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  #1  
Old 05-16-2003, 03:15 PM
David Peterson David Peterson is offline
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stabilizing wood

For those of you interested in stabilizing your own wood, I came across a very interesting article on the web about different polymers being used. It's mainly focused on musical instruments, but has a great section on MMA impregnation in wood.

Here's the link.

I have found that Aldrich Chemical will supply any of the needed chemicals, including benzoil peroxide (catalyst), Dibutyl Phthalate (catalyst stabilizer), Methyl Methacrylate, and Butyl Methacrylate. I called about the MMA and it's $40 for 2 liters. Not bad pricing, and I believe it's not considered hazardous as far as the HAZMAT fee goes. I found a good recipe that allows you to adjust the block hardness according to how much butyl methacrylate to methyl methacrylate you add. A 3:1 or 4:1 ratio is suggested. Mix the Benzoil Peroxide and the Dibutyl Phthalate (1:1 w:v) and stir it into the Methacrylate mix to start the polymerization. There's lots of information out there about this reaction from chemistry sites where they need to use the embedding kits for organ slices. I'll keep writing my findings if anyone is interested.

-Dave

I'm going to add the section about MMA so the search function on CKD will pick it up. Here goes:


ALTERNATIVE IMPREGNATION STRATEGIES

Just when plastic recorders are making their products look like wood, there is interest in making wood/plastic composites. Sometimes the goal is cost, sometimes fashion, and sometimes it is the elusive immortal woodwind. The technique is not new. Amish farmers have impregnated maple wheel bearings for over a century with lard. The WWII Maytag ringer-washers used mineral wax impregnated maple. Most techniques today are aimed at the floor panel, knife handle, and designer pen body market. But woodwind makers may possibly realize shape stabilization, and water repellency. Only time will tell.

METHYL METHACRYLATE (MMA): Wood Stabilizing Specialists Inc. (Cedar Falls, IA), has produced a billet of cherry impregnated with polymerized methyl methacrylate. Scott Hirsch, a flute maker in Coleville, WA, has made instruments from the material. Wildwoods (Monclova, OH) has produced similar impregnated billets of maple and black-dyed birch for Powell Flutes (Waltham, MA). Tim Bernett of Powell Flute made an impregnated maple alto in the mid '80s. Bamboo has been treated for use in making Japanese flutes; Yamaha has worked with impregnated rosewood for clarinets. Roger Rowell of the USDA Forest Product Laboratory has explored impregnating maple wood with MMA for recorder manufacture.

The pure polymer is the well known Lucite or Plexiglass. Such impregnated woods do pose challenges to the craftsman because of brittleness, the need to use low turning speeds and coolant because of the low melting point of the plastic, and a tendency to clog sanding materials. Finished instruments play well and seem to have good dimensional stability. Some results are reported in Woodwind Quarterly, #2, August 1993. Such impregnations for many commercial purposes began in the 1960's. Ken Caines of WSSI reports load factors of about 50% are normal with common woods. Exotics, such as ebony, accept much less polymer (<10%) and are prone to bleed displaced "wood oils" for many months after treatment. This can be removed by wiping with acetone. Odors from the monomer are often prominent, and are due to excessive water in the impregnated wood (>10%), or improper curing. Drying (40 C) can remove such odors.

OTHER ACRYLATES: Many other efforts in wood impregnation exist. Daniel Deitch, a Baroque woodwind maker in San Francisco, has utilized cyanoacrylate impregnation for wood stabilization. MMA has the structure H2C=C(CH3)COOCH3, while a typical cyanoacrylate has a structure H2C=C(CN)COOCH3. They differ by the substitution of a -CN group for a -CH3. This substitution makes it easier for the material to polymerize into long carbon chains, much like a zipper closes. The cyanoacrylates are used as rapid setting "glues". Deitch swabs out the finished bores with the cyanoacrylates, lets the material polymerize, and then finishes the interior surface. Deitch also reports that he has been pleased with a technique for finishing the exterior learned from Rod Cameron, a flutemaker from Mendocino, CA. A few drops of the cyanoacrylate are added to linseed oil, and the mixture applied as a hardening finish to the exterior. The cyanoacrylate accelerates the hardening of the mixture. Do not be concerned about the presence of the -CN group in the molecule. It is an organic nitrile or cyanide, not an inorganic cyanide. The latter are toxic, but the organic -CN is not. Some artisans find the cyanoacrylic bore finish beads water excessively.

