Surface reatment for gluing?

I thought Silane was nasty stuff.

George H.

Den tirsdag den 10. juni 2014 20.23.53 UTC+2 skrev snipped-for-privacy@gmail.com:

etch with NaOH ?

-Lasse

If it's the same stuff I know about, it's not silane, it's hexamethyldisilazone (HMDS). Silane is pyrophoric.

Cheers

Phil Hobbs

Alodyne or Forest Product Labs treatment for aluminum bonding.

Dan

If I couldn't raise the mechanical engineers that I used to work with who often specified "glue and screw" joints between aluminum parts, I'd get on the web and see what 3M and Locktite recommend. If anyone knows how to glue stuff, those two should be it.

Sandblast the surface?

For some plastics, plasma treatment works wonders.

Thanks for all the responses. (I am using 'silane' to cover for all the derivatives. Is the hex stuff widely sold anywhere?)

One approach I didn't mention is to tumble or vibrate the pieces in ceramic abrasive media or sand. This is done in water, to which you can add your favorite chemistry. A must is to add "Lemishine," which is citric acid. This prevents re-deposition of debris. A drop of detergent good also.

I have several vibratory finishers (HF), a tumbler, and a cement mixer I adapted to a tumbler.

This technique is very handy for finishing 100s or 1000s of parts.

Trick commonly spoken of on RCM: wet the sandpaper with epoxy and sand it "wet" that way. Guess you could add acetone to make that easier. Wipe off the crud, butter it up again, clamp and wait.

Or maybe even leave the crud in the joint as filler. Metal filings aren't really going to weaken it, and broken off sandpaper grains might serve to space the joint (epoxy is strongest in a just-thick-enough layer, a few thousandths of an inch supposedly).

Tim

-- Seven Transistor Labs Electrical Engineering Consultation Website:

Boeing and Airbus too, but they might not tell you how.

"Adhesive Technology: Surface Preparation Techniques on Aluminum"

I use an acid wash for removing the oxide layer, and acetone to remove the grease. Just about any acid, including vinegar, will work. Dilute HCL will etch the surface in order to give you a larger surface area for better adhesion. Brushing with a stainless wire brush will also gouge the surface in much the same manner. A commercial aluminum welding cleaner might be better. They add some kind of wax to the acid to coat the surface to prevent the oxide layer from reforming. The heat of the TIG welder then vaporizes the wax allowing welding to the hopefully oxide free aluminum surface. Something similar could be contrived for gluing using a volatile organic solvent (acetone) to remove the wax.

Thanks Jeff - 171 pages! I will read. jb

thanks - this wet sanding may stop the oxidation process.

FYI "silane" is one of those generic terms which vaguely means practically any derivative of SiH4 - There are about 300 - Dow Corning has a section on silanes which lists 100 or so. Many are good for surface treatment, and each has different surface characteristic. Attached groups include alkanes, vinyl, epoxy, OH, Cl, F, amines - you name it. Even peptide synthesis, linkages to antibodies, etc.

Wikipedia is in error on that, though they admit the term refers to several other derivatives. (should be 100's).

I don't think you want the water, soaking and or cleaning in alcohol would be better.

I worked at a company that made piezo transducers, bonded ceramic (pzt8) to aluminum. After lapping the two together with a fine grit compound, the tech cleaned with acetone and then immediately with alcohol. The alcohol was used to remove water that condensed when the acetone evaporated. Yes, the alcohol cooled when it evaporated, but that was what worked for him. We used a glue that the semiconductor industry used in IC fabrication. It was a gauze impregnated with a heat activated epoxy. ISTR we applied 20 psi at 180*F for less than an hour. The head honcho always wanted a glue without the gauze, it caused inefficiency in our transducers. The bond withstood very high Gs. Mikek

But allow me to talk on a bit on this subject. I'll try to be concise.

Precise chemical nomenclature is actually a sort of intellectual battle that went on for 100 years in organic chemistry,medical science, and physiology. In general, scientific types like precise terminology.

But,, as an anecdote, Szent-Gyorgi the discoverer of Vitamin C, also discoveed the proanthocyanidins. Vitamin C actually will not cure scurvy unless accompanied by OPC's. But Szent-Gyorgi realized the opc's were a diverse group, differing in structure and also polymerization number. Yet most were good for health, and even though they are in maybe 100 foods, they vary in the specifics. So he applied to the international vitamin commission to get them sanctified as "vitamin P." This body was ruled by German chemists, who turned him down based on too much diversity.

So the epistemological conflict between precise and broad thinking had this result. And in general, a specific thing hypnotizes scientists. For example, Pasteur and Koh's germ theory of disease was definite and alo portrayed disease as an alien enemy. Everything became a germ.