Polyester Resin and Wood Chips

[Ed_McDonnell]

Had some African Blackwood and Tulipwood chips that looked nice mixed together. Thought I could make a nice turning block by mixing them in with some polyester resin.

The resin will not cure. Not even after heating in an oven.

I've confirmed that the resin is good and that I didn't forget the catalyst.

I've never mixed oily woods into resin before. The resin took on a very dark dark brown coloring like it absorbed something from the wood. Is it possible that the oils in these (dalbergia) woods would prevent the resin from curing?

I know they play heck with polyurethane, but that's different chemistry as far as I know.

Any ideas?

Ed

 

[Ed Davidson]

Ed,

I think there may be something to your oily wood comment. I've tried casting PR into a cocobolo counterbore and it would not cure or bond to the wood...after a week, a gooey glob of resin would slide out of the wood's hole like a bad bowl movement

 

[Ed_McDonnell]

Ed - Thanks for the cocobolo report.

I just ran a little test. Prepared a batch of resin and divided it into 3 portions. Left one as a control. Added maple chips to one and blackwood chips to another.

The control and the maple chip sample cured as expected. The blackwood sample shows no sign of curing. Considering Ed's experience with cocobolo, I would suspect that all dalbergia species will inhibit curing.

I received an email from Alex McLaughlin that indicated that wood with a high or low PH will inhibit curing of the resin. Unfortunately I haven't been able to find any information online that give ph stats for wood.

Anyone know where I can find ph numbers for wood?

At this point I'm just going to avoid using polyester resin with dalbergia species. It would be nice if there was a way to predict other woods that would be problematic before finding out the hard way.

Any and all information / thougts welcome.

Ed

 

[Ed Davidson]

Ed,

Here's a list of woods that I have successfully bonded PR to: Redheart, Yellowheart, Osage Orange, Bloodwood, Mesquite, Chokte Viga, Bocote and Holly.

 

[Ed_McDonnell]

Thanks Ed. We can add maple to the list.

I've got about 30 different species in the shop right now. I may just bite the bullet and test the whole lot.

If I do I'll post the results.

Ed

 

[Brian Hahn]

Try epoxy instead

There's a very good chance that your problem was caused by the wood reacting with the catalyst and deactivating it.

Epoxy usually works better for bonding things and making composites than polyester resin. There are multiple reasons why epoxy works better: it is a glue to start with; it doesn't shrink when curing; and extractives from the wood don't significantly interfere with the curing process.

 

[Dave Smith]

Interesting information

I have had no problem with cocobolo and epoxy. I guess I never used polyester resin with cocobolo. Now I am wondering if you could leach the oils out of cocobolo with naphtha or lacquer thinner. Just an other thing to entertain the gray cells.

Dave Smith

Basking in sunshine in Mesa, AZ.