Dilinoleic Acid Research Articles

Amended Safety Assessment of Dialkyl Dimer Dilinoleates as Used in Cosmetics.

The Expert Panel for Cosmetic Ingredient Safety (Panel) reassessed the safety of 8 dialkyl dimer dilinoleates as used in cosmetics. These ingredients are diesters formed from the reaction of straight-chained or branched alkyl alcohols and dilinoleic acid; these ingredients are reported to function in cosmetics as skin-conditioning agents. The Panel reviewed data relevant to the safety of these ingredients and concluded that Diisopropyl Dimer Dilinoleate, Dicetearyl Dimer Dilinoleate, Diisostearyl Dimer Dilinoleate, Diethylhexyl Dimer Dilinoleate, Dioctyldodecyl Dimer Dilinoleate, Ditridecyl Dimer Dilinoleate, Di-C16-18 Alkyl Dimer Dilinoleate, and Di-C20-40 Alkyl Dimer Dilinoleate are safe in cosmetics in the present practices of use and concentration described in this safety assessment.

Structure‐guided preparation of fuctional oil rich in 1,3‐diacylglycerols and linoleic acid from Camellia oil by combi‐lipase

Diacylglycerol (DAG)-enriched oil has been attracting attention because of its nutritional benefits and biological functions, although the composition of its various free fatty acids (FFAs) and an unclear relationship between substrate and yield make it difficult to be identified and qualified with respect to its production. In the present study, linoleic acid-enriched diacylglycerol (LA-DAG) was synthesized and enriched from Camellia oil by the esterification process using the combi-lipase Lipozyme TL IM/RM IM system. The relationship between FFA composition and DAG species productivity was revealed. The results showed that heterogeneous FFA with a major constituent (more than 50%) exhibited higher DAG productivity and inhibited triacylglycerol productivity compared to homogeneous constituents. Joint characterization by high-performance liquid chromatography-evaporative light scattering detection, gas chromatography-mass spectrometry and ultra-performance liquid chromatography-heated electrospray ionization-tandem mass spectrometry identified that DAG components contained dilinoleic acid acyl glyceride, linoleyl-oleyl glyceride and dioleic acid acyl glyceride in esterification products. Under the optimum conditions, 60.4% 1,3-DAG and 61.3% LA-DAG in the crude product at 1h reaction were obtained, and further purified to 81.7% LA-DAG and 94.7% DAG via silica column chromatography. The present study provides a guideline for the identification of DAG species, as well as a structure-guided preparation method of DAG-enriched oils via the cost-effective combi-lipase. © 2022 Society of Chemical Industry.

In Vivo Biocompatibility of an Innovative Elastomer for Heart Assist Devices.

Cardiac surgical approaches require the development of new materials regardless of the polyurethanes used for pulsatile blood pumps; therefore, an innovative biomaterial, a copolymer of poly(ethylene terephthalate) and dimer fatty acid (dilinoleic acid) modified with D-glucitol, hereafter referred to as PET/DLA, has been developed, showing non-hemolytic and atrombogenic properties and resistance to biodegradation. The aim of this work was to evaluate in vivo inflammatory responses to intramuscular implantation of PET/DLA biomaterials of different compositions (hard to soft segments). Two copolymers containing 70 and 65 wt.% of hard segments, as in poly(ethylene terephthalate) and dilinoleic acid in soft segments modified with D-glucitol, were used for implantation tests to monitor tissue response. Medical grade polyurethanes Bionate II 90A and Bionate II 55 were used as reference materials. After euthanasia of animals (New Zealand White rabbits, n = 49), internal organs and tissues that contacted the material were collected for histopathological examination. The following parameters were determined: peripheral blood count, blood smear with May Grunwald–Giemsa staining, and serum C-reactive protein (CRPP). The healing process observed at the implantation site of the new materials after 12 weeks indicated normal progressive collagenization of the scar, with an indication of the inflammatory–resorptive process. The analysis of the chemical structure of explants 12 weeks after implantation showed good stability of the tested copolymers in contact with living tissues. Overall, the obtained results indicate great potential for PET/DLA in medical applications; however, final verification of its applicability as a structural material in prostheses is needed.

