Acrylic Bonding Techniques & Aquarium Construction

[phixer]

Hello
Ive seen this topic come up a few times before but the detailed process of actually joining acrylic still seems to be somewhat of a mystery to most people Ive talked too. I think that a detailed technical discussion of this subject would benifit a great many of us and our hobby as a whole, possibly increasing the number of DIYers once people actually know how to do it properly. When bonding two acrylic panels using the two part epoxy method, are the two pieces actually welded/fused/melted together in the same way same way that cementing them does?, i.e capillary method using acrylic cement? Some manufacturers prefer this method to capillary bonding. They say its stronger. I know the process is much different but does the 2 part epoxy actually melt the two separate acrylic panels together into one in the same manner that cementing does? Im asking because I have heard that salt water can attack joints bonded using the capillary method. But if the cement actually fuses the two pieces together molecularly like a weld, how would the joint be any more succeptable or vulnerable to salt water? Is the 2 part epoxy method stronger? Is it because the 2 part method uses an even amount of adhesive producing a more uniform bond where as the capillary method just soaks into the crevices unevenly? I.e uneven WELDING vs even GLUING, wouldnt this defeat one of the atributes of acrylic bonding? Which one is stronger? Should the edges be left rough for the cement to grab on to? like bare metal before primer? If the edges are beveled and finished smooth before joining them then wouldnt the capillary method be stronger because of the molecular bond? I have several large panels to join so the soak method wont work. I will be doing some testing and will pass along what my findings are. If anyone else can contribute please jump in, your input is valuable to our hobby.
Thanks again
Phixer

 

[nytrillium]

i may be wrong.. but the 2 part epoxy is simply a mollecular bond(surface bond/friction) and not a chemical bond like the solvent glues are. I believe that saltwater in the long run could harm a join made with epoxy. On the other hand a joint made with weld-on #4 or #16 would be as impervious as the acrylic itself since ... it is acrylic. Besides over time 2 part epoxy can be very brittle... Like you said, gluing acrylic with solvents is essentially welding(without the addition of extra material) in that it forms a joint that is made up of the same material that you are trying to join. Steel, welded with steel welding rod. Acrylic welded by dissolving part of the acrylic panel in solvent and then the solvent evaporates and the acrylic sets again.
It would seem to me that acrylic bonded using the capilary method or a similar method would be much stronger. Even wiht Weldon 16 that is viscous would probably form a better bond.
Eage to hear other opinions...

 

[phixer]

I was thinking the same thing, if the two part stuff is epoxy I would not trust it for the same reason, epoxy tends to harden over time and with the hard saltwater envioronment it might become brittle. To me this would be a somewhat similar bond as glass (except that silicone is riselent ) it would likely defeat one of the bonusus of an acrylic bond though. Now using acyrlic chips to thicken acrylic cement to a syrupy consistency and then pouring this stuff along the panel, then clamping the other panel to it and quickly wiping off the excess might produce a strong bond. You would probably have to work quick if the drying time is fast and surface to be cemented together is long. But if the edges to be cemented are slightly beveled what good would clamping them do if you are trying to keep the sections at a 90 degree angle, the bevel would have a tendency to make the section tilt inward, even using a jig to keep them square to each other the clamping force would still be exerted along a finer edge which could result in crazing or chipping. I would be inclinded to just let the weight of the panel be enough instead of clamping it, this way you would know that you are exerting an even pressure over the entire surface and could contain it with tape or a peice of wood. Like a dam which an expert plastic fabricator suggested. I recently spoke to a Professional who told me that it is the pressure pushing outward over time that wears the joint out which really made sense to me. Even small factors like a wave machine could take their toll over time. Welded(cemented) joints are stronger but must be uniform in thickness and penetration like a welded bead on metal, it seems like there isnt much difference in the physics of it all between the two when it comes to bonding. The break/leak will occur at the weakest point where the weld is the thinnest, which might explain why the edge should have a slight miter/inside bevel to it. To hold more cement. I guess if someone was really concerend about strong joints and not cosmetics you could cement them while adding a small block of acrylic to strengthen each corner and then frame the tank in a wood trim or plastic time to hide the acryllic blocks in the corners. A strong angle frame around the corners would also help if it could be concealled. An outside angle iron frame would be strong and might be safe if painted and then coated in a resilent material completly isolating it from saltwater intrusion. It would be very unsightly so might have to be hidden by trim. Im certainly no expert and may be way off with my ideas but Im going to experiment a little.
Phixer

 

[nytrillium]

Sounds about right to me....

