plywood manufactured with epoxy? - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: May 02, 2019, 05:56:23 am
content: So plywood uses some kind of weird glues that are often toxic. (formaldehyde)Despite the unslightly appearance, is there a grade of plywood manufactured with high end engineering epoxies?I don't mean coating it. I mean in the plywood factory, what would change if you made the plywood with the best epoxy you can get your hands on? Can the wood be made stronger? Maybe throw a few carbon fiber layers in there too?

author: helius
author_rank: Super Contributor
timestamp: May 02, 2019, 06:21:26 am
content: The adhesive needs to be a thermoset resin that resists water and creepage. The way plywood is made, the glue is sprayed onto the plies and remains workable for a long time. It is cured by the heated press that bends or stamps the wood at the same time. Most adhesives do not work like this: they either cure too quickly at room temperature or don't cure quickly enough at high temperature.

author: ealex
author_rank: Frequent Contributor
timestamp: May 02, 2019, 06:35:00 am
content: I tried soaking some "laser plywood" with thin epoxy resin.The result was quite stiff but also very heavy, as it will soak a lot of resin - I don't think there are many uses for it.You can find plywood that uses less toxic glues (the one marketed for laser cutting for example)You can make some quick experiments - get some thin wood veneer and thin epoxy, some glass sheets and silicone cooking mats (and gloves). Cut some veneer pieces and some other things you want to laminate, apply resin, layer them, clamp them between the glass sheets with decent pressure (maybe you can get some thick wood pieces, or metal) and let them harden for 48h (depending on the resin).I used the silicone cooking mats to keep the resin away from the working surface, the resin won't stick to them once it's hardened.You can use them between the clamps as well.I got the materials for a RC hobby store in my area, you might have to find other sources.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 02, 2019, 07:08:59 am
content: The formaldehyde "based" glue is the cheapest one and if not used in large quantity in poorly ventilated rooms is no a real problem. It is also released from natural wood. Epoxy glue is rather expensive and thus not likely used for plywood. Chances are good to find polyurthan based glues in some more water resistant grades. At least OSB panels are often using this type of glue.

author: Ian.M
author_rank: Super Contributor
timestamp: May 02, 2019, 07:52:39 am
content: Epoxy is relatively high cost, so using wood for the oriented fibres that provide most of the strength of the composite isn't cost-effective. Also as mentioned above it isn't very compatible with the plywood production process. However a low density balsa wood core is quite often used in epoxy composites between skins reinforced with glass, carbon or aramid fibres.If you want to experiment with sheet form epoxy composites, consider vacuum bagging to provide the clamping pressure (up to approx 15 PSI) while the laminate is curing. For vacuum bagging, it doesn't have to be a 'bag' as such, one can just tape down the edges of plastic sheeting over the laminate stack onto a non-porous substrate using duct tape + caulk to seal it at any creases. The bag or plastic sheeting needs a vacuum port - get one from a fibreglass materials supplier, or make one from a sink waste, with the main drain end blanked off and the vacuum line connected to the overflow T arm. If your bag isn't totally leak-free you'll need to keep the pump running after the initial pull-down so its a good idea to have a much smaller pump rated for continuous running on the same manifold to keep up with any leaks so you can shut the main pump off. If you need less clamping pressure e.g. to prevent foam core materials collapsing, you'll need a vacuum regulator or a vacuum reservoir and adjustable vacuum switch to control the pump.

author: German_EE
author_rank: Super Contributor
timestamp: May 04, 2019, 04:26:52 pm
content: Take a look at the marine plywoods used to construct boats, some of them may use epoxy.

author: bdunham7
author_rank: Super Contributor
timestamp: May 05, 2019, 02:48:47 am
content: I'm not aware of epoxy plywoods, but there is a marine product that is used for construction and restoration that is a set of epoxies of various viscosities that soak into the wood and make it very strong. I had a friend who restored a somewhat rotted Chris Craft this way and the end result was pretty stiff and strong. I imagine you could make a pretty tough structural component using OSB and soaking it in the thin variety of epoxy. What are you trying to do?