Biofunctional catheter coatings based on chitosan-fatty acids derivatives

Multifunctional and biofunctional coatings for medical devices are an attractive strategy towards tailoring the interactions of the device with the body, thereby influencing the host response, and the susceptibility to microbial colonization. Here we describe the development of a coating process to yield amphiphilic, lubricious coatings, resistant to bacterial colonization, based on chitosan. Chitosan-fatty acid derivatives were obtained by simultaneous N,O-acylation of chitosan with either linoleic, α-linolenic, or dilinoleic acid. Chemical characterization of new materials was carried out using 1H NMR, FTIR, and XPS. Surface properties of coated polyester samples were studied using SEM and contact angle measurements, which indicated that the incorporation of hydrophobic constituents into chitosan macromolecules led to a decrease of both surface roughness and water contact angle. Importantly, tribological testing demonstrated that these new coatings decrease the coefficient of friction due to the self-organization of fatty acid (from 0.53 for the neat chitosan to 0.35 for chitosan-fatty acid derivative). Meanwhile, preliminary bacterial colonization tests indicated significant—over 80%—reduction in E. coli colonization following coating with chitosan-linoleic and chitosan-α-linolenic derivatives. Finally, cytotoxicity and hemocompatibility studies confirmed that all amphiphilic chitosan-fatty acid derivatives were non-toxic and non-hemolytic. Collectively, our results demonstrate the potential of the developed coating strategy, particularly the chitosan-linoleic and chitosan-α-linolenic acid derivatives, for applications as biofunctional catheter coatings.

Modification of Bacterial Cellulose with Quaternary Ammonium Compounds Based on Fatty Acids and Amino Acids and the Effect on Antimicrobial Activity

In the present work, bacterial cellulose (BC) membranes have been modified with bioactive compounds based on long chain dimer of C18 linoleic acid, referred to as the dilinoleic acid (DLA) and tyrosine (Tyr), a natural amino acid capable of forming noncovalent cation-π interactions with positively charged ethylene diamine (EDA). This new compound, [EDA][DLA-Tyr], has been synthesized by simple coupling reaction, and its chemical structure was characterized by 1H NMR and Fourier transform infrared spectroscopy. The antimicrobial activity of a new compound against S. aureus and S. epidermidis, two cocci associated with skin and wound infections, was assessed. The [EDA][DLA-Tyr] impregnated BC exhibited strong and long-term antimicrobial activity against both staphylococcal species. The results showed a 57-66% and 56-60% reduction in S. aureus and S. epidermidis viability, respectively, depending on [EDA][DLA-Tyr] concentration used. Importantly, [EDA][DLA-Tyr] molecules were released gradually from the BC pellicle, while a reference antibiotic, erythromycine (ER), did not show any antibacterial activity against S. aureus and S. epidermidis after 48 h of soaking in deionized water. Thus, a combination of [EDA][DLA-Tyr] and BC could be a promising new class of wound dressing displaying both biocompatibility and antimicrobial activity.

Enzymatically catalyzed poly(butylene succinate)(PBS) copolymers as building blocks for degradable scaffolds