OTHER FORMS OF POLYMERIZATION: The polymerization of both the cyanoacrylates and methacrylates depend upon chemical induced free radical formation to begin the polymerization. A free radical is a carbon with only three groups around it, and one lone electron. This poses some interesting problems in getting complete penetration into all the void space of the porous wood. The cyanoacrylates react with air and polymerize quite rapidly, providing good near surface penetration. Free radical initiators added to the methacrylates allow somewhat deeper penetration before blockage occurs. Firms such as Applied Radiant Energy (Lynchburg, VA) have developed an alternate strategy for achieving an even more complete penetration. The methyl methacrylate is forced into the wood by first applying a vacuum, then flooding the chamber with the liquid acrylate, and finally bringing the head space up to atmospheric pressure. They can achieve loadings of 10-100% in this way, filling a great deal of the void space. The polymerization of the material is then induced by exposure to gamma radiation. This ionizing radiation penetrates the wood completely and evenly, allowing uniform polymer hardening throughout. The degree of polymerization can be carefully controlled by the amount of irradiation. This permits careful adjustment of the working properties of the resulting composite. Don't be concerned about the radiation initiator. Gamma radiation is just like an X-Ray beam. Once the beam is turned off, its gone. The route has been used to sterilize food for long term preservation. Gamma radiation DOES NOT consist of radioactive particles which have long half-lives, and which slowly emit hazardous particles and radiation.

Billets up to 8"x8" have been treated. Ash, oak, pine and poplar are common. More exotic woods include cherry, ebony, and jatoba (Brazilian cherry). Best results come from using the heart wood. Robert Turner, a Charlottesville, VA recorder maker, is experimenting with some of the materials.

PHYSICAL AND PSYCHEDELIC PROPERTIES: It should be noted that these treatments do not prevent the penetration of water vapor into the wood. It is merely slowed down, as described earlier. The composites have increased tensile strength and lower impact resistance due to their brittleness. They are harder. Little objective acoustic data on composite woodwinds are available, although strong opinions exist.

Most composite manufacturers are focusing on dyed impregnated woods, often with multicolored, swirling patterns for designer products. Imagine a recorder playing cool jazz or hot Blues with a color scheme to match! Avant-garde players could have complete sets. On the other hand, although the Pacific Rim produces the greater part of ABS plastic instruments, most players there seem to prefer buying perfect, natural material woodwinds. But good grenadilla and rosewood are becoming scarce. Interesting marketing problems.

Wood, composite or plastic? Some subjective panels claim they can tell the difference; others claim no distinction. A paradox.
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  #2  
Old 05-21-2003, 09:45 PM
David Peterson David Peterson is offline
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For those of you interested in research on stabilizing wood, I've compiled a bunch of articles that I thought might prove useful. After looking over my old links and finding half of them broken, I made them all into PDFs. I think it will be a good library of information. Take a look and let me know what you think.
Click Here to go to the Library

-Dave
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Old 05-21-2003, 10:31 PM
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tmickley tmickley is offline
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Just read many of the pdf files you posted in your library. MMA looks like the stuff to use. What method are you using to saturate your wood and then to cure it?
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Old 05-27-2003, 10:17 AM
David Peterson David Peterson is offline
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tmickley,
This information I have is just the research so far. I haven't ordered any MMA yet, but will next week from Aldrich. I've played with styrene resin and it's very similar. The way to get it into the wood is just the vacuum chamber method. I draw a vacuum, let it out, draw vacuum, release, etc.. That seems to get full penetration without using pressure AND a vacuum.

