Sunday, June 10, 2007
Suntanning blotches... in an Amsterdam summer day??
I have received my UV fluorescent, a Cleo Compact of 15W. It cost me 6€ and is very easy to get in any illumination ware store. The tube allows for a fairly compact mount, as it is only 30cm long (about a foot). They didn't have the mount there for it so i bought the parts and made it myself out of this simple diagram i got from the Wikipedia.
I used a reflectant non conductive mylar plastic strip from a candy bar (Twix, to name it), to use as a reflector. The end result looks like this (left).The bad news is that the spectrum of this lamp is adjusted to mimic the natural solar spectrum of an Amsterdam July day at noon! I'm not kidding!! I was hoping for an ozone-depleted, antarctic, January at noon spectrum! :)
The result is that after my first test-run i had not enough UV-power at the desired wavelengths to get a quick polymerization. It took 2-3 hours to get the resin to set and probably another hour or two to get it to harden... far to long! I will be ordering a black light tube (Philips TLK 40W/10R or F40BL 40W) which have an emission peak at 365nm, exactly what i need for Mechlers Ketone. They deliver 7.4 and 9W of UV radiation each, which is a lot better than the Cleo tube and the price is very similar, although the tubes are twice as big. If the results keep being to poor, I will be aiming for the 100W bulb range, which will certainly do the job, but at a higher price. I will also buy a germicidal UV fluo (philips TUV25T8), which works at the wavelength of Benzophenone.
One last thing slowing down the setting is an effect called Oxygen scavenging. It results through the effect of air Oxygen on the surface, which destroys the radicals formed by the UV radiation inside the resin mix and that are responsible for its polymerization. This causes the surface of the resin deposit to remain liquid while the interior continues curing. There are two ways to solve this problem:
1) Augmenting the photoinitiator of the mix (from 2-3 weight % to 6-10 w%)
this solution is simple but on the expensive side.
2) Adding 2-3 w% of an Amine such as N-Methyldiethanolamine, wich costs around 25€ per kilogram and is a cheap additive and which will react with the solved oxygen in the resin, preventing the radicals scavenging.
One thing i thought of too is to let some resin blotches lie in the Sun (Barcelona Sun, not Amsterdam!). And it did work! I got some slow polymerization on, and i suppose that in 12h exposure the resin would set as well.
One last important effect and that will have great implications for the deposition process. The resin remains tacky and sticky right until the end of the curing process. By timing the UV-exposure and the Amine content correctly, we could achieve seamless interlayer adhesion, almost as if the object had been cast in one piece!
Labels: Lamps, photoinitiator, resins, UV
Tuesday, June 05, 2007
Mixmaster is ready to get mixin'
Today I finally got the delivery from Acros.
They deliver at home and have really good prices, but the initial registration process took a month for me. They seem to act through a local branch, but their products are delivered from central warehouses and deliver for free if you order over 100$/€.
These people are reliable but if you have a local chemical products shop, use them, as they will speed up the whole process. That's worthwhile even at a little more expensive prices.
So what did I get?
1) 1kg of Methyl-methacrylate (the stuff Plexiglas is made of). It's a clear sweet smelling, flammable liquid, with quite a low viscosity (something like water)
I'll use this as the first of my three resin bases. 1kg cost me around 18€
2) Benzophenone. My first photoinitiator. It's a solid, pretty harmless. It will work with pretty energetic UV, the kind used to kill germs. 500gr cost me 25€ (between 1 and 3% in weight will be used in the final mixed resins)
3) Mechelers Ketone. The second photoinitiator. It's a gray-greenish solid, not to be inhaled or spread over your sandwich. This one works with the UV used for tanning. 100gr cost me 19€ (same proportion as for Benzophenone needed).
I have allready ordered the UV tube wich should arrive this week too, it cost me 6€. I'll write more closely on that when it gets here.
4) I bought 1kg of regular Polyester resin (comes mixed with styrene as a solvent monomer). It's the one you can get at paint shops for car repair, fiberglass molding and resin casting. It cost me 20€, but you could probably get it a lot cheaper than that. I will look for a shop that has better prices. This will be the base for my second types of resins.
I will also try to find a standard epoxy resin that will be the third of my initial batches for tests.
I have some good ideas about the tests i will do. They involve cure depth, cure speed, cure and setting times, filler properties, viscosity check (tricky one).
If you have other ideas on trials i could make, please drop me a line.
They deliver at home and have really good prices, but the initial registration process took a month for me. They seem to act through a local branch, but their products are delivered from central warehouses and deliver for free if you order over 100$/€.
These people are reliable but if you have a local chemical products shop, use them, as they will speed up the whole process. That's worthwhile even at a little more expensive prices.
So what did I get?
1) 1kg of Methyl-methacrylate (the stuff Plexiglas is made of). It's a clear sweet smelling, flammable liquid, with quite a low viscosity (something like water)
I'll use this as the first of my three resin bases. 1kg cost me around 18€
2) Benzophenone. My first photoinitiator. It's a solid, pretty harmless. It will work with pretty energetic UV, the kind used to kill germs. 500gr cost me 25€ (between 1 and 3% in weight will be used in the final mixed resins)
3) Mechelers Ketone. The second photoinitiator. It's a gray-greenish solid, not to be inhaled or spread over your sandwich. This one works with the UV used for tanning. 100gr cost me 19€ (same proportion as for Benzophenone needed).
I have allready ordered the UV tube wich should arrive this week too, it cost me 6€. I'll write more closely on that when it gets here.
4) I bought 1kg of regular Polyester resin (comes mixed with styrene as a solvent monomer). It's the one you can get at paint shops for car repair, fiberglass molding and resin casting. It cost me 20€, but you could probably get it a lot cheaper than that. I will look for a shop that has better prices. This will be the base for my second types of resins.
I will also try to find a standard epoxy resin that will be the third of my initial batches for tests.
I have some good ideas about the tests i will do. They involve cure depth, cure speed, cure and setting times, filler properties, viscosity check (tricky one).
If you have other ideas on trials i could make, please drop me a line.
Labels: photoinitiator, Printing materials, UV
