Adhesive differences between epoxy brands

I have two brands of laminating Epoxy, one expensive, one cheap. I have found that the cheap one does one hell of a job when laminating a new part but when using it as glue to cured epoxy or polyester it fails miserably. The prepwork has been done by the book in all cases. The expensive one does a good job at both.
What could be the cause that makes an epoxy unusable as glue?

 

One of Our better epoxy goo-rus recently passed away. You will need to provide some very specific chemistry info on the two epoxies. It might be the epoxy formulation itself, or it might be related to fillers, wetting agents, solvents, anti air entrainment agents or viscosity modifiers added to the product. The best thing is to call the manufacturer and talk to their tech people. For all we know, they added a release agent to purposely get it to not stick.

Wikipedia has a good article on Epoxy. It's worth reading through it before calling the manufacturers.

 

I get it "goo" ( sticky Epoxy ) - ru As in Guru.
That's a classic, that needs to be preserved in history.

Did you just think of that, or did I miss the original memo ?

 

PAR would have gotten a real kick out of that.

I too have noticed the same thing and so have gone back to using System Three or West. The cheap stuff just isn't as sticky. Plus I have had fewer problems with bubbling and cure times. In other words, it's worth they extra bucks.

 

Used the cheapest, all solid epoxy I could get, epon 828, $25 a gallon in bulk. It is also the tackiest, most pure form of resin, undiluted and quite thixothropic.

For adhesive/laminating it worked excellent as well as adhering to itself once its sanded. There are even areas inside at plywood bulkheads that will be finished over that were a few years ago first built and exposed to light (no cloth), coated right over, and 2 years later it still holding and scratch resistent.

For wetting out it needs either reactive diluent added in smaller proportion or nonylphenol in greater amounts which contrary to some, is an excellent additive for marine applications, it actually reduces water absorbation rates in cured epoxy however, I think it has formaldhyde so safe handling which should be done anyways is even more important.

Been using Raka for a some glueing and find it satisfactory and once sanded to properly adhere

 

When it comes to strength of epoxies it all comes down to raw materials used to make the epoxy. Buy a good name brand and it will never fail you. Buy a off brand and it may cause majior issues for you down the road.

 

see comparing maine epoxies at epoxylink.com click on link # 19

 

I used a 10 minute epoxy to repair oar blade tips (Z-poxy sold to aeromodellers). After a few hours use the repair came apart. Tried again with UK Epoxy Resins ( a brand); still ok after a week, many hours, of rowing. In this case, it might indicate that fast setting resins are not so adhesive.