Epoxy vs THIXO
- Thread starter LVW
- Start date
Tops
Mildly Thixotropic
"Thixo is a high-strength, two-part epoxy adhesive system that comes in a convenient cartridge. Dispense a bead of thickened, structural epoxy perfect for bonding, sealing, and filling jobs. Included mixing tips ensure perfect resin to hardener ratio. 185 ML cartridge fits all standard caulk guns."-TotalBoat
I have never used THIXO (it sounds handy) but have used the thixotropic (there's a vocabulary word) additive fumed silica to keep regular epoxy from slumping and hollow glass spheres to make it into a more lightweight sanding filler. For fillets under glass reinforcement, I have used 1 part mixed epoxy, 1 part fumed silica, and 2 parts glass spheres (all by volume, an old MAS epoxy video formula). I have had less success with adding homemade chopeed-up glass fibers, I should probably get some pre-milled ones in a jar for the cases that would benefit from it.
If what you are doing is working then no worries.
I have never used THIXO (it sounds handy) but have used the thixotropic (there's a vocabulary word) additive fumed silica to keep regular epoxy from slumping and hollow glass spheres to make it into a more lightweight sanding filler. For fillets under glass reinforcement, I have used 1 part mixed epoxy, 1 part fumed silica, and 2 parts glass spheres (all by volume, an old MAS epoxy video formula). I have had less success with adding homemade chopeed-up glass fibers, I should probably get some pre-milled ones in a jar for the cases that would benefit from it.
If what you are doing is working then no worries.
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Mama H Chicago
Mother of sailboats
My understanding is the thickened Thixo is more for gluing things together, filling gaps, and such. Plain old epoxy is best for wetting down fiberglass, building up thin layers of such for repairs. I’m still learning, but my thought is that unless you add fiberglass cloth or matting or a filler fiber like 404, epoxy alone would only be really for sealing, not repairing.I've been using the two interchangably in wood repairs. (Like repairing splits in wood rudders and daggerboards).
Now I'm thinking that's not such a good idea!
Epoxy is like rum, you can use it straight or add stuff to it to get the desired effect.
The epoxy resin base is the starting point, then you add your choice of hardeners to get it to heat up and cure from a liquid to a solid. Fast, medium, slow, ultra slow...the hotter your air temps are the slower we want it to cure.
To the resin/hardener we can decide if we need more of a harder, stronger structural adhesive or a softer fairing compound.
Where folks run into trouble is using epoxy or other adhesives on wood, especially raw wood like a split rudder. The wood grain needs to be sealed to the point where it stops soaking in adhesives. Straight epoxy is a good way, several coats until it is soaked in. Then do the final fastening with a thickened epoxy to fill in all of the tiny nooks and crannies in the joint. Even with THIXO thickened epoxy adhesive we know it will soak in a bit, sucking the adhesive into the grain and the joint. So we leave a little extra during application with that in mind.
Soaking in would NOT be a factor when sealing up a fiberglass joint, but straight epoxy running out of the joint could be, so that's why we use thickened epoxy. THIXO is the right consistency for that repair.
The epoxy resin base is the starting point, then you add your choice of hardeners to get it to heat up and cure from a liquid to a solid. Fast, medium, slow, ultra slow...the hotter your air temps are the slower we want it to cure.
To the resin/hardener we can decide if we need more of a harder, stronger structural adhesive or a softer fairing compound.
Where folks run into trouble is using epoxy or other adhesives on wood, especially raw wood like a split rudder. The wood grain needs to be sealed to the point where it stops soaking in adhesives. Straight epoxy is a good way, several coats until it is soaked in. Then do the final fastening with a thickened epoxy to fill in all of the tiny nooks and crannies in the joint. Even with THIXO thickened epoxy adhesive we know it will soak in a bit, sucking the adhesive into the grain and the joint. So we leave a little extra during application with that in mind.
Soaking in would NOT be a factor when sealing up a fiberglass joint, but straight epoxy running out of the joint could be, so that's why we use thickened epoxy. THIXO is the right consistency for that repair.
Mama H Chicago
Mother of sailboats
May I use this (with credit of course) to make a T-Shirt??
Straight is resin and hardener, no other additives. It is very runny.
Mama H Chicago
Mother of sailboats
Fussy fussy fussy. I know you know darn well he meant epoxy and hardener ;-). And alas I seem to be unable to apply emojis, so take this as verbal confirmation that I’m poking at you in a good-natured fashion."Straight" epoxy?
No catalyst/hardener?
Epoxy straight-up?
Mama H Chicago
Mother of sailboats
Just wait until I model it here! She’s a beaut!
L&VW
Well-Known Member
I had to ask, because it takes only a drop of hardener to turn the liquid epoxy into a solid. It does take time, but I'm in no rush.
A friend has just reminded me to remove "blush" before proceeding. He maintains "blush" is water-soluble, but I think i'll use denatured alcohol--since there's some handy.
Tops
Mildly Thixotropic
My understanding of polyester and vinylester resins is they are pre-promoted (slowly curing in the jar) and are then accelerated or 'catalyzied' from 1 to 2% with MEKP for use, and this amount plus the ambient temp affects the working time (more MEKP and/or warmer temps makes it go faster).
