A Short Review on Polymeric Biomaterials as Additives for Lubricants.

With increasing environmental concerns and the depletion of petroleum resources, the development of lubricant additives from bioresources has attracted much attention recently. In this review, we reported a few polymers and polymer composites that are synthesized from vegetable oils (soybean oil, sunflower oil, rice bran oil, and castor oil) and used as multifunctional additives in the formulation of eco-friendly lubricant compositions. We mentioned the preparation of vegetable oil-based homo- and copolymers and their characterization by different spectral techniques (FTIR/NMR). The average molecular weights of the polymers are determined by gel permeation chromatography (GPC). Performance evaluations of the polymeric materials mainly as a viscosity index improver (VII), pour point depressant (PPD), and most importantly antifriction additives when blended with lubricating base oils are indicated. Standard ASTM methods have been applied to evaluate their performances. The findings have shown that all the additives discussed are non-toxic, biodegradable, and showed excellent performances compared to commercial petroleum-based additives.

Evaluation of a sugar-based edible adhesive using a tensile strength tester.

A method to evaluate adhesives has been developed and used to reformulate a recently patented adhesive which is based on sugar and citric acid. Factors affecting adhesive performance were uncovered, such as an optimal curing temperature of 60°C. The addition of maltodextrin and soy protein at optimized levels was shown to nearly double the bonding strength of the adhesive, from 0.46 ± 0.076 to 0.74 ± 0.26 kN, under our test conditions. Also discussed is the potential for this method to be automated using commercially available equipment.

Synthesis of an amine-oleate derivative using an ionic liquid catalyst.

A facile (and environmentally friendly) reaction between epoxidized methyl oleate and aniline to produce an oleate-aniline adduct, without the formation of fatty amide, was discovered. This reaction was carried out neat, with a catalytic amount of an ionic liquid. No solvent was used, no byproducts were produced, and the ionic liquid could be recovered and recycled. The reaction products were fully characterized by NMR and GC-MS.

Lubricant base stock potential of chemically modified vegetable oils.

The environment must be protected against pollution caused by lubricants based on petroleum oils. The pollution problem is so severe that approximately 50% of all lubricants sold worldwide end up in the environment via volatility, spills, or total loss applications. This threat to the environment can be avoided by either preventing undesirable losses, reclaiming and recycling mineral oil lubricants, or using environmentally friendly lubricants. Vegetable oils are recognized as rapidly biodegradable and are thus promising candidates as base fluids in environment friendly lubricants. Lubricants based on vegetable oils display excellent tribological properties, high viscosity indices, and flash points. To compete with mineral-oil-based lubricants, some of their inherent disadvantages, such as poor oxidation and low-temperature stability, must be corrected. One way to address these problems is chemical modification of vegetable oils at the sites of unsaturation. After a one-step chemical modification, the chemically modified soybean oil derivatives were studied for thermo-oxidative stability using pressurized differential scanning calorimetry and a thin-film micro-oxidation test, low-temperature fluid properties using pour-point measurements, and friction-wear properties using four-ball and ball-on-disk configurations. The lubricants formulated with chemically modified soybean oil derivatives exhibit superior low-temperature flow properties, improved thermo-oxidative stability, and better friction and wear properties. The chemically modified soybean oil derivatives having diester substitution at the sites of unsaturation have potential in the formulation of industrial lubricants.

One-pot synthesis of chemically modified vegetable oils.

Vegetable oils are promising candidates as substitutes for petroleum base oils in lubricant applications, such as total loss lubrication, military applications, and outdoor activities. Although vegetable oils have some advantages, they also have poor oxidation and low temperature stability. One of the ways to address these issues is chemical modification of fatty acid chain of triglyceride. We report a one-pot synthesis of a novel class of chemically modified vegetable oils from epoxidized triacylglycerols and various anhydrides. In an anhydrous solvent, boron trifluoride etherate is used as catalyst to simultaneously open the oxirane ring and activate the anhydride. The reaction was monitored and products confirmed by NMR, FTIR, GPC, and TGA analysis. Experimental conditions were optimized for research quantity and laboratory scale-up (up to 4 lbs). The resultant acyl derivatives of vegetable oil, having diester substitution at the sites of unsaturation, have potential in formulation of industrial fluids such as hydraulic fluids, lubricants, and metal working fluids.

Ester hydroxy derivatives of methyl oleate: tribological, oxidation and low temperature properties.