MMA, like styrene, is kicked off by a catalyst. It needs to start the free radical polymerization of the monomer (MMA) that actually makes the block solid. You can use benzoil peroxide to cure it, or introduce a UV sensitizing agent and put it under UV light to cure it. I would go the peroxide route because I don't see how UV can penetrate the dense wood knife makers use. I don't know much about UV curing though. My first trial is going to be butyl methacrylate and MMA combined because you can adjust the hardness of the block by the proportion of BMA and MMA.

I've talked with Rohm and Haas, the company that makes alot of the consolidants for conservation, and those chemicals are mostly copolymers. These are not going to work like the monomers of MMA. Acryloid B-72 is a copolymer of PMMA and just seems to coat the surfaces inside the wood, not fill the voids. B-72 is cut with acetone and then a vacuum is pulled to get it into the wood. After letting it dry for a week, I found that the PMMA is just deposited on the surface of the wood grain as the acetone evaporates. This is not what I'm after. To test this, I took some B-72 dissolved in acetone and added the peroxide catalyst. It "pulled" the copolymer out of solution and hardened it into a ball in the middle of the acetone. I know you didn't ask about the B-72, but it illustrates the difference between PMMA copolymers and actual MMA monomer. When you add the catalyst to MMA monomer, it make one solid block of PMMA. I think the MMA monomer is the way to go. I hope I didn't bore you with this.

-Dave
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Old 05-27-2003, 12:25 PM
fitzo fitzo is offline
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Dave,

What have you found out about the presence of inhibitors in the monomer? A friend bought a big bucket of MMA and then found out it is inhibited, and he literally had to chromatograph the stuff over silica to remove the inhibitor. What I have read says the polymerization will self-initiate if the inhibitor is gone, but certainly the use of a catalyst will speed up the process. I am getting old, and what I read several months ago is not as firm as stuff I learned 30 years ago.

Dang, this is terrible... I thought I was done with chemistry when I retired, but threads like this perk up my ears, still... hehe. I guess "you can take the boy outta the lab, but..."
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Old 05-27-2003, 05:56 PM
whv whv is offline
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thanx much for sharing your research, dave, and for taking the time to archive those .pdf files.


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Old 05-28-2003, 12:25 AM
David Peterson David Peterson is offline
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I'm glad to see some people are interested in this chemistry stuff. I get such a kick out of it, although I'm far from being an expert. I just like the learning process.

Everything I have read says the inhibitor does not interfere with the catalyst and the reaction. It's true that it keeps the MMA from polymerizing by itself due to heat or UV, but they say it doesn't cause any problems with the catalyzed reaction. Some chemists would probably insist on the pure form, but for stabilizing wood I don't see it as a problem (yet). I have read a few articles about pre-polymerizing the MMA and then keeping it in the fridge for up to a year without problems. I'll post more about that later when I have some MMA to test with.

-Dave
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Old 05-29-2003, 03:39 PM
whv whv is offline
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i would suspect, dave, that they have figured out how to use an inhibitor that will be excluded from the polymer once the catalyst kicks off the reaction. have fun with the research.


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Last edited by whv; 06-03-2003 at 04:49 PM.
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Old 05-29-2003, 04:16 PM
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Don Halter Don Halter is offline
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Any idea where I can find more specific information on the irradiation techniques (such as activity/dose-rate needed for polymerization) or UV light curing?

Thanks,
Don


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Old 05-30-2003, 03:07 PM
David Peterson David Peterson is offline
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I have read that the inhibitor only has an effect when there is no catalyst present. It is a fairly weak inhibitor and only stops stray UV or heat from polymerizing the MMA in the bottle. Once catalyst is added, it overpowers the inhibitor and initiates the polymerization reaction.

Don,
Some of the info I have in my library contains info about UV curing and a little on radiation. I have come across some info in my search, but I didn't keep it because I was only looking at peroxide catalysts. If you have access to a radiation source, they say that's the best way to do it.