Event Abstract Back to Event Enzymatically catalyzed poly(butylene succinate)(PBS) copolymers as building blocks for degradable scaffolds Miroslawa El Fray1, Monika Malesa1 and Aleksandra Kaczmarek1 1 West Pomeranian University of Technology Szczecin, Biomaterials and Microbiological Technologies, Poland Introduction: An increasing exploitation of regenerative potential of living tissues is observed from last two decades since temporary, biodegradable polymeric templates (scaffolds) are being developed for tissue engineering[1]. Biodegradable polymers are synthesized from non-toxic monomers, but toxic catalysts are frequently used like in case of biodegradable aliphatic polyesters where highly toxic tin compounds are used[2]. Therefore, stiff but biodegradable polymers are needed for tissue engineering and other biomedical applications. In our work we focus on much safer enzymatic biocatalysts which are proposed for the synthesis of aliphatic polyester, poly(butylene succinate)(PBS) and its copolymers. Materials and Methods: Poly(butylene succinate)(PBS) and its copolymers containing ethylene glycol sequences (PBS-EG) and dilinoleic acid sequences (PBS-DLA) were prepared by enzymatic polymerization of succinic acid ester (diethyl succinate)(DES), 1,4-butanediol (1,4-BD) and poly(ethylene glycol) (PEG_3000) or dilinoleic acid (DLA) in organic solvent (diphenyl ether). Lipase B derived from Candida antarctica strain, trade name Novozym 435th (N435), was used as a catalyst. The hard segments (PBS) to soft segments (EG or DLA) ratio based on stoichiometric calculations was 50:50 wt%. The reaction mixture was dissolved in chloroform to remove the unreacted monomers and impurities and then the microspheres in which the enzyme catalyst was immobilized were separated. Samples chemical structure were assessed by using ATR-FTIR and NMR analysis, degradation and contact angle measurement. Sample mechanical characterization was performed by tensile test. Preliminary cell viability tests have been performed by using fibroblasts. Results and Discussion: The PBS-EG and PBS-DLA copolymers were synthesized using Candida Antarctica from lipase B. Analysis of chemical structure with 1H NMR and ATR FT-IR spectroscopy confirmed the presence of specific bonds and groups, characteristic for ester and ether groups. The contact angle measurements on both materials revealed differences in hydrophilicity thus indicating that depending from the nature of copolymer building block, degradation profile can be adjusted. This can be achieved along with mechanical properties changes since PBS-DLA copolymer showed to be more flexible as compared to PBS-EG. Positive results from the preliminary cell viability tests have been also obtained. Conclusions: Enzymatically catalyzed copolymers of poly(butylene succinate), namely PBS-EG and PBS-DLA has been obtained. Results showed that these materials have different surface and mechanical properties depending from the chemical structure of soft segment building block. Their degradation profile and mechanical properties can also be adjusted thus making them an interesting candidate for degradable scaffolds, specifically for heart tissue engineering. This work was supported by the National Science Centre under the HARMONIA scheme (UMO-2014/14/M/ST8/00610).

Friction behaviour of hydrophilic lubricious coatings for medical device applications

The friction behaviour of new chitosan derivative coatings obtained by chemical modification of chitosan with fatty acids (linoleic and dilinoleic acid) has been investigated in order to explore their potential as endovascular catheter coatings and to benchmark them against commercially available coatings used in endovascular catheter applications. An in vitro tribological system was developed that was intended to represent to a limited extent the in vivo tribological conditions of a typical endovascular catheterization procedure. Continuous reciprocating sliding tests were carried out with uncoated and coated polymer specimens. The results showed that all of the coatings tested decreased the coefficient of friction compared to the uncoated polymer. Compared to a neat chitosan coating, the chitosan derivative coatings showed a clear reduction in the coefficient of friction to levels similar to those of the commercially-available coatings. A comparison between the friction results and contact angle measurements carried out on the coatings indicated that a range of contact angle values exists for which the friction coefficient is at a minimum. The reason for this is unclear and further studies are required in order to confirm and investigate the trend, especially within the context of hydrophilic lubricious coating development.

The effect of catalyst and segmental composition on the crystallization of multiblock polyesters for biomedical applications

In the present work, segmented thermoplastic elastomers (TPE) containing hard segments of poly(ethylene terephthalate) (PET) and soft segments comprising amorphous fatty acid ester sequences based on dilinoleic acid (DLA) were synthesized. The aim was to obtain transparent materials with high strength and flexibility. Thermal properties of the obtained PET/DLA copolymers were examined using differential scanning calorimetry (DSC). It was found that segmental composition and new type of catalyst used for the synthesis of PET/DLA copolymers has influence on materials transparency.

