Tung Oil

Tung Oil Properties:
 

Item	Specification	Results
Apprence	Transparent or slightly turbid yellow liquid with inherent tung oil odor	Transparent or slightly turbid yellow liquid with inherent tung oil odor
Color (gardner)	8.0 max	7.5
Specific gravity (20°C)	0.935 – 0.940	0.9387
Refractive index (20°C)	1.516 – 1.555	1.5200
Iodine value(WIJS)	163 – 173	166,5
Saponification value	190 – 196	192,9
Moisture & Impurities	0.1% max	0.02
Free fatty acid	6.0% max	2,2
Worstall’s heat test	7.5 minutes max	7’ 05’’
Beta Tung oil test	No crystalline precipitate	Negative (no crystallization)

 
General Information:

Vernicia montana is a shrub or tree growing up to 15 meters tall.  The straight bole can be 25cm in diameter. The plant is evergreen in suitable climates, but can lose its leaves in areas with cold or dry seasons. The tree is often cultivated in tropical and subtropical areas for the valuable oil obtained from its seeds. The tree is sometimes planted as an ornamental and to provide shade.

Uses Notes:

The seeds contain 14 – 20% of a quick-drying oil, called  ‘abrasin oil’. This could easily mean that the seeds themselves contain 42 – 60% oil. Because of its similarity to ‘tung oil’ (from Vernicia fordii), the oils are often treated together as tung oil. The oil is used traditionally in the manufacture of paints and Chinese black ink; for waterproofing cloth and paper; caulking and painting ships; and as a lamp oil. It was also formerly used for insulating electric wires. Currently, its main use is in the production of paints and inks, while low-quality oil is processed into soap or linoleum. Teak oil which is sold for maintaining fine furniture is usually refined tung oil. 

Developments in environmental and health regulations have led to an increasing use of tung oil to line containers for food, beverages and medicines with an insulating coating. The main fatty acid of the oil is alpha-eleostearic acid . In eleostearic acid, the 3 double bonds are conjugated making them highly reactive. Under the influence of light or catalysts such as sulphur and iodine, alpha-eleostearic acid converts to beta-eleostearic acid, which is even more reactive and spontaneously polymerizes into a solid mass. The fatty acid composition of the oil is: α-eleostearic acid 75 – 80%, palmitic acid 4%, stearic acid about 1% and oleic acid 15%.

Traditionally, the fruits are collected when still green, placed in heaps and covered with straw or grass. The fruit pulp is allowed to rot until the seeds can be easily removed. The seeds are then crushed in a mill and roasted for a short time in shallow iron pans. The crushed mass is then thoroughly steamed and subsequently the fluid is pressed out of the cake yielding commercial wood oil. 

In modern processing, hulling of fruits is done by hand or mechanically. The seeds are then dried and shelled mechanically, after which the kernels are ground with some shell added to facilitate oil extraction. Cold-expression is done in screw presses yielding a clear, light-colored oil.

The cake may subsequently be warm-pressed or solvent-extracted to increase the yield, but the product is of lower quality.

The press cake, after extraction of the oil, is a good fertilizer, but it is poisonous and cannot be used as animal feed.

The wood is white, soft and perishable. It is only suitable for simple construction, core-stock for plywood, paper pulp.

The wood is used for fuel.