Five branched oleochemicals were prepared from commercially available methyl oleate and common organic acids; and their lubricant properties were determined. These branched oleochemicals are characterized as 9(10)-hydroxy-10(9)-ester derivatives of methyl oleate. These derivatives show improved low temperature properties, over olefinic oleochemicals, as determined by pour point and cloud point measurements. The derivatization also increased thermo-oxidative stability, measured using both pressurized differential scanning calorimetry (PDSC) and thin film micro oxidation (TFMO) methods. Branched oleochemicals were used as additives both in soybean oil and in polyalphaolefin. Their lubrication enhancement was evaluated by both four-ball and ball-on-disk wear determinations. These derivatives have good anti-wear and friction-reducing properties at relatively low concentrations, under all test loads. Their surface tensions were also determined and a trend was observed. The materials with larger side chain branches had lower surface tension than those containing smaller side chain branches. An exception to this trend was found when studying the compound with the carbonyl containing levulinic acid side chain, which had the highest surface tension of the branched oleochemicals studied. Overall, the data indicate that some of these derivatives have significant potential as a lubricating oil or fuel additives.

From oligomers to molecular giants of soybean oil in supercritical carbon dioxide medium: 1. Preparation of polymers with lower molecular weight from soybean oil.

Polymers with a low molecular weight derived from soybean oil have been prepared in a supercritical carbon dioxide medium by cationic polymerization. Boron trifluoride diethyl etherate was used as an initiator. Influences of polymerization temperature, amount of initiator, and carbon dioxide pressure on the molecular weight were investigated. It is shown that the higher polymerization temperature favors polymers with relatively higher molecular weights. Larger amounts of initiator also provide polymers with higher molecular weights. Higher pressure favors polymers with relatively higher molecular weights. The applications of these soy-based materials will be in the lubrication and hydraulic fluid areas.

Biobased grease with improved oxidation performance for industrial application.

Vegetable oils have significant potential as a base fluid and a substitute for mineral oil for grease formulation. This paper describes the preparation of biobased grease with high oxidative stability and a composition useful for industrial, agriculture/farming equipment, and forestry applications. The process utilizes more oxidatively stable epoxy vegetable oils as the base fluid, metal-soap thickener, and several specialty chemicals identified to address specific applications. Performance characteristics of greases used for industrial and automotive applications are largely dependent on the hardness and the oxidative stability of grease. Grease hardness was determined using standard test methods, and their oxidative stabilities were determined using pressurized differential scanning calorimetry and rotary bomb oxidation tests. Wear data were generated using standard test methods in a four-ball test geometry. Results indicate that grease developed with this method can deliver at par or better performance properties (effective lubrication, wear protection, corrosion resistance, friction reduction, heat removal, etc.) than existing mineral oil-based greases currently used in similar trades. Therefore, developed greases can be a good substitute for mineral oil-based greases in industrial, agriculture, forestry, and marine applications.

A new polymer-lipid hybrid nanoparticle system increases cytotoxicity of doxorubicin against multidrug-resistant human breast cancer cells.

PURPOSE: This work is intended to develop and evaluate a new polymer-lipid hybrid nanoparticle system that can efficiently load and release water-soluble anticancer drug doxorubicin hydrochloride (Dox) and enhance Dox toxicity against multidrug-resistant (MDR) cancer cells. METHODS: Cationic Dox was complexed with a new soybean-oil-based anionic polymer and dispersed together with a lipid in water to form Dox-loaded solid lipid nanoparticles (Dox-SLNs). Drug loading and release properties were measured spectrophotometrically. The in vitro cytotoxicity of Dox-SLN and the excipients in an MDR human breast cancer cell line (MDA435/LCC6/MDR1) and its wild-type line were evaluated by trypan blue exclusion and clonogenic assays. Cellular uptake and retention of Dox were determined with a microplate fluorometer. RESULTS: Dox-SLNs were prepared with a drug encapsulation efficiency of 60-80% and a particle size range of 80-350 nm. About 50% of the loaded drug was released in the first few hours and an additional 10-20% in 2 weeks. Treatment of the MDR cells with Dox-SLN resulted in over 8-fold increase in cell kill when compared to Dox solution treatment at equivalent doses. The blank SLN and the excipients exhibited little cytotoxicity. The biological activity of the released Dox remained unchanged from fresh, free Dox. Cellular Dox uptake and retention by the MDR cells were both significantly enhanced (p < 0.05) when Dox was delivered in Dox-SLN form. CONCLUSIONS: The new polymer-lipid hybrid nanoparticle system is effective for delivery of Dox and enhances its efficacy against MDR breast cancer cells.

"Green" composites from renewable resources: preparation of epoxidized soybean oil and flax fiber composites.