Nanocomposite Elastomeric Biomaterials for Myocardial Tissue Engineering Using Embryonic Stem Cell‐derived Cardiomyocytes

AbstractRegeneration or repair of the damaged myocardium requires different strategies including engineered constructs for more efficient cell delivery. This study was undertaken to examine the potential of a new nanostructured elastomer to deliver embryonic stem cell‐derived cardiomyocytes (ESC‐CM) to an infarcted area of the myocardium. Engineered materials were biocompatible, mechanically stable, and elastomeric nanocomposites serving as substrates for delivery of ESC‐CM and as a left ventricular support device in myocardial regeneration strategies. Materials investigated were soft and strong poly(aliphatic/aromatic‐ester) multiblock thermoplastic elastomers with poly(ethylene terephthalate) (PET) hard segments and dimerized fatty acid, i.e., dilinoleic acid (DLA) soft segments, respectively, with and without addition of 0.2 wt% TiO2 nanoparticles to form nanocomposites. The PET/DLA‐TiO2 nanocomposite exhibited over 8 MPa tensile strength and 900% elongation at break. Addition of TiO2 nanoparticles significantly altered surface roughness and enhanced adhesion and spreading of ESC‐CM derived from mouse and human embryonic stem cells. The newly developed materials did not affect the functional activity of spontaneously beating hESC‐CM, as demonstrated by unaltered rate of their beating, and the cells continued to demonstrate contractile activity on the materials for more than two months in culture (the longest time tested). Quantitative proliferation and survival assays using fibroblasts confirmed the ability of the new materials to support cells as well as or better than the present commercial‐type thermoplastic elastomer analog. The results indicate that PET/DLA and PET/DLA‐TiO2 are promising candidates for the manufacture of engineered patches to deliver ESC‐CMs.

Influence of soft segments on thermal and mechanical properties of terpoly(ester-ether-ester)s

The aim of the work was preparation and investigation of new multiblock terpoly(ester-ether-ester)s (TEEE) containing phthalic acid units as in poly(butylene terephthalate) (PBT) (hard segments) and hydrogenated dimer of dilinoleic acid called as dilinoleic acid sequences (DLA) as hydrophobic ester soft segments, and poly(ethylene glycol) (PEG) as hydrophilic ether soft segments. PEG of different molecular weight (1000 and 4600) was used. Synthesis was performed in a presence of α-tocopherol as non-toxic thermal stabilizer since these materials are targeted for biomedical applications. In this paper, the influence of amount and molecular weight of PEG on thermal and mechanical properties of TEEE is discussed.

Inhibition of calcification of polymer–ceramic composites incorporating nanocrystalline TiO2

An emerging problem related to the development of polymer surfaces resistant to calcification was addressed in this work. Multiblock copolymers containing poly(ethylene terephthalate) (PET) (30 wt-%) as hard segment and dilinoleic acid (DLA) as soft segment were prepared in the presence of two concentrations of TiO2 particles (23 nm diameter) as nanofiller (0˙2 and 0˙4 wt-%) via in situ polycondensation process. Changes of thermal properties as well as investigations of topography of these nanocomposites suggest that addition of small amount of TiO2 nanoparticles resulted in higher crystallinity and roughness of the copolymer surface. Incubation in simulated body fluid (SBF) increased the roughness of all copolymers characterised by root mean square (rms) values; however, no hydroxyapatite layer was formed on the samples surface. The highest difference of rms values was found for the neat PET/DLA material. The addition of nanocrystalline TiO2 seems to prevent the material surface from calcification which represents a positive effect when such nanocomposite is intended for medical applications, especially for uses in contact with soft tissue.

Formowanie wlokien z terpoli(estro-etero-estrow) metoda przedzenia ze stopu lub elektroprzedzenia z roztworu

Novel terpoly(ester-ether-ester)s (TEEE) built of hard segments, formed by poly(butylene terephthalate) (PBT), and soft blocks built of dilinoleic acid (DLA) residues and poly(ethylene glycol) (PEG) of different molecular weights (Table 1) were prepared. The fibers were prepared from the materials obtained using the methods of melt spinning or electrospinning from the solution (Fig. 1 and 5). The effects of PEG molecular weight and addition of organic thermal stabilizer (a-tocopherol, VE) as well as of addition of inorganic modifier (hydroxyapatite, HAP) on melt flow rate (MFR) (Fig. 2) and on mechanical (Fig. 3) and fiber-forming properties of TEEE were studied. Hybrid microfibers were prepared by melt spinning from the system containing HAP nanocrystalline ceramics. It was found that this ceramics thermally stabilized the material similarly as VE did. Terpolymers prepared from PEG of higher molecular weight (PEG 4600 ) showed very good mechanical properties and fibers prepared exhibited excellent elastic properties (high values of elastic recovery, Table 2).