I always liked the idea of a acrylic tank framed with angle iron. Like you said you would deffinately have to coat it with something really heavy duty likea rhino lining kind of stuff but it would work. Also rather than using an acrylic block you could just run a second bead of weldon 16 (thicker) after you set the joint with a capillary bond.

 

[chipmaker]

Its pretty well straight forward how to bond acrylic...If solvent welded joints are supposedly so weak espeically those made by wicking, then I htink someone needs to make a phone call to the numerous folks and companies that have been doing this for years on end....A solvent welded joint is as or close to being the same strength as the acrylic itself.....To me unless the substrate has sufficient properties to achieve a good super tight bond and perhaps even dissolve and reharden after its setup then surface type adhesives or epoxies would be fine. There are literally hundreds and hundreds of various epoxies out in this world geared to a specific task...and other than some being copies of others sold under a different name, they all have their place......a wicked joint is the same as a joint that was assembled with pins, except the length of wetting the two bonded pieces is reduced timewise, so you may not get as deep of penetration, but I do not think that is a problem if its bonded and reset.......People as a whole seem to think in a narrow vision mindsent.that epoxie is just that epoxie.....and it could not be further than the truth.
I have used somne 2 and three componenet epoxies that actually dissolved some of the parent material during the curing period, and others that did not...Just look up Hysol-Dexter products and see what they have to offer......expensive stuff, extremely short shelf life, but if its used on the recomended parent material then integrity of the joint should not be a problem.....same for any of the solvents like #4 or 6 or even the two part mixes commonly used.....

 

[nytrillium]

I dont disagree with you there. I know there are thousands of different epoxies out there. But I would imagine that the right kind to do what we want here would be more expensive that using a solvent glue to weld the panels. Am i correct?

 

[phixer]

I did some more research and came across an old Time Life book I had, titled "Working with Plastics". It had some pretty good information regarding the two part cement , Im learning that this is probably not the same type of epoxy Im used to though. The book described the two part formula as an acrylic cement (but not an epoxy). The difference being that the acrylic cement is a solvent melting material which melts the two peices together... But isnt a two part glue/adhesive/cement an epoxy?..., I mean you have a resin and a hardner right?..., that makes it an epoxy I thought. It went on to say that the two part stuff is useful for rough-trimmed edges and along joints that could benefit from the reinforcement of an extra fillet of material. It consists of a combination of acrylic resin and a hardner, mixed to a syrupy consistnecy just before use. Unlike solvent cement , this type of acrylic cement actually requires a slight open rather that a closed fitting joint, (which would describe the 15 degree outside bevel across the entire face of the edge). The joint is stronger because its more uniform due to the beveled gap being filled with the thicker cement. What I dont understand though is why not just use the thicker 1 part stuff to begin with and not have to worry about mixing it ? I speculate that some manufacturers use the capillary technique because its faster and does not require beveled edges of the panels being bonded, just mate the two peices toghether and run a bead of solvent cement with a needle applicator, which would probably be fine unless you are dealing with extreme pressures generated by deep tanks over 36" in depth. Because the capillary method simply allows the cement to flow into the crevices I cant see how it bonds them together as uniformly as the thicker stuff does because you know exactly how much your using to fill the beveled gap and because your also building an outside fillet pressing against the edge. I spoke with a tank builder last week who will only use the two part stuff, he says it produces stronger joints.
I agree, Hysol is good stuff, Ive used it for surface repairs on carbon fibre flight control surfaces such as ailerons and trailing edge flaps as long as the damage is within limits, for me Hysol works good for these applications. Dont know if they make solvent cements though, the Hysol Im familar with comes in yellow tear apart packages and is basically just an expensive epoxy. Best regards.
Phixer

