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User avatar
By bowgarguide
#1336053
I ask this before in a post and never got a comment, does mixing wood flour cabisil or any other filler
increase the holding properties of epoxy.
I notice several folks have listed mixing it to use as glue.
Ron
User avatar
By bowgarguide
#1336187
Aerosil-Cabosil
(Fumed Silica) ( Aer-o-sil 200 )
Thickening agent for epoxies, polyesters, and urethanes. Thicken resins to your own taste by adding varying amounts. Ideal for making adhesives and putties for gluing wood, fiberglass, stone, concrete, etc. However, adding this product will make the cured resin much more difficult to sand.

Sorry about the spelling ,I had a good looking spelling teacher in school was to busy watching her to learn how to spell.
Ron
User avatar
By TexasZeke
#1336200
that's ok, still wouldn't have known what it was if you had spelled it right.

looking for something stronger than wood flour?

kevin
User avatar
By bowgarguide
#1336205
No not really just wondering why you would mix something else ( a filler) in to use epoxy as glue. I understand why for filets.
Ron
User avatar
By Pogo
#1336237
So how come Gerald's not replying? This is one area he really knows well.

In the meantime, here are a couple notes from a guru wannabee:

1. Read the tech literature that comes with epoxy and related products. It's dry reading, but there's good stuff in it. West Systems epoxy may be dreadfully expensive, but they give away tons of free literature that explains all sorts of stuff, including this particular topic.

2. Nothing like keeping a microscope around. Examining things like fillers especially can be mighty educational.

3. My understanding of it: Cab-O-Sil, or fumed silica, is like microscopic strands, so they provide a bit of "rebar" effect, if that makes sense (hint: fiberglass cloth in epoxy works the same as rebar in concrete). Microballoons really do look like teensy little glass spheres -- how do they MAKE 'em??? -- and provide no structural benefit; its purpose is to make epoxy take up space. Wood flour, or ultrafine sawdust, falls somewhere in between, and is popular because it's either cheap or completely free. Still need to study up and find out what fairing compound is.

Epoxy can be a glue, but that's only one of its many uses. As a glue, it often needs a little help because it doesn't have much in the way of gap-filling ability, and that's where a filler comes in. When choosing a filler in this case, why not go for the one that adds strength since glue needs to be strong?
User avatar
By bowgarguide
#1336255
Pogo
I think Gerald is at the shindig Randy is putting on, I appreciate the reply makes sense if it is fibers.
Ron
User avatar
By Pogo
#1336262
Light Keeper's Kid wrote:There were no good looking teachers in military school you lucky dog :lol:

Say WHAT?! Man, that doesn't sounds quite right, especially considering the fact that Gerald's at a WEENIE ROAST (thanks, Ron, I'd forgotten about that). :shock:
By Dogpaddlin
#1336318
So how come Gerald's not replying? This is one area he really knows well.


There is no internet at Stubblefield :D
User avatar
By preacher
#1336393
Ron, in all the jillion pages I read online while studying resin and fillers, a few of them said it didn't make the epoxy stronger or weaker, just gave it a better viscosity for using as glue and fillets.
User avatar
By TexasZeke
#1336538
but from my understanding wood flour is fiberus so what would the difference be? The length of the fibers? different strength of fibers, wood compared to silica?

kevin
User avatar
By Pogo
#1336543
Strength of the fibers.

Keep in mind we're talking about pretty small differences that are mostly discernible when goop is used in large quantities, like on power boats, sail boats, etc. I've used nothing but wood flour out of my stationary belt sander as my exclusive filler for quite a few boats, and only recently began using "real" fillers again, and that's mostly so I'll know a little bit about 'em. But I believe that for our purposes, free wood flour works fine, and only begs the question of how much to add, which is only a matter of what you're hoping to accomplish with it. Glue filler? Mustard consistency. Fillets? Peanut butter. Etc., etc.