author: coppercone2
author_rank: Super Contributor
timestamp: May 05, 2019, 04:01:12 am
content: I am not trying to do anything, I just had a random thought when I looked at delapitated wood I was throwing away while cleaning outside

author: German_EE
author_rank: Super Contributor
timestamp: May 05, 2019, 08:48:18 am
content: Here's another random thought. Next time we want to build something reasonably large we make the chassis from plywood then soak it in epoxy for strength. Probably no good for RF but it might make an interesting audio project and shorts to chassis would never be an issue.Years ago I heard of someone who made his front panels from cardboard then soaked them in model airplane dope. He reckoned that they were as strong as plastic but much easier to work with.

author: coppercone2
author_rank: Super Contributor
timestamp: May 05, 2019, 04:06:06 pm
content: I like that idea for a chassis exterior, I do like my metal chassis for electrical reasons but I like another layer for safety, handling, corrosion, touch, etc reasons.I think we typically end at metal because its cheap.I am thinking just make a chassis and glue the epoxy soaked wood panels to the outside of the chassis then finish it like a speed boat.Do you just let it soak in? Do you need a vacuum or thinner? Will it still worked on stained wood, if you want a nicer look? Or can you add stain to the epoxy, or some kind of dye, for wood ?Can you recommend a product? I have a chassis project that I think I will try this on. I am thinking put 1/4 inch? (good for soaking?) plywood panels on 12 gauge sheet steel box.I guess fire load is reduced too though. An epoxy wood covered box is gonna burn real good, right? Any thoughts on this?

author: German_EE
author_rank: Super Contributor
timestamp: May 05, 2019, 04:23:36 pm
content: So many questions, and my experience of bulk epoxy consists of one canoe twenty years agoSome epoxies are the same consistency as paint after mixing, they have to be so that they can soak into the glass fiber matting used for boat construction, and you DON'T want any voids here or the surface finish will be ruined. I suspect that this idea won't work on stained wood because the stain will soak into the pores, you can however add colors to the epoxy during mixing, this is how the boats end up different colors.Using any sort of thinner around epoxy will destroy the bond so forget about that idea. You even need to wait for IPA to evaporate after degreasing or things will go bad pretty quickly.So, the best thing I can suggest is that you go to your local boat builder and see what they have and how they use it. I am quite sure that in the time since I used bulk epoxies the technology will have changed.

author: coppercone2
author_rank: Super Contributor
timestamp: May 05, 2019, 04:30:23 pm
content: how about the whole suitability for electrical equipment chassis even with a metal liner because of fire reasons?Is it wise? what maximum thickness do you think is reasonable before it turns into a gross fire hazard? Maybe better to leave a air gap between the metal and wood to act as a insulator then to paste the wood onto the metal directly, even if it is mechanically stronger.

author: Bud
author_rank: Super Contributor
timestamp: May 06, 2019, 12:09:57 pm
content: How are you going to cut such epoxy plywood, it may be a nightmare.

author: Ian.M
author_rank: Super Contributor
timestamp: May 06, 2019, 01:13:33 pm
content: Epoxy cuts quite easily with the usual powertools if it isn't reinforced with glass, carbon or aramid fibres or mixed with silica, glass beads or other hard fillers. It would probably be less of a nightmare than cutting ordinary ply as splintering on face cross-grain cuts would be much reduced.However, I think this is another one of Coppercone's dumb ideas. Epoxy as a coating has notably poor UV resistance, and a few years of sunlight will degrade the surface to a chalky appearance. Good quality WBP ply with a hardwood face veneer doesn't need epoxying to make it durable if not directly exposed to weathering or permanently damp. Also, glueing plywood sheets onto a steel chassis is guaranteed to cause trouble - the epoxy hardener rapidly rusts steel, and the different coefficients of thermal expansion and wood expansion/contraction with varying humidity are likely to cause the panels to warp.IMHO assemble the ply cabinet with epoxy and battens inside the corners, protecting the exterior face of each panel with masking tape up to its edge to avoid surface epoxy contamination, then stain and finish with lacquer or a polyurethane varnish. The steel chassis should be an inverted tray section, screwed to battens epoxied to the cabinet interior. Many period valve radios and radiograms were built this way, usually with glues that are vastly inferior to modern epoxies, and their cabinets have proved to be durable.If fire resistance is an issue (and it shouldn't be or most plastics would also be found unsuitable), there are additives (usually borax based) which can make epoxy self-extinguishing, and fire retardant coatings that can be applied to the plywood.