Full Version: Acrylic Question
From: gt350ed [#1]
9 Feb 2005
To: ALL
Howdy ALL!!
I have a question regarding glue-up of acrylic awards. Although I have become proficient at bonding sand-carved glass or crystal such that there are no air bubbles, etc., I cannot seem to bond acrylic pieces and acheive a completley clear joint. I consistently have varying degrees of what appears as a "mirror" smear. I use Weld-On which is, of course, almost like water when compared to what we use for glass bonding.
I would be grateful for any feedback regarding tips for acheiving a clear bond.
Thanks.
From: Engravin' Dave (DATAKES) [#2]
10 Feb 2005
To: gt350ed [#1] 10 Feb 2005
Ed,
Here is a link to a discussion on that subject.
http://www.engravingetc.org/forum/?msg=209.1
What type of applicator do you use, hypodermic syringe or squeeze-type bottle?
From: Rodney Gold (RODNEY_GOLD) [#3]
10 Feb 2005
To: gt350ed [#1] 10 Feb 2005
Hiya , we do a lot of pex fabrication
Its a pretty complex subject but here goes. You get 2 types of glues , one that is actually liquid perspex (to put it simply) and others that are merely solvents that melt the acrylic together.
The glue you use depends on the joint you want and its properties. The usual suspects like cloroform , ether , methyl chloride are not at all good choices. Acrylic has an inherent problem and that is stress and that is introduced by poor machining and heat (lasers are the worst here) and using those type solvents without stress relieving the acrylic is a disaster as you get stress cracks developing at the bond , worst of all , sometimes these dont happen for ages and suddenly appear. Extruded (the cheaper stuff) is far more susceptible to this than cast. Be that as it may , there are very specific glues like Tensol (dunno if they sell it in the USA) or products from Degussa (excellent stuff) that are meant for each type of perspex and for various types of bond. If you glue with the correct stuff the bond is often stronger than the pex itself. Your edge quality will determine the bond. If for example you dont have a diamond polished edge which is perfectly flat and you try bond a plaque with a rougher edge to a base with something like chloroform or a flash type "melting"glue , you will get bubbles and a visible glue bond as it cant possibly fill in the microgrooves of a sawn or routed edge and the bond area changes the diffraction of the light. If you had to use a 2 part viscous type glue , a "filler"glue that contains pex , it will fill in everything and you will get a crystal clear joint. The subject here is vast but just about EVERY 1/2 decent pex supplier will have books on how to work and machine/glue pex , Degussa (dunno what they called in the USA) has a cd out with a comprehensive guide to fabricating , the right tools etc. Thing is , there is a huge amount of bad info out there re this subject and a lot of "we always done it this way" type stuff and albeit it might do , it doesnt do well. Our local suppliers often have workshops re this and when I first went I was one of those that "always did it that way and it worked for me" types. the results the demonstrators got convinced me otherwise. You should never see a perspex bond and a bond should be exceptionally strong and all it takes is to use the right stuff , you don't have to be an expert to get expert results.
http://www.roehm.de/en/plexiglas?content=/en/plexiglas/stage
is a good place to start
and go to their download sections and hit adhesives , ther DL the tech specs of the various adhesive products (pdf) files and you will see the various applications and effects of using them.
Do a google search for "tensol glues" lots of useful links come up.
Regards
From: Rodney Gold (RODNEY_GOLD) [#4]
10 Feb 2005
To: Rodney Gold (RODNEY_GOLD) [#3] 10 Feb 2005
Heres another link thats pretty useful
http://website.lineone.net/~mike.bissett/advice.htm#cementing
From: gt350ed [#5]
10 Feb 2005
To: Engravin' Dave (DATAKES) [#2] 11 Feb 2005
Thanks for the link, David. To answer your question, although I have both a syringe and the squeeze bottle, I opted to use the squeeze bottle. I'm sure that's part of my problem--not enough control of the solvent "flow".
I was particularly intrigued by Harvey's response to the inquiry addressed in the link you provided. He suggested making use of capillary action by simply using the syringe presumably at the outside of the joint formed by the two joined pieces.
So, if I have a base and a vertical piece to be joined, does this mean that I could just put the two pieces into position, squirt the syringe around the outer edge of the joint, and the rest would take care of itself--namely, I would have a strong bond with no visible telltale solvent "smear"?
From: gt350ed [#6]
10 Feb 2005
To: Rodney Gold (RODNEY_GOLD) [#3] 10 Feb 2005
Rodney: Thank you for the technical response. I'll have to read it more than once to fully digest it, but I'm appreciative of your taking the time to enlighten me.
As for the brands that you mentioned, I have no idea as to an equivalent product here in the States. For the moment, I'm using "Weld-on", an acrylic solvent. Presumably, this is the correct stuff since it is coming from my acrylic awards suppliers.
As for the maching of the piece I was most recently working on, whether "diamond" polished I have no idea, but both surfaces were highly polished and as smooth as glass to the naked eye. Nevertheless, my application "technique" is likely faulty and is giving me far less than a "crystal clear joint".
Thanks, also, for the links. I'll investigate and study them.
From: Rallyguy [#7]
11 Feb 2005
To: gt350ed [#5] 11 Feb 2005
Hi Ed,
If you positioned the base and piece you intend to adhere in their final location prior to putting the solvent into the joint, you would have capilary action carry the solvent into the joint. The downside is that there would be air bubbles that wouldn't be escape. If you slightly angle the piece you are attaching, place the solvent material along the joint where the pieces touch, apply solvent, and then rock the piece into position, you will have a bubble free joint. Angling the piece allows all the air to escape, whereas basic capilary action alone does not. It takes practice to get the proper amount of solvent in the joint, so be ready to get a feel for the amount of solvent on the length of joint and total area you need to bond.
Hope this helps,
Brian G.
From: Harvey only (HARVEY-ONLY) [#8]
11 Feb 2005
To: gt350ed [#5] 11 Feb 2005
I am not sure how old the reply of mine was that you saw. I have switched to tilting the piece backwards and applying a small puddle then rocking into place. It may not always be bubble free but is a great improvement.
The perfection way is to place a sponge in a container and lay toothpicks over it and saturate with solvent. Hold the bottom of the piece on it for about 30 seconds and then rock it into place. That uses an enormous amount of solvent due to evaporation.
This thread has reminded me to do an experiment that I forgot about. I have used PVC pipe joint compound, both thick and thin formulations for badge back welding in an emergency, and it worked well. I need to try it on awards and see it it works better. I usually have scrap around from making awards.[Since my laser I have gone to multi-layer snap on bases a lot, no solvent.]
Message 798.9 was deleted
From: Rodney Gold (RODNEY_GOLD) [#10]
11 Feb 2005
To: logojohn [#9] 13 Feb 2005