Return-Path: Received: from [65.33.166.181] (account marv@lancaironline.net) by logan.com (CommuniGate Pro WebUser 4.2) with HTTP id 373571 for lml@lancaironline.net; Sat, 21 Aug 2004 15:53:28 -0400 From: "Marvin Kaye" Subject: Re: resin heat distortion temps/surface temps of aircraft/Hysol replacements To: lml X-Mailer: CommuniGate Pro WebUser Interface v.4.2 Date: Sat, 21 Aug 2004 15:53:28 -0400 Message-ID: In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format="flowed" Content-Transfer-Encoding: 8bit Posted for "Dan Newland" : I said awhile back I was going to get some data for the LML aout surface temperatures of aircraft outdoors, so here it is on Acrobat. After the posting asking about temps, I called up my good friend and old boss Andy Marshall to see if he still had the table of data. He said "Sure, do you have my book?"...Duh... Yeah, he's given me all six editions since it came out. This was scanned from it, "Composite Basics". It is an excellent book, very readable and filled with "How to's" and "Where to go for's". Plus a few "And the whole thing got screwed up when they fogot to..." It is even used as a college text in some university engineering programs. You can get it from Aircraft Spruce and the EAA bookstore I think. Andy used to ship and sell them from his house to but I'll have to ask if he still does that or whether it's strictly through stores now . I also said I was going to do some research on the replacement adhesive for the old Hysol 9339. A guy I work with on our spacecraft projects is the former QC director of Dexter Hysol and worked with this (and other adhesives) for years. I asked him about the Hysol and he in turn got in touch with some of his old buds that are still there. The new stuff is Hysol 9360. It appears to be better in elevated temperature performance by about 20 degrees than the old 9339. It is available in qts. and also in ready mix tubes. I am now checking the archives of Hysol (Loctite) to see exactly how comparable they are and will get back with real data I will get back with the real data because until I see numbers, I won't really know and I would expect some other differences. I am particularly interested in various cure times so people in Arizona in the Summer or Minnesota in the Fall can get the correct forulation for their needs. Many base resins can have a whole family of hardeners that when cured, have similar performance but have different working times. And don't go to the general directory at Hysol to ask for the equivilent adhesives, the people on the computer or phone line had their brains die but their body hasn't found out yet. The Hysol we use is terribly expensive but oddly, in many Aerospace cases is identical to some of their industrial adhesives. In fact, many aerospace and industrial adhesives are taken from the same batch but the aircraft adhesives cost 5X or more of the industrial version. While it is easy to say this is another example of a consumer rip-off like the $500 toilet seat, I can assure you that in aerospace, the documentation is typically more expensive by far than the parts. And no, there isn't an industrial grade of the 9360, I checked because I didn't want to pay their usual "Aerospace rip-off prices." Ooops! One thing I want to re-emphasize is that while there is nothing wrong with Jeffco, it is NOT the same as Hysol. All of the claims that Jeffco with flox, or WEST System and flox, etc are "just as good as Hysol" MAY be correct, but PROBABLY are not. More likely, they may be ADEQUATE and you won't die testing an un-proved theory. Even if the adhesion were similar, adding thixotrope with outsophisticated equipment would mean every batch would be different in wet-out and flow. Jeffco is a general purpose room temp. cure epoxy, it is not designed as a bonding adhesive! It sticks well but a bonding adhesive would probably adhere much better. An analogy is if you said you made your airplane out of metal, it wouldn't tell and engineer or metallurgist much. Well, neither does saying "epoxy" since the physical properties from one to the next may be orders of magnitude different. And price does not necissarily guarantee performance since an adhesive designed to give elevated temperature performance might be too brittle for normal applications. Or an adhesive designed for high bond strength give poor wet-out in a laminate. It is not necissarily bad, just designed to perform best in a certain area that if you are not aware, could be differnt than you intended. A good example of two extremes of bonding performance are an experiment I did using G-10 solid glass/epoxy laminate. I prepped some samples for bonding with WEST system epoxy and another with Applied Poleramic thixotropic bonding adhesive. The WEST (pretty similar to JEFFCO), broke off pretty easily from the bond line (adhesive failure) using a simple wedge test for peel adhesion. The Applied Poleramic epoxy adhesive CAUSED THE LAMINATES TO SPLIT BEFORE THE BOND DID! So do not EVER believe that the term "epoxy" means the same thing for all applications. I use a lot of WEST System laminating epoxy, a lot of toughened laminating epoxy, a lot of toughened adhesives and a lot of toughened adhesives with high Tg temperatures. Not one of them are "bad", but some may not be as good as others for what I need. If you are working on a really CRITICAL part and you need to be assured of maximum adhesion, you should be using better grades of adhesive. By better I mean higher peel strength, higher impact strength, higher tensile or compressive strength, higher tensile and compressive modulus, and VERY IMPORTANTLY perhaps, higher Heat Distortion Temperature (HDT) which is related but not identical to glass transition temperature (Tg). But you need to figure out which properties you need to have improved. The history of Lancairs is such that the materials called out are generally pretty good since we seem to have few structural failures, but that doesn't mean for a few extra bucks we couldn't improve our safety factor and fatigue resistance. Or possibly in case of an accident, stop the damage in a smaller area. Many manufacturers of general purpose adhesives also make more advanced formulations. In fact, Jeffco makes its own brand of toughened adhesive systems and WEST also has higher performance epoxies, (their ProSet epoxy line). There are some really good epoxies out there, but for those that have read my postings before, you know that I like Applied Poleramic. Partly it's because they sell smaller quantities. But also, Rich Molton is the owner of Applied Poleramic and former head chemist at Hexcell where he designed many of their high performance epoxies. I like the ability to reach the person that really KNOWS what he's doing, not a salesperson that can only quote out of the literature. Rich and Doyle (the alter ego) watch their product being made daily so I know the President is aware of everything going on in the plant. It isn't big but it is very good. The phone number is (707 ) 747-6738. Next door to them is YLA Inc. that manufacture high performance pre-pregs so it's a little cottage industry there in Benecia, Ca. And there are certainly other good manufacturers out there if you want to do some research. For that matter, carbon fiber is similar to the generic term "epoxy" in that it is descriptive of the molecule, not the finished properties of the fabric. Some carbon can be had for as little as $12.00/lb (33 million modulus, i.e. 3 x as 'stiff' as fiberglass) and yet I've also worked with $4500/lb carbon that is 120 million modulus, (11 times as resistant to stretch as glass). And the strength was about twice, also. One characteristic of many of these higher performance caron fibers is their NEGATIVE coefficient of expansion. That means that when you heat it up, unlike almost all other materials, it actually shrinks in heat, or in the case of the Aamoco carbon I was just talking about, it has zero Ct. This makes it ideal for satellite antenna and camera mounts since going in and out of the sun in the Earth's shadow doesn't cause it to jump. Well, that's enough from me which is too much for most. Give a holler if I can help, I do have a lot of materials and contacts. Dan Newland Application engineer Orcon Corporation 1570 Atlantic Street Union City, California 94587 phone: (510) 476-2150 cell: (510) 290-6885 fax: (510) 489-6702 [The PDF file sent by Dan with this post has been uploaded to the "Materials & Supplies" page in the Attachments area on the LML website. ]