 

[nytrillium]

I understand what your saying wiht the cement/epoxy issue. however the epoxy is two chemicals that react to form a new material that hardens. (i think) while the acrylic cement you are referring to most likely contains a solvent and an acrylic like substance that, like you said, ends up looking alot like a thicker one part cement|
I would agree with you that a fillet over the joint would probably be stronger and it would deff. make me feel safer. Where would you buy some of this two part Hysol stuff? It sounds like it may be worth buying. Is it alot more expensive than a bottle/tube of weldon #16? Does it come in small quantities?

 

[chipmaker]

Phixer, the HYSOL your referring to is nothing more than a typical 2 part component epoxy such as Hobby Poxy or Devcon which is commonly available in hobby shops and wally world. Hysol name is confusing as HYSOL-DEXTER makes a heap of adhesives and sealants...I am more than familiar with the yellow foil packs you described, as I must have opened up a million of those packets over the years....We used to call it double bubble..and like I said is just a standard grade polyamimine (sp?) product. I have some sealants here with price tags of $50> for a mere 2 oz. One neat product and we just call it hysol or super snot, is a thick creame colored gel, with a watery lite honey colored catylyst, that sticks to just about anything......glass joints are virtually impossible to get apart without breaking the glass, and I think if it was not for it being messy to work with and such a fast set time it would turn out to be a good material to stick a lot of acrylics and glass together......I stuck some pieces of glass and acrylics on holes that were in a 50 gal reptile tank so I could turn it into a QT for some GF and small koi years ago, using this Hysol Super SNot, and its yet to let its grip go or leak. It cures to a light grey/opaque white color. In the years its been in use it must be inert as I never had problems with fish becoming ill. ANother good sealant for acrylic and glass is the Hysol Polysulphide rubber coating......I have a large tank assembled with that stuff. Its more a coating than a adhesive, but it works super for that job as well..Been in use perhaps 4 years now.....
Fillets are better but really not needed on a solvent welded corner joint made with a solvent based adhesive. Devcon makes a combination 2 part epoxy specifically for plastics and it will soften and melt into plexiglass and polycarbonate. Its easy to use, and comes packed in a siamese syringe for easy measuring. I has a pretty bad smell when uncured, but after curing its not very flexible, and once apllied to acrylic its virtually impossible to get it to peel off and let go...... It is pretty cheap and is readily available in most wal marts and big box stores that carry Devcon products.....bout $3.00 for a total of approximately 4cc. I have a feeling this Devcon 2 part plastics epoxy is similar along the lines of the two part stuff Weldon sells. Its too thick to wick into a joint, but applying it to an edge, then closing up that gap and using your finger to make a fillet out of what squeezes out in the inside corner should provide a super strong joint to an acrylic tank etc........its just not going to dry to a optically clear joint..working time is approx 30 minutes, and full cure within 12 to 24 hours depending on temps. I guess working in structural repair career field in the USAF has me spoiled with all the neat compounds that is used in aerospace applications, unfortunately most of that stuff is pretty pricey or hard to find locally, and in quanitys suitable to hobbyists. It also usually has a pretty definitive shelf life, that we have found out does not pay to exceed if your looking for perfect results.

 

[acrylic51]

Just use the correct solvents to bond acrylic, and 2 part epoxy isn't it!!!!!!!