-Dave
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Old 06-03-2003, 04:45 PM
David Peterson David Peterson is offline
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Does anyone know a place in Colorado that might have MMA? I've had the hardest time trying to purchase MMA through Aldrich and Spectrum. They say that UPS will not deliver hazardous materials to a residence and the chemical companies will only ship to hospitals and chemistry labs. How the heck do I get ahold of MMA? :confused: Any ideas on a way around this?
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Old 06-04-2003, 04:56 PM
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Don Halter Don Halter is offline
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As a radiation safety officer, I have quite few sources and types of radiation at my disposal as well as a food irradiator with some massive x-ray and electron fields that I can probably get some sort of "deal" worked out on (I'm already making a pair of knives for the director of the facility and his son). I just didn't know how much radiation was needed.


Updated:
Found this:
http://accelconf.web.cern.ch/AccelCo...ERS/WEP126.PDF

That's a LOT of radiation! The new facility we just built here would do it in one tenth of the time...but scheduling beam time would probably cost more than a few favours!


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Last edited by Don Halter; 06-04-2003 at 05:05 PM.
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Old 06-05-2003, 11:48 AM
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Jeremy Krammes Jeremy Krammes is offline
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I see a lot of talk of MMA, I think this the same stuff used in acrylic nails as a hardning agent (my wife owns a salon). If it is the same stuff, it is illegal in some states including mine, PA. Illegal for use in fingernail application. My wife told me some people develope an algery to it over time, and loose there fingers because of the algery. I'm NOT SURE if this is the same stuff, but I thought I would throw this out there just in case.

Jeremy...
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Old 06-05-2003, 10:05 PM
David Peterson David Peterson is offline
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Jeremy,
Yes, MMA is the same stuff they use for fake nails. It's also used a lot in dentistry, plexiglas, glues, lexan, eyeglasses, bulletproof windows, jet fighter windows, eyeball lenses, casting resins, and too many other products to mention. The monomer is hazardous because it absorbs through the skin, and is explosive. The catalyst is worse than the monomer though. Any peroxides are very explosive when dry, and methyl ethyl ketone peroxide can instantly blind you. This is the same stuff they use for fiberglass kits in the automotive section of any hardware store.

The polymer of MMA (PMMA) is completely inert, and has been found embedded in the bodies of fighter pilots (their windows exploded) after 30 years with no harmful efftects. MMA is not illegal per se, but it's illegal for use in salons. The problem I have getting it is UPS charges a hazmat fee, won't deliver to a residence, and then the chemical companies say you have to have facilities to dispose of harzardous waste before they ship to you. That's called CYA....Cover Your Ass. I have found it in Denver, but it's three times the price. They are charging so much because they know you can't order it.

I'm looking into other monomers that aren't so much of a pain. Styrene monomer is one option you can buy in any hardware or automotive store. It's a combination of polyester and styrene monomer for fiberglass. There are also urethane resins for casting, polyesters and then the acrylics. What I'm after is something that doesn't use solvents that evaporate and cause it to just coat the surface of the wood fibers. I want something to solidify completely by polymerization. CPES, Acryloid B-72, Rotted Wood Hardener, brick sealer, acrylic paint, etc all just leave a coating and don't fill voids. I'm not saying they are wrong to use, just not what I'm looking for. I've found some clear casting resin at Hobby Lobby and something they use for making simulated water for hobby trains. I haven't got all of my results yet, but will post them when I do. I know this is long winded, but it's an area of study that I really enjoy. I like the challenge.

-Dave
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Old 06-28-2003, 12:07 PM
etp777 etp777 is offline
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Do you happen to know of any way to thin the Styrene monomers' for appliation? As is, from either the hardware store or auto parts store, it tends to be a bit thick, at least in my experience, if there was a way to thin it for easier use, I think it would be more useful, and give better products(have used it to make some micarta, or my version anyways, and it gave a good product, but the fibers of fabric aren't completely saturated, as it's still a bit thick. If I could make it thinner, would work better(as of now, stuff fuzzes a little on grdnding, so after grinding, go back and do a super glue finish).
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