Polymerization of Drying Oils

Wexler, Herman

doi:10.1021/cr60232a001

Cited by 156 publications

(79 citation statements)

References 99 publications

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“…oxidative polymerization. Such polymeric species rarely become larger than trimers or tetramers 12,23,42 , although an explicitly stated reason for this cannot be found in the open literature. One of the obvious results of polymer formation is an increase in the oil viscosity 18,43 .…”

Section: Secondary Products Of Oxidationmentioning

confidence: 99%

“…One of the obvious results of polymer formation is an increase in the oil viscosity 18,43 . Under conditions where oxygen is available, fatty acid moieties are joined by both C-O-C linkages 3,23,42 and C-C linkages 42 . When ROOH decomposition occurs under an inert atmosphere, C-C linkages in resulting polymers are observed 23 .…”

Section: Secondary Products Of Oxidationmentioning

confidence: 99%

“…Under conditions where oxygen is available, fatty acid moieties are joined by both C-O-C linkages 3,23,42 and C-C linkages 42 . When ROOH decomposition occurs under an inert atmosphere, C-C linkages in resulting polymers are observed 23 . The fact that oxygen is incorporated in the oxidative polymerization has been demonstrated by the oxidation of soybean oil and the isolation and analysis of the resulting polymeric compounds.…”

Section: Secondary Products Of Oxidationmentioning

confidence: 99%

“…Once this isomerization has begun, a conjugated diene group from one fatty acid chain can react with a single olefin group from another fatty acid chain to form a cyclohexene ring 2,42 . This reaction between a conjugated di-olefin and a mono-olefin group is called the Diels Alder reaction, and it becomes important at temperatures of 250-300°C or more 8,18,23 . The products formed are called dimers.…”

Section: Thermal Polymerizationmentioning

confidence: 99%

“…Thermal polymerization can also form trimers, but there is disagreement as to how they form. One study concluded that trimers are formed by reaction of an isolated double bond in a dimer side chain with a conjugated diene from another fatty oil or ester molecule (a Diels Alder reaction) 23 . However, an earlier study provided evidence that may support the non-Diels Alder coupling of two side chain olefin groups from a dimer and a fatty oil molecule 8 .…”

Section: Thermal Polymerizationmentioning

confidence: 99%

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Characterization of Biodiesel Oxidation and Oxidation Products

2005

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This report must be reproduced in full,unless SwRI approves a summary or abridgement. iii EXECUTIVE SUMMARY Stability Chemistry FundamentalsChemical reactivity of fatty oils and esters can be divided into oxidative and thermal instability. Both of these types of instability are determined by the amount and configuration of the olefinic unsaturation on the fatty acid chains. Many of the plant-derived fatty oils, including soy and rapeseed, contain polyunsaturated fatty acid chains that are methylene-interrupted rather than conjugated. This structural fact is key to understanding both oxidative and thermal instability.In oxidative instability, the methylene carbons between the olefinic carbons are the sites of first attack. After hydrogen is removed from such carbons oxygen rapidly attacks and a hydroperoxide is ultimately formed where the polyunsaturation has been isomerized to include a conjugated diene. This reaction is a chain mechanism that can proceed rapidly once an initial induction period has occurred. The greater the level of unsaturation in a fatty oil or ester, the more susceptible it will be to oxidation. Once the hydroperoxides have formed, they decompose and inter-react to form numerous secondary oxidation products including aldehydes, alcohols, shorter chain carboxylic acids, and higher molecular weight oligomers often called polymers. Another polymerization mechanism, vinyl polymerization, has been proposed as being part of the degradation process of fatty oils and esters. However, conventional understanding of oxidation chemistry would imply that such processes would not be significant when oxygen was abundant, so its precise level of importance has not been determined.Metals, free fatty acids, acidic fuel additives, the size of the alcohol group (for mono-esters), and the presence of natural antioxidants can all impact the oxidative stability of fatty oils and/or esters. Oxidation can also be catalyzed by light, but such photo-oxidation should not be a significant factor for the manufacture and transportation of biodiesel fuel.Thermal polymerization of fatty oils and esters does not become important until temperatures of 250-300°C are reached. This is because the methylene-interrupted polyunsaturated structure cannot participate in such reactions until it isomerizes into a conjugated configuration, and such isomerization will not occur until that temperature range is reached. Thermal polymerization occurs by the Diels Alder reaction, and two fatty acid chains are linked by a cyclohexene ring. Higher order oligomers are also possible, although the exact mechanism is still not established. Certain thermal polymerization products in used cooking oils may carry over to non-distilled biodiesel. The verification of such compounds and their impact on fuel quality has not been determined. Thermal polymerization may be of limited importance in biodiesel fuel that is repeatedly heated by the engine and recycled to the fuel tank before actual combustion. However, thermal polymerization will not impact stor...

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Section: Secondary Products Of Oxidationmentioning

confidence: 99%

Section: Secondary Products Of Oxidationmentioning

confidence: 99%

Section: Secondary Products Of Oxidationmentioning

confidence: 99%

Section: Thermal Polymerizationmentioning

confidence: 99%

Section: Thermal Polymerizationmentioning

confidence: 99%

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Characterization of Biodiesel Oxidation and Oxidation Products

2005

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Drying Oils

Wicks¹

2000

Kirk-Othmer Encyclopedia of Chemical Technology

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Natural and synthetic drying oils are discussed. Occurrence, isolation, composition, and analysis of oils is covered. Mechanism of drying through free‐radical initiated autoxidation is described with particular emphasis, in the case of oils with nonconjugated double bonds, of the role of activated methylene groups between double bonds. The reactions are catalyzed by oil‐soluble transition‐metal salts. Modified and synthetic oils include: varnishes, synthetically conjugated oils, esters of higher functionality polyols, maleic anhydride‐modified oils, and vinyl‐modified oils. Data on economic aspects and lists of specifications are included. Natural drying and semidrying oils as well as their fatty acids are used in making alkyds, epoxy esters, and urethane oils, which can properly be considered synthetic drying oils. Uses of drying oils discussed include paints, printing inks, and other uses.

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Carboxylic Acids, Survey

Bagby¹

2000

Kirk-Othmer Encyclopedia of Chemical Technology

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Polymerization of Drying Oils

Cited by 156 publications

References 99 publications

Characterization of Biodiesel Oxidation and Oxidation Products

Characterization of Biodiesel Oxidation and Oxidation Products

Drying Oils

Carboxylic Acids, Survey

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