Low temperature oxidation of linseed oil: a review

Abstract

This review analyses and summarises the previous investigations on the oxidation of linseed oil and the self-heating of cotton and other materials impregnated with the oil. It discusses the composition and chemical structure of linseed oil, including its drying properties. The review describes several experimental methods used to test the propensity of the oil to induce spontaneous heating and ignition of lignocellulosic materials soaked with the oil. It covers the thermal ignition of the lignocellulosic substrates impregnated with the oil and it critically evaluates the analytical methods applied to investigate the oxidation reactions of linseed oil. Initiation of radical chains by singlet oxygen ( 1 Δ g ), and their propagation underpin the mechanism of oxidation of linseed oil, leading to the self-heating and formation of volatile organic species and higher molecular weight compounds. The review also discusses the role of metal complexes of cobalt, iron and manganese in catalysing the oxidative drying of linseed oil, summarising some kinetic parameters such as the rate constants of the peroxidation reactions. With respect to fire safety, the classical theory of self-ignition does not account for radical and catalytic reactions and appears to offer limited insights into the autoignition of lignocellulosic materials soaked with linseed oil. New theoretical and numerical treatments of oxidation of such materials need to be developed. The self-ignition induced by linseed oil is predicated on the presence of both a metal catalyst and a lignocellulosic substrate, and the absence of any prior thermal treatment of the oil, which destroys both peroxy radicals and singlet O 2 sensitisers. An overview of peroxyl chemistry included in the article will be useful to those working in areas of fire science, paint drying, indoor air quality, biofuels and lipid oxidation.

Linseed Oil and its Tendency to Self-Heat

“…There is an induction period of about 50 min clearly seen for experiment on the cotton wool substrate before a fast increase of carbon dioxide. This agrees with the experimental measurements reported by Lazzari and Chiantore who observed a fast increase in the abundance of hydroxyl groups after an induction time of about 4 h [13]. In this case, cotton wool exhibits an inhibiting effect on the oxidation, possibly as a result of antioxidant present in the cotton wool.…”

“…Subsequently, this radical abstracts an allylic hydrogen from another parent molecule to form a hydroperoxide which then decomposes into alkoxy and hydroxyl radicals. This chain of events supports the propagation of the autoxidation reaction [13]. Metal catalysts can reduce the activation energy required for the decomposition of hydroperoxide from 45-85 to 20-25 kJ mol -1 [14].…”

A Chemical Mechanism for Self-ignition in a Peat Stack

“…Fortunately the bucket was in the driveway and away from the house -a good precaution! According to Juita et al [18] initiation of radical chains by singlet oxygen ( 1 Δ g ), and their propagation underpin the mechanism of oxidation of linseed oil, leading to the self-heating and formation of volatile organic species and higher molecular weight compounds.…”

“…Alkoxyl radicals can cross link with each other to form polymerization product and also can undergo scission reaction to form products such as aldehydes, acids and lower hydrocarbons. [18] the decomposition products of peroxide compounds include alkoxyl, peroxyl and hydroxyl radicals. The OH radical is the primary species responsible for the consumption of organic compounds under atmospheric conditions.…”

Production of Biodiesel from a mixture of Karanja and Linseed oils: Optimization of process parameters

“…Linseed oil contains 60% linolenic acid, which is the most unsaturated acids. This linolenic acid affects the drying property of oil to make it suitable for drying in alkyd paints [17]. The comparison of fatty acid composition of linseed oil and karanja oil are given in Table 1 [18].…”