Poly(ethylene terephthalate) modification with the monomer from renewable resources (in English)

An emerging problem related to the development of biodegradable polymers from renewable resources was brought up in this work. Modification of petrochemical-based poly(ethylene terephthalate)(PET) with the use of bio-based monomer, namely dilinoleic acid (DLA) was presented. Series of multiblock copolymers containing oligo-PET as hard segments and DLA as soft segments was obtained in typical process of PET synthesis via polycondensation from the melt. PET/DLA copolymers containing Wh=30-90 wt.% of hard segments were characterized with respect to their mechanical, thermal and processing properties. It was demonstrated that at high concentration of DLA (Wh=30-40 wt.%) materials are susceptible to hydrolytic degradation.

Final Report on the Amended Safety Assessment of Diisopropyl Dimer Dilinoleate, Dicetearyl Dimer Dilinoleate, Diisostearyl Dimer Dilinoleate, Dioctyl Dimer Dilinoleate, Dioctyldodecyl Dimer Dilinoleate, and Ditridecyl Dimer Dilinoleate

Diisopropyl Dimer Dilinoleate, Dicetearyl Dimer Dilinoleate, Diisostearyl Dimer Dilinoleate, Dioctyl Dimer Dilinoleate, Dioctyldodecyl Dimer Dilinoleate, and Ditridecyl Dimer Dilinoleate are diesters of their respective alcohols and dilinoleic acid. They function as skin-conditioning agents in a variety of cosmetic products at concentrations around 10%, but may be used at concentrations up to 53% in lipsticks. These ingredients do not absorb radiation in the ultraviolet (UV) UVA or UVB range and the only impurities expected are <0.5% dilinoleic acid, <0.1% isopropyl alcohol or <1% isostearyl alcohol, and/or small amounts of dilinoleic acid and cetearyl alcohol or octyldodecanol, depending on which diester is used. The potential skin penetration of these ingredients was evaluated using an estimate of the octanol/water partition coefficient (logP of 17.7) based on the structure of Diisopropyl Dimer Dilinoleate. This is consistent with the insolubility of these ingredients in water. Safety test data on dilinoleic acid (no adverse effects) were considered relevant because dilinoleic acid is a component of these diesters and a likely breakdown product. The acute oral and dermal LD(50) values for rats of Diisopropyl, Diisostearyl, and Dioctyldodecyl Dimer Dilinoleate were >5.0 g/kg. In a subchronic feeding study, macrophage aggregation was seen in the mesenteric lymph node at the lowest dose level (0.1% in the diet). These ingredients did not produce skin or ocular irritation in animal tests, nor were they comedogenic. Ames testing, clastogenesis in human lymphocytes in culture, and L5178Y mouse lymphoma cell forward mutations were all negative, indicating no dilinoleic acid genotoxicity. No carcinogenicity or reproductive/developmental toxicity data were available; however, structural alerts that would suggest a mutagenic or carcinogenic risk are absent. Significant reproductive/developmental toxicity or other systemic toxicity is not expected with these ingredients because they remain on the skin surface. In clinical studies, cosmetic formulations containing these ingredients did not produce skin irritation or sensitization, although one report of sensitization to dilinoleic acid appeared in the case literature. The Panel did note that the concentration of use of Diisopropyl Dimer Dilinoleate was reportedly as high as 53% in lipsticks, but that the highest concentration tested for irritation/sensitization is 27%. Given the size of these molecules, their relative insolubility in water, their lipophilic nature, and the absence of any significant case reports of allergic reactions, a use concentration of 53% is not likely to be associated with any adverse effects. Accordingly, these diesters were considered safe as used in cosmetic products.

