Wikipedia has a decent discussion under the "linseed oil" heading, including:
Having a high content of di- and triunsaturated esters, linseed oil is particularly susceptible to polymerization reactions upon exposure to oxygen in air. This polymerization, which is called "drying," results in the rigidification of the material. The drying process can be so exothermic as to pose a fire hazard under certain circumstances. Rags soaked with linseed oil stored in a pile are considered a fire hazard because they provide a large surface area for oxidation of the oil, and the oil oxidizes quickly. The oxidation of linseed oil is an exothermic reaction, which accelerates as the temperature of the rags increases. When heat accumulation exceeds the rate of heat dissipation into the environment, the temperature increases and may eventually become hot enough to make the rags spontaneously combust. The "drying oil" entry goes into more detail: A drying oil is an oil that hardens to a tough, solid film after a period of exposure to air. The oil does not harden through the evaporation of water or other solvents, but through a chemical reaction in which the components crosslink by the action of oxygen. Drying oils are a key component of oil paint and some varnishes. Some commonly used drying oils include linseed (flax seed) oil, tung oil, poppy seed oil, perilla oil, and walnut oil. and there are lots more details here, including the note that drying oils initially increase in weight significantly (17% for linseed) as they dry, due to absorption of oxygen.. It also reminds us that because of polymerization linseed oil is used as a binder/ardener for things like linoleum, wood finishes, putty, etc. so we may want to further consider any "drying" oils for densified fuel applications. "Boiled linseed oil" is the name given to a product that is particularly good for hard coatings - the heat treatment starts the polymerization. Charlie ________________________________ From: "[email protected]" <[email protected]> To: [email protected]; Discussion of biomass cooking stoves <[email protected]> Sent: Tue, January 25, 2011 12:03:57 AM Subject: Re: [Stoves] (no subject) [Jatropha cake properties] On Monday 24 January 2011 23:44:30 Peter verhaart wrote: > If Jatropha oil is a non drying oil (like castor oil), you are in deep > oil. If Jatropha oil is a drying oil, you might try using a drying > accelerator for paint and/or place the briquettes in an oven. Hi Peter I don't know whether Jatropha is a drying oil. I believe linseed is and cotton rags allowed to dry with linseed on then heat up and can self ignite, Does anyone know the mechanism for this? AJH _______________________________________________ Stoves mailing list to Send a Message to the list, use the email address Stoves mailing list to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org for more Biomass Cooking Stoves, News and Information see our web site: http://www.bioenergylists.org/ [email protected] http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org
_______________________________________________ Stoves mailing list to Send a Message to the list, use the email address Stoves mailing list to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org for more Biomass Cooking Stoves, News and Information see our web site: http://www.bioenergylists.org/ [email protected] http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org