Epoxy resins are mixed to a certain ratio of resin to hardener expressed as 1:1, 2:1, 3:1, 4:1, and 5:1 which is the part A resin to the part B hardener in units volume. Some systems have a different ratio based on the type or speed of the hardener used and the ratios change slightly when measuring by weight instead of volume. Temps also affect epoxy working and curing time and some slower system stop curing at 60 F.
It was explained to me that epoxy resin is stoichiometric (second vocabulary word of the week, thixotropic was the first...) and mixing epoxy components out of ratio will result in either unused part A or part B components softening the final product. I have only had one bad lamination to date and that was from not having enough hardener in a 2:1 mix and I had to remove the cloth and resin and scrape off the non-curing resin and start over. It was a small project but a good object lesson.
My first quart of epoxy was branded for boat building and was 4:1. My next 10 gallons were various brands but all 2:1 low blush clear formulas. I am finishing a particularly slow 2:1 batch and just got some fast 4:1 which I will have to remember to mix correctly and remove the amine blush between applications. I thought it was water-soluble too, I will have to confirm.
If I have questions about a specific resin, I go to the supplier or the actual manufacturer. For general tips and specific instructions for projects and fillers/additives, the West System websites are really good.
Epoxy resins are mixed to a certain ratio of resin to hardener expressed as 1:1, 2:1, 3:1, 4:1, and 5:1 which is the part A resin to the part B hardener in units volume. Some systems have a different ratio based on the type or speed of the hardener used and the ratios change slightly when measuring by weight instead of volume. Temps also affect epoxy working and curing time and some slower system stop curing at 60 F.
It was explained to me that epoxy resin is stoichiometric (second vocabulary word of the week, thixotropic was the first...) and mixing epoxy components out of ratio will result in either unused part A or part B components softening the final product. I have only had one bad lamination to date and that was from not having enough hardener in a 2:1 mix and I had to remove the cloth and resin and scrape off the non-curing resin and start over. It was a small project but a good object lesson.
My first quart of epoxy was branded for boat building and was 4:1. My next 10 gallons were various brands but all 2:1 low blush clear formulas. I am finishing a particularly slow 2:1 batch and just got some fast 4:1 which I will have to remember to mix correctly and remove the amine blush between applications. I thought it was water-soluble too, I will have to confirm.
If I have questions about a specific resin, I go to the supplier or the actual manufacturer. For general tips and specific instructions for projects and fillers/additives, the West System websites are really good.
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Tops
Mildly Thixotropic
PS:
"Amine blush, a byproduct of the epoxy curing process, may form under certain conditions. This waxy film is water-soluble, but many organic solvents are ineffective for removing it. That is why we suggest washing an epoxy surface with water (water clean enough to drink) using a Scotch-Brite™ pad (or wet sanding with waterproof wet/dry sandpaper) and drying it with paper towels before continuing with another operation. Soapy water, or water with ammonia or bleach, is not necessary and may leave its own residue, which is another possible surface contaminant."
Surface Preparation | WEST SYSTEM Epoxy
"Amine blush, a byproduct of the epoxy curing process, may form under certain conditions. This waxy film is water-soluble, but many organic solvents are ineffective for removing it. That is why we suggest washing an epoxy surface with water (water clean enough to drink) using a Scotch-Brite™ pad (or wet sanding with waterproof wet/dry sandpaper) and drying it with paper towels before continuing with another operation. Soapy water, or water with ammonia or bleach, is not necessary and may leave its own residue, which is another possible surface contaminant."
Surface Preparation | WEST SYSTEM Epoxy
Good infor Tops,
Some folks are good at measuring and mixing, we are not. We prefer the pumps, they do the measuring. Read the instructions with the pumps carefully, they are different sizes for 5:1, 2:1, etc... and have different length stems for the different size cans.
We like to use "Special Clear Hardener" as it doesn't blush and subsequent coats can be applied without sanding, as long as the first coats have not cured. We can even "hot coat," which means we put on one coat and proceed directly to the second coat. Special Clear also does not turn amber.
My marine carpenter friend recommended the Special Clear hardener, he uses it on high end yacht interior finishes. He normally does not varnish on top of it because interior wood does not need the protection from UV like exterior coatings do. We didn't varnish ZIP either, because he is spoiled and sleeps indoors.
Any epoxy that I know of, or poly for that matter, needs some kind of protective coating such as varnish or paint, to protect it from the UV.
Some folks are good at measuring and mixing, we are not. We prefer the pumps, they do the measuring. Read the instructions with the pumps carefully, they are different sizes for 5:1, 2:1, etc... and have different length stems for the different size cans.
We like to use "Special Clear Hardener" as it doesn't blush and subsequent coats can be applied without sanding, as long as the first coats have not cured. We can even "hot coat," which means we put on one coat and proceed directly to the second coat. Special Clear also does not turn amber.
My marine carpenter friend recommended the Special Clear hardener, he uses it on high end yacht interior finishes. He normally does not varnish on top of it because interior wood does not need the protection from UV like exterior coatings do. We didn't varnish ZIP either, because he is spoiled and sleeps indoors.
Any epoxy that I know of, or poly for that matter, needs some kind of protective coating such as varnish or paint, to protect it from the UV.