Final Report on the Amended Safety Assessment of Diisopropyl Dimer Dilinoleate, Dicetearyl Dimer Dilinoleate, Diisostearyl Dimer Dilinoleate, Dioctyl Dimer Dilinoleate, Dioctyldodecyl Dimer Dilinoleate, and Ditridecyl Dimer Dilinoleate

Diisopropyl Dimer Dilinoleate, Dicetearyl Dimer Dilinoleate, Diisostearyl Dimer Dilinoleate, Dioctyl Dimer Dilinoleate, Dioctyldodecyl Dimer Dilinoleate, and Ditridecyl Dimer Dilinoleate are diesters of their respective alcohols and dilinoleic acid. They function as skin-conditioning agents in a variety of cosmetic products at concentrations around 10%, but may be used at concentrations up to 53% in lipsticks. These ingredients do not absorb radiation in the ultraviolet (UV) UVA or UVB range and the only impurities expected are &lt;0.5% dilinoleic acid, &lt;0.1% isopropyl alcohol or &lt;1% isostearyl alcohol, and/or small amounts of dilinoleic acid and cetearyl alcohol or octyldodecanol, depending on which diester is used. The potential skin penetration of these ingredients was evaluated using an estimate of the octanol/water partition coefficient (logP of 17.7) based on the structure of Diisopropyl Dimer Dilinoleate. This is consistent with the insolubility of these ingredients in water. Safety test data on dilinoleic acid (no adverse effects) were considered relevant because dilinoleic acid is a component of these diesters and a likely breakdown product. The acute oral and dermal LD50 values for rats of Diisopropyl, Diisostearyl, and Dioctyldodecyl Dimer Dilinoleate were &gt;5.0 g/kg. In a subchronic feeding study, macrophage aggregation was seen in the mesenteric lymph node at the lowest dose level (0.1% in the diet). These ingredients did not produce skin or ocular irritation in animal tests, nor were they comedogenic. Ames testing, clastogenesis in human lymphocytes in culture, and L5178Y mouse lymphoma cell forward mutations were all negative, indicating no dilinoleic acid genotoxicity. No carcinogenicity or reproductive/developmental toxicity data were available; however, structural alerts that would suggest a mutagenic or carcinogenic risk are absent. Significant reproductive/developmental toxicity or other systemic toxicity is not expected with these ingredients because they remain on the skin surface. In clinical studies, cosmetic formulations containing these ingredients did not produce skin irritation or sensitization, although one report of sensitization to dilinoleic acid appeared in the case literature. The Panel did note that the concentration of use of Diisopropyl Dimer Dilinoleate was reportedly as high as 53% in lipsticks, but that the highest concentration tested for irritation/sensitization is 27%. Given the size of these molecules, their relative insolubility in water, their lipophilic nature, and the absence of any significant case reports of allergic reactions, a use concentration of 53% is not likely to be associated with any adverse effects. Accordingly, these diesters were considered safe as used in cosmetic products.