In recent years there has been considerable interest in using natural plant fibers as reinforcements for plastics. The motivation includes cost, performance enhancement, weight reduction, and environment concerns. High performance flax fiber could potentially substitute for glass or carbon fibers as reinforcements for plastics. This study reports the "green" composites obtained from a mixture of epoxidized soybean oil and epoxy resin, 1,1,1-tris(p-hydroxyphenyl)ethane triglycidyl ether (THPE-GE), reinforced with flax fiber. The compression molding method is used for making the composites. Curing agents triethylenetetramine and diethylenetriamine provide better physical properties of the composites than Jeffamine agents D-230 and EDR-148. Both the flexural modulus and the tensile modulus of the composites increase as the amount of THPE-GE increases. The flexural modulus increased at a fiber content of <10 wt %, but there is a decrease beyond 10 wt %. The tensile modulus increases with fiber content until a maximum at 13.5 wt %, and then it decreases. The flax fiber length affected the mechanical properties of the composites: the longer the fiber length, the better are the mechanical properties observed.

Synthesis of diethylamine-functionalized soybean oil.

Specialty chemicals based on renewable resources are desirable commodities due to their eco-friendly nature and "green" product characteristics. These chemicals can demonstrate physical and chemical properties comparable to those of conventional petroleum-based products. Suitably functionalized amines in the triacylglycerol structure can function as an antioxidant, as well as an antiwear/antifriction agent. In addition, the amphiphilic nature of seed oils makes them an excellent candidate as base fluid. The reaction of amine and epoxidized seed oils in the presence of a catalyst almost always leads to different intra/intermolecular cross-linked products. In most cases, the triacylglycerol structure is lost due to disruption of the ester linkage. Currently, there is no reported literature describing the aminolysis of vegetable oil without cross-linking. Here the epoxy group of the epoxidized soybean oil has been selectively reacted with amines to give amine-functionalized soybean oil. The optimization procedure involved various amines and catalysts for maximum aminolysis, without cross-linking and disruption of the ester linkage. Diethylamine and ZnCl2 were found to be the best. NMR, IR, and nitrogen analysis were used to characterize the products.

Synthesis of carbonated fatty methyl esters using supercritical carbon dioxide.

The two-step syntheses of the cyclic carbonates carbonated methyl oleate (CMO) and carbonated methyl linoleate (CML) are reported. First, synthesis of epoxides through well-precedented chemical reactions of unsaturated fatty methyl esters with hydrogen peroxide and formic acid was accomplished. Next, a carbonation reaction with a simple tetrabutylammonium bromide catalyst was performed, allowing the direct incorporation of carbon dioxide into the oleochemical. These syntheses avoid the use of the environmentally unfriendly phosgene. The carbonated products are characterized by IR, 1H NMR, and 13C NMR spectroscopy and studied by thermogravimetric analysis (TGA). Also reported is the synthesis of a similar cyclic carbonate from the commercially available 2-ethylhexyl epoxy soyate. These carbonates show properties that may make them useful as petrochemical replacements or as biobased industrial product precursors.

Soybean oil based greases: influence of composition on thermo-oxidative and tribochemical behavior.

The biodegradable properties and lubricating ability of greases depend on both the base oil and the thickener. Mineral oils are the most widely used lubricant base fluids due to their inherent lubricity and low cost, but recent environmental awareness has forced consideration of the use of biodegradable fluids such as vegetable oils and certain synthetic fluids in grease formulations. This study presents data on the thermo-oxidation behavior and tribology of biodegradable greases formulated with soybean oil and different compositions of metal soap thickener. The composition of thickener has been varied by using fatty acids with different degrees of unsaturation and fatty acids of different chain lengths. The improvement of thermo-oxidation and tribological properties as a result of changing thickener/base oil ratio and the antioxidative effect of some suitable additives have also been evaluated.

Preparation of soybean oil-based greases: effect of composition and structure on physical properties.

Vegetable oils have significant potential as a base fluid and a substitute for mineral oil in grease formulation. Preparation of soybean oil-based lithium greases using a variety of fatty acids in the soap structure is discussed in this paper. Soy greases with lithium-fatty acid soap having C12-C18 chain lengths and different metal to fatty acid ratios were synthesized. Grease hardness was determined using a standard test method, and their oxidative stabilities were measured using pressurized differential scanning calorimetry. Results indicate that lithium soap composition, fatty acid types, and base oil content significantly affect grease hardness and oxidative stability. Lithium soaps prepared with short-chain fatty acids resulted in softer grease. Oxidative stability and other performance properties will deteriorate if oil is released from the grease matrix due to overloading of soap with base oil. Performance characteristics are largely dependent on the hardness and oxidative stability of grease used as industrial and automotive lubricant. Therefore, this paper discusses the preparation methods, optimization of soap components, and antioxidant additive for making soy-based grease.