Amazon epoxy vs brand name epoxy?

How much stronger and how much better is the adhesion for a higher quality epoxy such as west system or totalboat vs cheap epoxy from amazon?

I recently used some of the amazon stuff to build a custom evaporative cooling unit for my greenhouse. It seemed to adhere extremely well and the 1/2" radius fillets were hard as a rock, but a couple of them cracked down the middle. They were made with silica filler. I sanded them down and made much larger fillets with silica and wood fiber and all is good now.

Which brings me to the question, would adding milled glass fiber or some other kind of fibrous filler prevent cracking? What other fillers prevent cracking and improve the overall strength of the finished product, without adversely affecting bonding strength?

Is a more flexible epoxy a good solution for things that may thermally expand and contract?

What is the impact of adding microspheres on the strength and bonding?

 

I'm not an expert on resisns and can't say what caused your cracking. That said, I would never buy epoxy on Amazon.

I don't know what epoxy you were using, and I guess you don't either! I would be very suspicious of anything purchased through Amazon. Who knows how long the products have been on the shelf, in what temps., and from where they were sourced. It doesn't seem worth the time and effort put in to work hard on a project and have it fail, just to save a few $$ on cheap materials.

There are suppliers of resins that are not name branded, but still provide consistent quality, without buying a product at a retail store. I don't know where you are located, but I've used US Composites as a supplier for many years:
Fiberglass , Epoxy , Composites, Carbon Fiber - U.S. Composites, Inc. https://www.uscomposites.com/

 

It depends on what you are using the epoxy for. However, Amazon won't have the tech support of a reputable epoxy brand.

 

You are right, I have no idea where the epoxy came from or how it was treated. Even though I had a problem I was impressed with the epoxy considering how cheap it was. I will be using epoxy for many more applications now.

Generally in my handyman work I try and stay away from crappy materials and products, but it is becoming increasingly difficult to find anything worth a damn, even if you are willing to pay for it. And I've had too many experiences now where I chose the more expensive product only to have problems with it, whereas some of the cheaper solutions worked out better in the long run. Hard to know what to believe anymore, and whether a reputation is deserved.

I'm familiar with US composites, I've been considering using them, glad to hear another recommendation.

 

So you can actually talk to a knowledgeable human being with west system or total boat?

 

I have never used total boat. West System has a toll free technical support number. They also have books with information on their products and building techniques.

 

I have actually talked to West System support, so yes real human beings.
My last Ebay batch of 2:1 low blush, low cost clear has a very slow cure time, still soft after a couple days and takes a week to reach full strength at moderate temps according to their technical support. My previous 'surfboard' 2:1 clears, 3 different brands, were hard enough to sand same day or next day.
I have some US Composites 4:1 that is working fine. I have not called them for tech support.

 

No judgement here! God knows I've used all kinds of cheap materials for projects over the years. There's also a difference in work being done for a customer, vs yourself.

Did you know you can use wheat flour as an epoxy filler? Pretty cheap, and gluten is strong stuff! Dunno if the bugs like it though...

 

I'm not aware of a source of technical data for this. I looked through the Gougeon Bros. book and could only find technical data concerning laminating information but not for filler material. Maybe it's there if you want to dig deeper. Let us know if you discover some.

I did come across this video, which may scratch your itch a bit:
"We show how the addition of a wide range of materials can improve the properties of epoxy adhesives"

 

Not knowing who actually makes the epoxy or what products pros use I stick to known names. As I do not have a good source locally, I buy on Amazon or at Duckworks. On Amazon, Ebay, etc. one always needs to be wary of counterfeit product.
West Systems, Total Boat and System Three all work for me. Somewhere I read Raka was a less expensive option with good enough performance to match. I'd be happy to be corrected by someone with actual experience with it.
.

 

Epoxy is a category, not a single material. Amazon is a convenient, if not always reputable source for many things. Amazon Brand-X is a risky business.

It sounds like you may have a situation where you are dealing with differential expansion, so you need an adhesive that can give a little as the parts move. Rigid fillers might not help there. West's standard epoxy is more brittle than some of their competition, which is one of the reasons that they introduced G-Flex, which is a toughened epoxy. System 3 has similar G-2 and T-88. There are others out there, but these I know. I would try any one of them. If you want to spend some money, 3M EC2216 comes to mind. Excellent heat and fuel resistance, at a price. The difference between EC2216 and 2216 is that EC passed a NASA outgassing test for high reliability and space craft applications, so don't worry about the EC if you find plain 3M 2216.

For Tops, about the extremely slow cure. I had the same problem with MAS slow. It worked much better when stirred 2 minutes longer than was reasonable for anything else. Worth a shot if you still have some, but I wouldn't buy more of the Amazon stuff. Raka slow has a long pot life, but it did cure hard reasonably quickly once it started to set up. Having had a bad experience with MAS, I always stir slow hardener longer, so I can't say if the stirring problem is limited to MAS.

Milehog, I can't make you happy with a gratuitous correction. Raka worked well on my latest repair. I have worked with some non-profit boat building programs. It has been observed that the best epoxy to use is the last one donated. They were all name brands and the only drawback was that you had to be careful of the different mix ratios and match to mixing pumps to the brand on hand. There are subtle differences in handling and performance, so switching brands may require something of a learning curve. Edit: I looked at the link again and think I should comment that Raka may have changed formulation in the last 24 years, I did not find it slow to cure recently.

 

Hi,

First of all, the majority of the epoxies sold on Amazon are decorative casting epoxies, which are NOT intended for boat building. They do not
have the required strength and the durability over time. In many cases they will not even have a TDS (Technical Data Sheet)
where their mechanical properties can be checked.

Preferably, a dedicated marine epoxy or equivalent should be used. You can use West System epoxy as the benchmark for specifications
when looking at an epoxy. I am attaching a table I did for another topic. Notice how the cheapest epoxy is also 30% less strong.

 

Thank you for your inputs. Expensive stuff it is for future critical applications.

 

Easy to work out. Buy a jug and do some tests with some scraps (which everyone should be doing anyway).

I would imagine modern epoxy is plenty strong enough to hold wood together regardless of the source. Short or long cure times may not be suitable for production work but may for personal use - hence the tests. I have only used Raka so I can't speak from personal experience.

 

Not really. There are several types of epoxies with very different characteristics. Within each type there are also different stiffnessess. Further, the adhesion properties vary too. There are other properties, like maximum temperature, moisture resistance, chemical compatibility, etc. that are important depending on the application.