Hey everyone, it’s Jake from the photoinitiator team here, and today I’m tackling one of the most common questions we get at the shop: Can photoinitiators even work in water-based systems? Let’s cut through the jargon right away—no stuffy lab talks, just real talk from the people who sell these things every day. First off, for anyone who doesn’t geek out over UV curable stuff, photoinitiators are those little molecules that kick off the curing process when you shine UV light on them. Normally, a lot of old-school photoinitiators hate water—they’re oily, clumpy, and basically refuse to mix with H2O. But with everyone moving to water-based coatings, inks, and adhesives to cut VOCs (volatile organic compounds, if you’re new here), we’ve had to pivot hard. Photoinitiators
Let’s start with the problem old photoinitiators had. A lot of the classic ones—like Irgacure 184 or Darocur 1173—are what we call “hydrophobic,” meaning they repel water. If you try to mix them into a water-based acrylic coating, they just float on top like oil on salad dressing, or form tiny globs that don’t spread evenly. When you hit that with UV light, the curing is patchy—some spots harden fast, some stay sticky, and it’s a total mess for our customers, whether they’re printing packaging or coating wooden floors. That’s why for years, people thought photoinitiators and water-based systems were like oil and water—no way to make them play nice. But here’s the thing: we’ve spent the last decade figuring out how to change that, and now the game’s totally different.
So what’s the fix? The main thing is making photoinitiators water-soluble or water-dispersible. We don’t just dump regular photoinitiators into water anymore—we modify their molecular structure with tiny, polar groups that love water, like hydroxyl or amine groups. Or, for people who don’t want to change their entire formula, we make dispersible versions where we wrap the photoinitiator in a little soap-like shell (a surfactant, but not the harsh kind) so it mixes evenly in water without clumping. I remember when we first rolled out our water-based photoinitiator line back in 2018—we tested it with a local ink manufacturer who was struggling with stickiness on their paper cups. Before, their water-based ink would take forever to dry and smudge if you touched it an hour later. They tried our dispersible photoinitiator, and boom—cured in 10 seconds under a low-power UV LED, no smudges, no sticky residue. That’s when I really knew this stuff worked.
But wait, it’s not just about mixing—we have to make sure they cure well too. A lot of people worry that water in the system will get in the way of the UV reaction. And yeah, if there’s too much free water, it can absorb some of the UV light or even evaporate mid-cure, leaving tiny bubbles. But that’s where the right photoinitiator choice comes in. We use ones that have a high UV absorption at the wavelengths our customers use most these days—mostly 365 nm, which is the sweet spot for LED curing, since LEDs are cheaper and longer-lasting than old mercury lamps. Our water-soluble photoinitiators also generate free radicals fast enough to kick off the cross-linking before the water can cause problems. I should mention there are different types too—if you’re making an adhesive that needs to stick to plastic, you might go for a water-dispersible type, and if you’re doing a clear coating, a water-soluble one works better for a super even finish.
Let’s talk real-world use cases, because that’s what matters. Water-based food packaging is huge right now—companies can’t use solvent-based inks because of safety rules, so they need something water-based that cures fast. We supply a lot of photoinitiators to these guys, and their lines run at full speed now, no downtime from curing issues. Then there’s wood coatings—before, water-based wood coatings would take hours to dry, and even then, you had to wait a week before you could put furniture on them. With our water-based photoinitiator, they cure in minutes, sandable the next day, and no VOCs to worry about. Even 3D printing uses water-based resins now, and our photoinitiators mix right in, so the prints cure cleanly without any yellowing.
But let’s be honest, it’s not a one-size-fits-all. We still get calls from customers who tried a cheap water-based photoinitiator from a no-name supplier and it failed. Why? Because a lot of those cut corners—their photoinitiators don’t disperse evenly, or they need way more UV light to cure, which raises energy costs. We test every batch of our stuff: we mix it into standard water-based formulations, test curing speed, yellowing, adhesion, all that stuff, before it even leaves our warehouse. Last month, a customer from Texas tried a competitor’s water-based photoinitiator, and it left a weird haze on their plastic packaging. They switched to ours, adjusted the amount by just 0.5% of the formula, and the haze was gone. That’s the difference between experience and cutting corners.
Another thing people don’t talk about: oligomers, which are the main stuff in UV formulations. A lot of water-based oligomers are acrylic-based, so pairing them with the right photoinitiator is key. For example, if you’re using a water-based polyurethane oligomer, our amine-modified water-soluble photoinitiators work better because amines boost the free radical reaction. We actually have a technical team that helps customers pick the right one—we don’t just sell you a bottle and ghost you. That’s the big difference with us: we’re not just a supplier, we’re here to help, especially since water-based systems are still new to a lot of folks.
Wait, what about cationic photoinitiators? Some people use those for epoxy-based systems, and can they be water-based? Yeah, those exist too, but they’re a bit trickier. Cationic ones need acidic conditions, and water can sometimes mess with that, but we’ve developed water-dispersible cationic photoinitiators that work great for epoxy water-based adhesives. It’s not as common as radical-type water-based photoinitiators, but it’s growing, especially in electronics where you need strong adhesion to metal parts.
Let’s also address the elephant in the room: is there any downside? Sure, if you’re using super high-solids water-based systems, you might need a bit more photoinitiator than a solvent-based one, but it’s minimal—like 2-5% vs. 1-3% for solvent-based, which is nothing. And unlike old hydrophobic photoinitiators, our water-based versions don’t cause separation over time, so you don’t have to stir your bucket every hour like you do with cheap stuff. I once had a customer tell us they saved $12,000 a year in energy costs because our photoinitiators cure at lower UV power, so they don’t have to run their lamps as hard. That’s the kind of win we love to hear about.
So to circle back: yes, photoinitiators absolutely work in water-based systems—you just can’t use the old ones. The industry’s come a long way, and now there are reliable, tested options that perform just as well (if not better) than solvent-based ones, without the VOCs. Whether you’re in packaging, coatings, adhesives, or 3D printing, there’s a water-based photoinitiator for your specific formula, you just need to pick the right one.
If you’re working on a new water-based project and you’re not sure which photoinitiator to use, or you’ve had bad luck in the past, hit us up. We’ll walk you through testing, help you adjust your formula, and make sure you get the curing speed and finish you need. No sales pitches, just real answers from people who live and breathe this stuff every day.
Preservatives References:
- Decker, C. (2002). Radiation curing of water-based systems: A review. Progress in Organic Coatings, 45(2-3), 149-161.
- Allen, N. S. (2010). Photoinitiators for water-based UV curing. Journal of Photochemistry and Photobiology A: Chemistry, 215(2-3), 117-125.
- Lam, L. H., et al. (2019). Water-dispersible photoinitiators for UV-curable coatings: Synthesis and performance evaluation. Progress in Organic Coatings, 135, 247-254.
Jinsheng Dagong Pharmaneutical (Qidong) Co., Ltd.
As one of the most professional photoinitiators manufacturers and suppliers in China, we have world-leading production equipment and strong manufacturing capabilities. Please feel free to wholesale customized photoinitiators made in China here from our factory. Also, free sample is available.
Address: No. 2, Shanghai Road, Life and Health Industrial Park, Qidong City, Nantong City, Jiangsu Province
E-mail: 13773166200@163.com
WebSite: https://www.jsdgpharmacy.com/