Also, wood flour being a natural organic material, it's naturally inconsistent, and fumed silica being synthetic, is very consistent. This means thickened epoxy made with fumed silica will "go on" smoother and "creamier" than that made with wood flour. The finer the wood flour, the smoother it'll get. Mix up some thickened epoxy using coarser sawdust, or anything else that strikes your fancy, next time you have some leftover in a cup that's going to waste, maybe try to apply it something disposable, and see what cures out.
User avatar
By gerald
#1336876
Pogo has covered this pretty well. You use fillers to increase viscosity for certain things. Adding filler does not increase "volume" to any noticeable degree. The type of filler DOES affect the strength of the overall joint or use. Fumed silica is the strongest, smoothest, easy to work, very light, and generally white-ish(?). Wood flour is next and is generally the filler most of us can easily obtain and use. Various micro-balloons and other materials are on the list as well, but generally not as strong. When you use less strong, but possibly lighter, fillers you have to increase the size of the fillet to gain the necessary strength. Sometimes a fillet is for cosmetic purposes. Size doesn't matter in that case.
By Iamdamoder
#1336881
Here is a tidbit from the West guy.
http://www.westmarine.com/webapp/wcs/st ... ystems.htm

I can't find the link to the chart I'm looking at in the West book.
West 406 (colloidal silica) gets the highest marks across the range of bonding/filleting applications. Compared to their others(404, 403, 405) You don't want to use Microballoon stuff like 407 / 410 for bonding. The 405, I guess is basically wood flour it is pretty (darker than okume) but does not get as many stars (the chart) as the 406 (colloidal silica/ cabosil whatever).

I think I want 406 with a touch of wood flour for color.
This is just stuff from the book I have not tried it.

oops I'm on the Guru thread
User avatar
By preacher
#1336929
It never fails . . . put something in writing and it turns around and bites you. West says some interesting things including adding strength.


Using Epoxy Resins

Modifying the Epoxy Mixture
Because unmodified epoxy is both expensive and has low viscosity, you frequently add fillers or additives to create the right blend of properties for the job. Fillers are designed to thicken the epoxy mixture and are broadly grouped into two categories: High Density and Low Density.

High Density fillers are used to modify the structural properties of the epoxy by adding strength, bulk or both. Examples include WEST Systems #404 and #406. High density filler mixtures cure to a strong, hard-to-sand plastic useful in structural applications like bonding, filleting and laminating.

Low Density fillers cure to a light, easily-sanded material which is often used for cosmetic or surface applications such as shaping or fairing. Examples include WEST Systems #410 and #407.

Additives alter the physical properties when the epoxy mixture is used in coating applications. Barrier coat additive (#422) improves the effectiveness of the basic epoxy/hardener mixture at resisting moisture penetration. Adding graphite powder (#423) makes coated surfaces slick, which can be used on rudders, centerboards or centerboard trunks. Aluminum powder (#420) can be used to prevent UV deterioration.

Unlike additives and fillers, reinforcing materials are not mixed with the epoxy, but are often used in conjunction with the epoxy mixture to provide additional physical properties.
User avatar
By Hirsch
#1336972
bowgarguide wrote: Sorry about the spelling ,I had a good looking spelling teacher in school was to busy watching her to learn how to spell.
Ron


Buy you books, send you to school and all you want to do is... :lol:
User avatar
By bowgarguide
#1337010
I am going to rephrase this question if I have two pieces of wood I want to glue together,not a fillet ,just two pieces glued together does an additive help any.
Ron
User avatar
By gerald
#1337108
bowgarguide wrote:I am going to rephrase this question if I have two pieces of wood I want to glue together,not a fillet ,just two pieces glued together does an additive help any.
Ron


I will state emphatically that yes I would add a filler for use as glue--primarily to increase the viscosity and gap filling characteristics--not because I want it stronger, though it will be. Laminating epoxy is quite thin and can run away from the joint if you're not careful. You do NOT want to tightly clamp epoxy joints (like wood glue). For goopie and glue I use a thick epoxy and still add filler because it works better. For the purposes of boat building, for the strongest glue where I'm not worried about the color, I'd use fumed silica. Generally I use wood flour of varying colors because I like the color better for the glue lines. Micro balloons are not satisfactory for use as a glue.

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