 

[psusocr1]

weld-on is amazing stuff. i built a 500 gallon tank for my crocs witha crylic and i used wled-on 3 and 16(the thicker stuff) for the bonding, when all was said and done it was time to move from my appartment to my house, so i decided to take the croc cage down. i tried everythign to get those joints to loosin up to putt them apart but NOTHING worked until i cracked the acrylic, i had to saw and cut all the acrylic with dremels. that stuff is AMAZINGLY STRONG.....just my .02 cents

 

[turningtim]

acrylic, psu I just bought some sheet stock and weld-on 4 and 16. I've read the proper way of adhering the acrylic together (pin/wicking). But on my way home I thought how do you apply the #4. Is there a specail syringe that I should use? Can I use a dosing syringe? but will it melt that together?
This is just for an overflow and some baffles.
Thanks
Tim

 

[nytrillium]

Yeah you can use a steel tip medical syringe if you can get your hands on some. You will ony be able to use it once cause it will dissolve the plastic probably. Ebizzle also has "flux bottles" that are plastic bottles with steel syringe tips that would be good for the weldon 4. You can also buy syringes online from some vendors however if they are in the US there is a disclaimer and i think you have to proove that you use them for medical use or something like that.

 

[psusocr1]

hey tim shoot me an email at psusocr@aol.com
the place i use to order my acrylic and also weld-on and appliances sells special syringes(will never melt or clog) , bottle syringes, and great applying and cleanign tools for whatever you can think of in the plastic world. They are VERY cheap and ship VERY quickly. they also have weld-on for an awesome price and you get too choose from alot of diff. sizes!
psusocr@aol.com

 

[chipmaker]

Drop by your local veterinary place and talk to the doc. Odds are he'll give or sell cheap a syringe and needle. Around here we can buy tem in all sizes all day long in farm and feed supplys......A 5cc is ok and so is a 3cc and I have used insulin syringes as well. I owuld not go any larger than a 10 or 12 cc as they get too big to handle for most smaller work. A 60cc with a 18 ga 2" needle sells for 50 cents at the local farmers coop, and the 10-12 cc sizes without a needle sells for about 20 cents each and needles in various sizes go for about a quarter. A needle of 25 ga is fine, but finer will work as will larger, but 25 is a pretty common size but try and find one with a length of about 1" to 1 1/2 long. Weldon will not dissolve the material the syringes are made out of. On some it may swell up the rubber plunger seal but they always go back to normal and can be reused.....Pull the needle tip along the joint, and do not go over the joint after initial fill. It usually winds up clogging up your needle tip.......The typical needles sold for applying solvent all have squared or blunted tips not sharp tips as the typical hypoderic needle has. YoU can file/stone it down for a more blunt end if desired and its probably a good idea as its certainly not needed, but they work fine with the sharp end.
Its a heck of a note when a darn junkie can get free needles to support a habit and a hobbyist with no intentin of shooting up weldon #4 has to get a doctors prescription to buy one to use in a legitimate purpose

 

[acrylic51]

Yeah there is a special applicator to apply the WeldOn 4 and you should be able to get it from your plastics acrylic dealer really cheap....If the needle end clogs which it sometimes will if you go over a seam, just take a lighter real quick to the end of the needle and should open back up.....I must warn that the solvent is flamable, but it's safe to do this because it's a real quick hit with the lighter.......
WeldOn 4 will work perfect....The cure time or setup time is a little slower than the WeldOn 3, but the work the same and are the same consistency......Your on the right track as far as doing your homework as far as pin method, but I'm pretty sure you already know that an important key is to have a level work area.....melevsreefs' site shows a good way of using pin and shim method to get a perfect joint......Trust me it works like a charm...........I take and extra step and wish I had a end joiner to get a mirror finish on my edges, but what I do is make sure all sides are square and take my acrylic file which you can use to scrape, roundover or "V" your edges and get a nice clean finish, and then I wet sand the edges smooth.....It works very good, but is time consuming and most people aren't worried about looks at times.
For you exposed finished edges do the same thing, but take it one step further and flame polish them to give a mirror finish.....You should practice on some scrap for a bit, because it does take a bit to get the hang of how fast to move the torch and such over the material without overheating it and causing bubbles in your edges.....You can't flame polish any edge that is going to be glued due to it affects the gluing process......If you flame polish near a glue seam and it gets to warm you will hear a crackle sound from that as well!!!!!
Hope this helps a bit

