I have a bunch of raw pure tung oil and I'd like to attempt to polymerize some of it, but am not sure how hot to cook it, how long, etc.
I was going to experiment with small quantities, and thin with turpentine if it gets too thick, but want to ask around if anyone has processes they've found that work well.
First of all, don't let anyone discourage you from experimenting. Secondly, forget about it. You're highly likely to just ruin it all or, at best, do no good. It's a complicated process of heating AND cooling. It's about impossible to do reliably without pressurizing, controlling humidity levels and all sort of other controls. Getting it just right without ending up with a rubbery mess is more luck than anything else. You can't thin the too-polymerized oil at all. It doesn't work that way.
Good luck if you still decide to try it,
- Andrew
Hello Mark,
Wow, you've got a long road to "hoe" if you attempt to polymerise Tung oil yourself... This is a very complex and highly hazardous operation. It would be far easier and cheaper to just purchase Polymerised Tung oil from a supplier. Lee Valley has an excellent Polymerised Tung Oil that I use regularly that you may want to take a look at...
Both nonconjugated and conjugated drying oils like linseed and tung can be polymerised by heating under an inert atmosphere. These polymerised oils are then referred to as "Bodied Oils." To achieve the higher viscosities of bodied oils, nonconjugated oils are heated up to 320° Centigrade and conjugated oils are heated up to 240° Centigrade.
This increase in viscosity, or "body," is caused from thermal decomposition of naturally occurring hydroperoxides. This decomposition yields free radicals that contribute to a limited amount of cross-linking. This is a very complex procedure and cannot be achieved by do-it-yourselfers.
The heating of tung oil must be carefully monitored, or the polymerisation will lead to gelation of the oil. The viscosity can also be increased by passing air through the oil (known as Blown Oils) at high temperatures up to
150° Centigrade. Reactions similar to those observed in cross-linking cause oligomerization of the oil.You need lots of expensive equipment (a couple million dollars) and a team of chemists well versed in the procedure to give this a go. Heating oils is an EXTREME fire hazard and should not be attempted outside of a properly equipped laboratory with full protective measures and properly trained professional personnel in place.
What are you trying to achieve specifically with your raw Tung oil? Do you need a faster drying rate, higher gloss, better build etc? There is no doubt an easier way to accomplish what you need if you can give us a little more info. Please don't try heating the oil yourself. Take care and be safe!
Better Woodturning and Finishing Through Chemistry...
Steven D. Russell Eurowood Werks Woodturning Studio and Advanced Research Laboratory The Woodlands, Texas
Machinery, Tool and Product Testing for the Woodworking and Woodturning Industry
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