Oleo chemicals as additives in paints and varnishes, etc: Part 2

Gelation that can occur when copper or aluminium bronze powder is permitted to stand in nitrocellulose lacquer can be prevented by the addition of below one percent of lauric acid. Butyl acetyl ricinoleate will impart highgloss, plasticity, pliability to nitro‐cellulose lacquers and impart permanence, and improves the ageing properties and low temperature flexibility to the product. Acrylic coatings of improved gloss and pattern control have been provided by the addition of methyl hydroxystearate. When barium α‐sulphostearate is added to interior or exterior paints it can produce films of improved hardness. Methyl linoleate can be employed to retard the hardening of Japanese film lacquer. Compositions with good heat stability and good thixotropic properties and which are suitable for use as a base for paints have been evolved by reacting hydrogenated castor oil with toluene di‐isocyanate and emulsifiable and polyethylene wax. The use of aluminium stearate in paints at elevated temperatures can result in films of high opacity, good build, sag resistance, heavy pigmented tolerance and good sealing properties. Myristic acid‐based alkyd aryl ketones have been utilised to impart lustre to wooden surfaces, and stearic acid terminated polyamide/polyimide for coatings for electrical insulators of magnetic wire have been applied to give improved lustre. Diethylene glycol esters of dilinoleic acid can be used to produce non‐drip paints, as can ethylene diamine bis hydroxystearate, and glyceryl trihydroxystearate. Hydrogenated castor oil is useable in the making of thixotropic agents applicable to paints have been prepared from the material, plus oligomers of hydroxystearic acid/ethylenediamine/sebacic acid polymers. Ethyl linoleate and ethyl linoleate have been used as penetrants in anti‐corrosive paints based upon alkyd resins. Aluminium stearate can prevent excess penetration by paints of surfaces. Bis (hydroxymethyl) propanediol oleate has found use in alkyd resins derivative coatings with butylated melamine resins‐hardening materials to give pinhole resistant coatings. Butyl stearate is a good low temperature plasticiser for paints. Butyl acetyl ricinoleate imparts good plate release and cold crack resistance to leather lacquers, and provides good handle and excellent low temperature flexibility to coated fabrics on thick unsupported sheetings.

Direct determination of corrosion inhibitor in aviation fuel by a column-switching technique using gel-permeation chromatography

Hitec E580 is added to aviation fuel as an antiwear agent and corrosion inhibitor. The normal concentration range is 10-20 ppm and the level may be determined by measuring the concentration of the major active ingredient, namely dimer acid (technical-grade dilinoleic acid). The method of Hillman et al. involves multiple extractions of the dimer acid from a large volume of fuel and measurement is achieved by gel-permeation chromatography (GPC) with refractive index detection. This paper describes an improved method. It uses an on-line precolumn, containing a polar packing, to extract the dimer acid from the fuel. Operation of a switching valve allows the precolumn to be flushed with tetrahydrofuran (THF), thus transferring the dimer acid to a GPC column. Refractive index detection is used. The two methods give results which are in acceptable agreement

The Effect of Phenolic Antioxidants on the Adsorption of the Antiwear Additive Dilinoleic Acid on Metals

The effects of phenolic antioxidants on the adsorption of the antiwear additive, dilinoleic acid, from dodecane onto metal surfaces have been measured. The adsorbents were the metals of the Lucas piston pump used in aviation fuel systems, viz cadmium, a tool steel and an aluminum bronze. For the latter two metals particularly, adsorption at 80°C and 100°C was enhanced by the presence of antioxidants. This is attributed to a reduction in the formation of solvent oxidation products which would otherwise compete for surface sites on the metals. Comparison of results at 150°C in air and under nitrogen support this interpretation. The role of the metal surface is discused both in terms of the nature of the adsorption sites and catalysis of reactions occurring in solution.

Kinetics of fatty acid adsorption from non-aqueous solutions onto metal surfaces. Part 2.—Dilinoleic acid

The kinetics of adsorption of the thermal dimer of linoleic acid from dodecane onto three metal surfaces have been examined. The rate of desorption of the surface species into pure dodecane has also been investigated. A general rate equation previously formulated to explain the behaviour of linoleic acid has been applied to the dimer acid adsorption kinetics.The existence of surface-coverage-dependent activation energies for adsorption and desorption has been postulated to explain the kinetic behaviour. Activation energies for adsorption were lower than for the monomer. The overall adsorption process is exothermic at zero coverage but adsorption entropies are positive as for the monomer. These results are discussed in relation to the overall adsorption process.

Lubricants. I. Preparation and properties of benzyl and substituted benzyl esters of dilinoleic acid

AbstractBenzyl and substituted benzyl esters of dilinoleic acid and of hydrogenated dilinoleic acid have been prepared in good yield. Some of the chemical characteristics and physical properties of the resulting products have been measured including a study of their thermal stability by thermogravimetry. Also, they have been examined by several of the bench tests used in laboratory evaluation of lubricants. Several of them compare favorably with control materials used in the study.