 

[phixer]

Chipmaker...., double bubble, yeah we call it that too. Are you still on active duty? Im in the USN. In my earlier years I was a structural mechanic working on environmental control systems, ejection seats, oxygen systems and canopies so I got to work with acrylic in varying degrees. More of a management position now I suppose. The two part Weld-on product is Weld on # 42. I found a small bit of information on the SanDiego plastics website describing its use. Tomorrow I will be placing an order for the acrylic and would like to know if anyone has any insight on Polycast acrylic. The military uses a derivative of polycast acrylic for aircraft canopies. I thought that was cool. Im ordering a slightly different type though, Polycast GP. Has anyone had any experience with this brand? Id like to know how it compaires to Acrylite or Plexiglass or if they are all basically the same.
NYTrillium, double bubble Hysol is really nothing special, you shouldnt have any problem finding it on the web. It is really the same stuff as general purpose epoxy sold in hardware stores. You might be better off just using standard epoxy for general applications not bonding acrylic.
We also use PR 1750 and 8802 quite frequently, this stuff is nasty but will bond damn near anything. Sticky as hell and will not come off clothing. Even Spock could not break it. Its ugly, toxic as hell when wet, chemically repellent and works very well for aircraft applications bonding shrouds and boots. I wouldnt use it near fish though. Anyhow back to the subject. I took a field trip today to check out an aquarium at the Bass Pro shops outlet store that opened up where the old Stapleton airport used to be, they have a huge tank housing freshwater game fish that consists of two panels about 10FT long and 5 FT tall joined together in the middle. The seam is all but invisible, who ever built this tank did an exceptional job on this seam. I tried to talk to someone about its construction but most of the folks there didnt know anything. The acrylic must have been between 3-4 inches thick, it was crystal clear. Im trying to find out who made this tank so I can ask a few questions. It looked like the work of Reynolds because of its size. I should take some pictures.
Phixer

 

[chipmaker]

Phixer...I use GP grade for most of my stuff....I got tons of it for free so weather its the proper stuff or not, I can't say, but IIRC its what was recomended by folks on another forum. MIne is cyro (sp?) GP
Nope no longer on active duty. I hung up my hat back in 2002 with a total of 32 years active duty spit up between US Army and the USAF...I started off as infanty /armor....then went helicopter, then transitioned to the USAF as a Mechanical Accessory troop (esentially the same jobs as yu list, environmental systems, egress, control surface rigging etc etc, and later on became fabricatin section super which had the structural repair shops to contend with. which included NDI, Welding, machine and sheetmetal and fabric / textiles..More than familiar with 8802 and PR1750. I used the PR 1750 B 1/2 to make a tank about 8 years ago and its still leak free. I made it with pieces of 3/8 and 1/2" plate glass I scrounged and it also has some acrylic in it, and the PR sticks em all together great.
Speaking of Pr 1750 and 8802, I have some Makrolon acrylic that is bullet resistent stuff about 1" thick that I wanted to make into a tank, but chemical bonding is not a doable thing since it will make it delaminate, so I am told, so maybe i need to give those aerospace sealants a try on that makrolon stuff. I sure do not need bullet resistent glazing in my shop / house, and its just setting there unused. Gonna have to do some experimenting with it and 8802 and 1750

 

[acrylic51]

I'm pretty sure the bullet proof acrylic you have can be bonded, but not actually sure if it would be water tight.....I built a reptile enclosure for a friend out of that stuff and it's highly scratch resistant as well......In order to bond the stuff the surface area that is to be bonded needs to be scuffed really good through the top thin layer of material on both pieces to be bonded to be glued and to hold....Again I never water tested it before, but can be bonded like regular acrylic just a little more tedious

 

[mr.125]

AWSOME THREAD!!!
Thanks for all the info guys!!!! Im am goin to start to experiment!