Polyurethane An Old Luan Shell? - Page 2

I thought Phenolic was from the beetle and Shellac was from tree sap...:confused:

Based on one of my companies sealers is a phenolic based sealer and we had a bad batch that smelled a bit like rotting corpses. Root cause was found to be the beetle batch it was made from.

I purchased shellac flakes in the past and dissolved them in alcohol. I could have sworn I read that this is derived from tree sap (and why the coaster was invented- spilled bourbon on antique furniture makes a mess!).

Dried phenolic is resistant to alcohol.

I could be wrong- it has happened before! (so I looked at the never-wrong authority, Wikipedia!)

Shellac is a resin secreted by the female lac bug, on trees in the forests of India and Thailand. It is processed and sold as dry flakes (pictured at right), which are dissolved in ethyl alcohol to make liquid shellac, which is used as a brush-on colorant, food glaze and wood finish. Shellac functions as a tough natural primer, sanding sealant, tannin-blocker, odour-blocker, stain, and high-gloss varnish. Shellac was once used in electrical applications as it possesses good insulation qualities and it seals out moisture. Phonograph (gramophone) records were also made of it during the pre-1950s, 78-rpm recording era.

From the time it replaced oil and wax finishes in the 19th century, shellac was one of the dominant wood finishes in the western world until it was largely replaced by nitrocellulose lacquer in the 1920s and 1930s.

Phenol formaldehyde resins (PF) are synthetic polymers obtained by the reaction of phenol or substituted phenol with formaldehyde. Phenolic resins are mainly used in the production of circuit boards. They are better known however for the production of molded products including pool balls, laboratory countertops, and as coatings and adhesives. In the form of Bakelite, they are the earliest commercial synthetic resin.

So, I learned something, but it does not explain why the bugs were found to be the cause of the smell in our Phenolic based sealer... Wierd!

The flakes make sense, as the secretions on the trees could easily be mistaken for sap (but I certainly was not the guy collecting it!)...