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Question about epoxy resin chemistry..
Hello everyone.
I am attempting to find a suitable epoxy resin in SE Asia (Thailand specifically) for building a composite airplane. It doesn't appear that any recognized brands are sold here, however there are factories that produce epoxy of all kinds. However, in order to get the correct epoxy I need to know what to ask for. Specifically, my research on the web has led me to conclude that most aviation/aerospace epoxies are Bisphenol-A based resins with an amine based hardener? Is this correct or have I interpreted the data incorrectly? What I am looking for is a very high strength hardner that performs well in humid climates and is oven cured at about 120C/250F. I also need good viscosity for long periods at room temperature. Additionally, I need a room temperature curing epoxy that can cure much quicker but gives me similar strength. As I understand the technology, the resin really isn't that important in the overall equation. Any bisphenol-A resin will generally work. But the choice of hardner is crucial. Can someone help me understand the chemistry here? Should I be looking at an amine based hardner, and if so, which type? Aromatic Amines Aliphatic Amines Cycloaliphatic Amines Boron-Hydride Amines etc. Then there are "modified" versions of each of these, and they also make and sell blends. There are other types of hardners as well, and I don't understand those either. Can anyone tell me what a "normal" aviation grade expoxy resin consists of? What about resources that will help me to understand this so I can make an informed choice. Thanks for any information. Chris |
#3
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Chris wrote:
Hello everyone. I am attempting to find a suitable epoxy resin in SE Asia (Thailand specifically) for building a composite airplane. It doesn't appear that any recognized brands are sold here, however there are factories that produce epoxy of all kinds. However, in order to get the correct epoxy I need to know what to ask for. Specifically, my research on the web has led me to conclude that most aviation/aerospace epoxies are Bisphenol-A based resins with an amine based hardener? Is this correct or have I interpreted the data incorrectly? Chris I'm at the same stage, Chris, except that I'm in the states and still can't sort through all the muss. There are multiple brands that I can choose from. They all say they are the best, and list 100 properties that seem to be important. The newsgroups are full of people saying, "I used brand X, and I liked it!" When questioned, they had never used anything else, and had basically done the inny-minny-mienni-moe roututine out of aircraft spruce. There were some interesting postings in this newsgroup around 1994, which discussed the importance of some strength properties of different formulations, but I don't have any idea how that applies to what's on the market today. To make matters worse, I've started looking at premade panels. FR4 and G-10. One of the other builders just gave me a lead. IL/Norplex manufactures a variety of premade panels, and publishes data sheets on the web. Now there is a load of confusion. I guess the point of this post is the hope that someone out there who has some real information on the different properties and how that interrelate will help both of us. -- http://www.ernest.isa-geek.org/ "Ignorance is mankinds normal state, alleviated by information and experience." Veeduber |
#4
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On Thu, 08 Apr 2004 19:11:05 GMT, Ernest Christley
wrote: Chris wrote: Hello everyone. I am attempting to find a suitable epoxy resin in SE Asia (Thailand specifically) for building a composite airplane. It doesn't appear that any recognized brands are sold here, however there are factories that produce epoxy of all kinds. However, in order to get the correct epoxy I need to know what to ask for. Specifically, my research on the web has led me to conclude that most aviation/aerospace epoxies are Bisphenol-A based resins with an amine based hardener? Is this correct or have I interpreted the data incorrectly? Chris I'm at the same stage, Chris, except that I'm in the states and still can't sort through all the muss. There are multiple brands that I can choose from. They all say they are the best, and list 100 properties that seem to be important. The newsgroups are full of people saying, "I used brand X, and I liked it!" When questioned, they had never used anything else, and had basically done the inny-minny-mienni-moe roututine out of aircraft spruce. There were some interesting postings in this newsgroup around 1994, which discussed the importance of some strength properties of different formulations, but I don't have any idea how that applies to what's on the market today. To make matters worse, I've started looking at premade panels. FR4 and G-10. One of the other builders just gave me a lead. IL/Norplex manufactures a variety of premade panels, and publishes data sheets on the web. Now there is a load of confusion. I guess the point of this post is the hope that someone out there who has some real information on the different properties and how that interrelate will help both of us. Ernest, I'm not sure I understand the problem. Most kits that require fiberglass supply the recommended type of resin. If you are doing something other than buiding a kit, you could just look at what the kits supply and use that, couldn't you? Why is this so difficult? Are you designing your own airplane? Thanks, Corky Scott |
#5
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On Thu, 08 Apr 2004 19:11:05 GMT, Ernest Christley
wrote: Chris wrote: Hello everyone. I am attempting to find a suitable epoxy resin in SE Asia (Thailand specifically) for building a composite airplane. the major strength reducing contaminant for epoxy is moisture. make sure you take humidity into account when doing a layup. ie the lower the humidity the better. btw got a ciba geigy dealer nearby? they have aircraft stuff. Stealth Pilot |
