Published February 6, 2020
You are an engineer. They are chemists.
You will get the best results by talking to the UV Chemist using Engineering vocabulary (application and product performance). Unless you are the rare individual who is capable of making the UV formulation yourself, please do not talk chemistry with the UV Chemist.
Talking chemistry with the chemist is a distraction. Stick with Engineering performance. Why? UV Chemistry is a specialty. UV Formulation Chemistry is not taught in colleges or Universities. So, unless a chemist has actually formulated and sold UV formulations, bringing in your in-house chemist to help will only slow the initial development process down. This is because UV formulation strategies are counter-intuitive to general polymer chemistry. If you have an in-house chemist, please save them for testing and validations—they will spot chemical things engineers might miss or misinterpret—honestly, that is where you will get the most value from your in-house chemist.
What does the UV Chemist need to know?
The UV Chemist needs to know everything about how the chemistry will be applied, taking into consideration the expectations for how fast it will be cured, the price, and its performance. If this is a new process and if no capital equipment has been purchased, then start with your performance requirements. Determining the performance requirements will then dictate what will turn out to be the best application and cure choices.
Performance requirements should consider both the starting needs and the life of your product. Here are a few examples of the life of the product:
- If your product is a toaster, the expected life is 10+ years in a kitchen (contact with heat, oil, grease, butter, jam, and household cleaners is expected).
- If your product needs a manufacturing aid (like a protect UV patch), then it is applied on one side of the manufacturing plant and removed on the other side—then the life is minutes to days and the patch only has to endure the very predictable environment of the plant.
- On the other hand, if the product goes on to either a vehicle, medical device, military hardware, or circuit boards, then there are a whole host of industry-specific tests that you and the chemist must consider. While you are aware of these industry standards, your UV chemist may not be familiar with your industry and its Standard Test Methods.
The UV chemist must know both the performance needs of your specific product and especially to what environment the product will be exposed to. With this information, the chemist will develop a UV formulation that does not limit your product’s life and may even extend its life and utility.
Application: After the UV chemist has a solution to meet the performance requirements, it is important to consider the application method. Other than printing press applications, it is best not to predetermine the application method. If switching from a non-UV to a UV application, it is best to choose a process after selecting the UV chemistry. For example, if the former process was a dip coating and you only need a coating on one side of the product, you will spend a lot of money extra money on UV lamps or mechanisms and tracks that flip your product–all in an attempt to cure unnecessary chemistry where light has a difficult time reaching. If you truly need 3-D coverage, then dip coating may be the best solution—but the UV chemist will have to formulate the coating so 1) your product can be dipped without creating air bubbles, 2) the liquid will flow and wet to form a uniformly thick coating, and 3) the bath will not slowly polymerize beneath standard lighting.
With any application, the UV chemist will have to adjust the viscosity and thixotropy of the UV coating to be compatible with the application method. For example, the viscosity of a spray coating can never be too thin. The UV chemist may have to adjust the appearance of the product. Nobody is fussy about appearance inside a sealed container, but an exterior surface can never be too alluring.
Curing: The UV chemist needs to know your production speed or throughput targets. They will adjust the formula to improve its cure speed with the right combination of photoinitiators and coinitiators without sacrificing the performance of your product. Cure speed, of course, is also controlled by the lamp system as well as the chemistry. Miltec UV manufactures the fastest curing lamps in the UV industry. So, after defining the chemistry, the best thing to do is optimize the chemistry with the lamps. The best place to that is in the Miltec Customer Application Laboratory.
Miltec UV has an extensive customer application laboratory that is capable of multiple coating methods (roll coating, spray, flexographic, gravure, slot-die as well as numerous table-top application methods). Miltec’s application laboratory has a complete array of curing lamps, conveyors and roll to roll processes that allows you and your chemical supplier to visit and validate your process and product performance so you are confident that you are investing in the right chemistry and uv equipment.
Written by: John Arnold