus. These copolymers, abbreviated as pAA-g-PEG, rapidly bound to cartilage surfaces with binding time constants ranging from 20 to 39 min, and affected lubrication under boundary mode conditions with coefficients of friction ranging from 0.140 ± 0.024 to 0.248 ± 0.030. Binding and lubrication were highly correlated (r2 = 0.89-0.99), showing that boundary lubrication in this case strongly depends on the binding of the lubricant to the surface. Along with time-dependent and dose-dependent behavior, lubrication and binding of the lubricin-mimetics also depended on copolymer structural parameters including pAA backbone length, PEG side chain length, and PEG:AA brush density. Polymers with larger backbone sizes, brush sizes, or brush densities took longer to bind (p < 0.05). Six of the eight polymers reduced friction relative to denuded cartilage plugs (p < 0.05), suggesting their potential to lubricate and protect cartilage in vivo. In copolymers with shorter pAA backbones, increasing hydrodynamic size inhibited lubrication (p < 0.08), while the opposite was observed in copolymers with longer backbones (p < 0.05). These polymers show similar in vitro lubricating efficacy as recombinant lubricins and as such have potential for in vivo treatment of post-traumatic osteoarthritis. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:548-557, 2017.

Mussel-Inspired Anchoring of Polymer Loops That Provide Superior Surface Lubrication and Antifouling Properties.

We describe robustly anchored triblock copolymers that adopt loop conformations on surfaces and endow them with unprecedented lubricating and antifouling properties. The triblocks have two end blocks with catechol-anchoring groups and a looping poly(ethylene oxide) (PEO) midblock. The loops mediate strong steric repulsion between two mica surfaces. When sheared at constant speeds of ∼2.5 µm/s, the surfaces exhibit an extremely low friction coefficient of ∼0.002-0.004 without any signs of damage up to pressures of ∼2-3 MPa that are close to most biological bearing systems. Moreover, the polymer loops enhance inhibition of cell adhesion and proliferation compared to polymers in the random coil or brush conformations. These results demonstrate that strongly anchored polymer loops are effective for high lubrication and low cell adhesion and represent a promising candidate for the development of specialized high-performance biomedical coatings.

A Novel Methodology for the Synthesis of Acyloxy Castor Polyol Esters: Low Pour Point Lubricant Base Stocks.

Castor oil, a non-edible oil containing hydroxyl fatty acid, ricinoleic acid (89.3 %) was chemically modified employing a two step procedure. The first step involved acylation (C(2)-C(6) alkanoic anhydrides) of -OH functionality employing a green catalyst, Kieselguhr-G and solvent free medium. The catalyst after reaction was filtered and reused several times without loss in activity. The second step is esterification of acylated castor fatty acids with branched mono alcohol, 2-ethylhexanol and polyols namely neopentyl glycol (NPG), trimethylolpropane (TMP) and pentaerythritol (PE) to obtain 16 novel base stocks. The base stocks when evaluated for different lubricant properties have shown very low pour points (-30 to -45°C) and broad viscosity ranges 20.27 cSt to 370.73 cSt, higher viscosity indices (144-171), good thermal and oxidative stabilities, and high weld load capacities suitable for multi-range industrial applications such as hydraulic fluids, metal working fluids, gear oil, forging and aviation applications. The study revealed that acylated branched mono- and polyol esters rich in monounsaturation is desirable for developing low pour point base stocks.

Polyamine Triglycerides: Synthesis and Study of Their Potential in Lubrication, Neutralization, and Sequestration.

Renewable resources have evoked a new awakening in both scientific and industrial circles in the past decade. Vegetable oil is one category of renewables that is amenable as a source of new industrial products. Because the source feedstock, seeds, are environmentally friendly, the derivatized products from these at the end of their lifetime could also be benign when designed appropriately. Bioethanol and biodiesel are examples of biobased industrial products currently in the market place and have become resources for uplifting the rural economy. Biolubricants also are playing a more prominent role because they have become closely competitive with petroleum-based lubricants. These products are renewable because the crops from which the feedstuff for the biofuels and biolubricants are produced are grown annually in contrast to nonrenewable mineral sources. Added to their renewability is the inherent biodegradability of their end-use products after their useful lifetime. In a recent study of the lubricity characteristics of peracylated polyhydroxy milkweed oil, the derivatives were found to exhibit good oxidative stability as well as excellent antiwear properties. To further explore an expansion in the properties of such materials in lubrication and other applications, in this study the polyhydroxy (OH) moieties of derivatized milkweed triglycerides were replaced with -NHR groupings in the oil. In this process novel polyketo triglyceride intermediates leading to polyamine derivatives of the vegetable oil have been synthesized. The polyamine triglyceride markedly improved the stability of the parent oil to oxidative stress. It has also attenuated the extreme viscosity of the starting polyhydroxy oil to a more useful product that could be amenable for use as a lubricating agent, for example, hydraulic fluid. Both the polyketone and polyimine intermediates of the polyamine have chelating properties. The intermediates and the polyamine were characterized spectroscopically, tribologically, and rheologically for their intrinsic properties.

Preparation and properties evaluation of biolubricants derived from canola oil and canola biodiesel.

This study demonstrates the evaluation and comparison of the lubricity properties of the biolubricants prepared from the feed stocks such as canola oil and canola biodiesel. Biolubricant from canola biodiesel has a low cloud and pour point properties, better friction and antiwear properties, low phase transition temperature, is less viscous, and has the potential to substitute petroleum-based automotive lubricants. Biolubricant from canola oil has high thermal stability and is more viscous and more effective at higher temperature conditions. This study elucidates that both the biolubricants are attractive, renewable, and ecofriendly substitutes for the petroleum-based lubricants.

Bio-lubricants derived from waste cooking oil with improved oxidation stability and low-temperature properties.

Waste cooking oil (WCO) was chemically modified via epoxidation using H2O2 followed by transesterification with methanol and branched alcohols (isooctanol, isotridecanol and isooctadecanol) to produce bio-lubricants with improved oxidative stability and low temperature properties. Physicochemical properties of synthesized bio-lubricants such as pour point (PP), cloud point (CP), viscosity, viscosity index (VI), oxidative stability, and corrosion resistant property were determined according to standard methods. The synthesized bio-lubricants showed improved low temperature flow performances compared with WCO, which can be attributing to the introduction of branched chains in their molecular structures. What's more, the oxidation stability of the WCO showed more than 10 folds improvement due to the elimination of -C=C-bonds in the WCO molecule. Tribological performances of these bio-lubricants were also investigated using four-ball friction and wear tester. Experimental results showed that derivatives of WCO exhibited favorable physicochemical properties and tribological performances which making them good candidates in formulating eco-friendly lubricants.