#6
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Corky Scott wrote:
Ernest, I'm not sure I understand the problem. Most kits that require fiberglass supply the recommended type of resin. If you are doing something other than buiding a kit, you could just look at what the kits supply and use that, couldn't you? Why is this so difficult? Are you designing your own airplane? Thanks, Corky Scott Hey, Corky! I believe you were involved in the most informative thread I found as I was searching the archives of this group. Let me see if I can convey a least part of my confusion. The Dyke Delta JD-2 is a plans built craft...ie, no kit. The plans specify that the composite wing skins be laid up on a flat table and then wrapped and riveted to the stainless steel ribs before it is fully cured. I'm at work, so don't have the plans in front of me, but the instruction read something like: The prototype uses polyester vinyl resin. Other types of resins are available. Follow resin manufacturer's instructions. May not be the exact wording, but that is the gist of it. John Dyke has had a lot of problems over the years with the resin continuing to shrink, exposing the weave, etc. So I want to avoid those problems. That's the start of the confusion. Larry LaBeau just completed his Delta a year ago, and had a lot of success using premade panels. Hmmm...get a stronger, pin-hole free skin without all the work, smell, or exposure to hazardous chemicals. Great idea in my book. He bought his panels 6yrs ago. If you look at a manufactures web site, you'll be inundated with choices, all only slightly different. The thread I read here occured in 1994, and it discussed how brittle resins were and that some 'new' developments were making resins tougher vs just harder. It discussed how West Systems was not a good laminating epoxy, even though Aircraft Spruce sells it as a laminating epoxy. In fact, every place you look that sells epoxy says that every formulation is the perfect solution for everything. Just a lot of noise and practically no signal. I go to the EAA meeting and mention "resin system" and really get noise. If you try this, be ready to duck the flak from those supporting epoxy vs vinyl ester vs polyester vinyl vs chicken soup soaked paper napkins. I get the impression that very few know anything other than what their kit specified, and are arguing from the 'my choice must be the best, else I'm an idiot' perspective. I'd like to make these skins once, and not have a lot of regrets in 5yrs. I want to pick the BEST sytem, not just a good system. But as far as I can tell, the stuff that Lowe's has on its shelf is no different than the 'aircraft' epoxies, except in the lower price. I find VERY little difference in the mechanical properties of the different resins, but a LOT of difference in prices. Either I'm missing out on something, or a lot of people are getting taken for a ride. At this point, I'm assuming the former. Where can I find recent information other than sales brochures? More importantly, does it really matter? Is the stuff at Lowe's so much stronger than what's required that it just doesn't make sense to spend more? I forget who said it, but answers are easy. It's asking the right questions that's hard. Right now, I'm at the point of not even knowing if there is a good question to ask. -- http://www.ernest.isa-geek.org/ "Ignorance is mankinds normal state, alleviated by information and experience." Veeduber |
#7
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On Fri, 09 Apr 2004 15:37:51 GMT, Ernest Christley
wrote: Corky Scott wrote: Ernest, I'm not sure I understand the problem. Most kits that require fiberglass supply the recommended type of resin. If you are doing something other than buiding a kit, you could just look at what the kits supply and use that, couldn't you? Why is this so difficult? Are you designing your own airplane? Thanks, Corky Scott Hey, Corky! I believe you were involved in the most informative thread I found as I was searching the archives of this group. Let me see if I can convey a least part of my confusion. The Dyke Delta JD-2 is a plans built craft...ie, no kit. The plans specify that the composite wing skins be laid up on a flat table and then wrapped and riveted to the stainless steel ribs before it is fully cured. I'm at work, so don't have the plans in front of me, but the instruction read something like: The prototype uses polyester vinyl resin. Other types of resins are available. Follow resin manufacturer's instructions. May not be the exact wording, but that is the gist of it. John Dyke has had a lot of problems over the years with the resin continuing to shrink, exposing the weave, etc. So I want to avoid those problems. That's the start of the confusion. Ah, got it. The only suggestion I can make would be to speak to the folks who supply the plans materials and see what type of resin they are now offering. Perhaps it's different from the one originally called for by John Dyke. If that doesn't give you satisfaction, I think I'd speak to the manufacturers of the various resin systems and ask the opinion of the experts there. Explain what it is you are trying to do and why you are asking for their opinion. The covering process sounds complex: you have to allow the cloth to semi cure, and then lay it one such that it bonds in place. Man, that sounds like a narrow window. Saw one of those things zipping by at a Waco fly-in in Ohio back in '93 or so. It was FAST. Corky Scott |
#8
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Corky Scott wrote:
On Fri, 09 Apr 2004 15:37:51 GMT, Ernest Christley wrote: Corky Scott wrote: Ernest, I'm not sure I understand the problem. Most kits that require fiberglass supply the recommended type of resin. If you are doing something other than buiding a kit, you could just look at what the kits supply and use that, couldn't you? Why is this so difficult? Are you designing your own airplane? Thanks, Corky Scott Hey, Corky! I believe you were involved in the most informative thread I found as I was searching the archives of this group. Let me see if I can convey a least part of my confusion. The Dyke Delta JD-2 is a plans built craft...ie, no kit. The plans specify that the composite wing skins be laid up on a flat table and then wrapped and riveted to the stainless steel ribs before it is fully cured. I'm at work, so don't have the plans in front of me, but the instruction read something like: The prototype uses polyester vinyl resin. Other types of resins are available. Follow resin manufacturer's instructions. May not be the exact wording, but that is the gist of it. John Dyke has had a lot of problems over the years with the resin continuing to shrink, exposing the weave, etc. So I want to avoid those problems. That's the start of the confusion. Ah, got it. The only suggestion I can make would be to speak to the folks who supply the plans materials and see what type of resin they are now offering. Perhaps it's different from the one originally called for by John Dyke. If that doesn't give you satisfaction, I think I'd speak to the manufacturers of the various resin systems and ask the opinion of the experts there. Explain what it is you are trying to do and why you are asking for their opinion. The covering process sounds complex: you have to allow the cloth to semi cure, and then lay it one such that it bonds in place. Man, that sounds like a narrow window. Saw one of those things zipping by at a Waco fly-in in Ohio back in '93 or so. It was FAST. Corky Scott Back in "the old days", polyester resin was all that was really available. Not wanting to start the resin wars again, I'll only point out that JD used polyester resin for the Delta skins. But if he were designing this plane today? It would use epoxy resin. And foam cored composite structure - (instead of the welded/brazed steel structure) just the way he originally envisioned it. John was _way_ ahead of his time... Richard |
#9
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On Fri, 09 Apr 2004 15:37:51 GMT, Ernest Christley
wrote: :In fact, every place you look that sells epoxy says that every :formulation is the perfect solution for everything. Just a lot of noise :and practically no signal. I go to the EAA meeting and mention "resin :system" and really get noise. If you try this, be ready to duck the :flak from those supporting epoxy vs vinyl ester vs polyester vinyl vs :chicken soup soaked paper napkins. I get the impression that very few :know anything other than what their kit specified, and are arguing from :the 'my choice must be the best, else I'm an idiot' perspective. Talk to Gary Hunter, of Gary Hunter Composites in Houston, Texas. The last email I have for him is gluegaru (at) earth (dot) net. Another one I have is gary (dot) hunter (at) resins (dot) com but that one is older and my not be good anymore. Do the obvious replacements to despamify. "Gary is an Epoxy Resin Chemist for Shell Chemical Company, with over 26 years experience formulating and using epoxies in various end uses throughout the industry." |
#10
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Me thinks the 'panels' are riveted on semi-cured because in the good ol' days when resins cured they were brittle. These
are simply skins on the wing and they are not adhered via the resin; the resin is supposed to be slightly green to allow it to conform to the airfoil without cracking. Lay out the panels on a big piece of glass and it will be pin hole free when you pull it off. The panel can be trimmed to size while still on the glass. How many layers of what kind of glass are used in the lay-up? How sharp is the tightest bend? -- Dan D. .. "Corky Scott" wrote in message ... On Fri, 09 Apr 2004 15:37:51 GMT, Ernest Christley wrote: Corky Scott wrote: Ernest, I'm not sure I understand the problem. Most kits that require fiberglass supply the recommended type of resin. If you are doing something other than buiding a kit, you could just look at what the kits supply and use that, couldn't you? Why is this so difficult? Are you designing your own airplane? Thanks, Corky Scott Hey, Corky! I believe you were involved in the most informative thread I found as I was searching the archives of this group. Let me see if I can convey a least part of my confusion. The Dyke Delta JD-2 is a plans built craft...ie, no kit. The plans specify that the composite wing skins be laid up on a flat table and then wrapped and riveted to the stainless steel ribs before it is fully cured. I'm at work, so don't have the plans in front of me, but the instruction read something like: The prototype uses polyester vinyl resin. Other types of resins are available. Follow resin manufacturer's instructions. May not be the exact wording, but that is the gist of it. John Dyke has had a lot of problems over the years with the resin continuing to shrink, exposing the weave, etc. So I want to avoid those problems. That's the start of the confusion. Ah, got it. The only suggestion I can make would be to speak to the folks who supply the plans materials and see what type of resin they are now offering. Perhaps it's different from the one originally called for by John Dyke. If that doesn't give you satisfaction, I think I'd speak to the manufacturers of the various resin systems and ask the opinion of the experts there. Explain what it is you are trying to do and why you are asking for their opinion. The covering process sounds complex: you have to allow the cloth to semi cure, and then lay it one such that it bonds in place. Man, that sounds like a narrow window. Saw one of those things zipping by at a Waco fly-in in Ohio back in '93 or so. It was FAST. Corky Scott |
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