So you think that a UV curable resin might be right for you and your assembly or manufacturing process. You've heard of the reduced production costs and the unparalleled polymerization speeds, but you're still not sure if a UV curable adhesive or sealant will work well for your application.
Even if you already think a UV curing system will work great for your application, you might not know where to go next to receive specific product technical data, material samples, and really begin the testing/ prototyping process.
If you fit any of the above criteria, or you're simply interested to learn more about UV and visible light curing adhesives & sealants, this guide is for you. In this massive post we tackle the following questions & topics:
1) Why Consider A UV Resin? - including an introduction to UV resin technology, as well as outlining some of the benefits and drawbacks of a UV-based manufacturing process.
2) Will A UV Curing Product Work For Your Application? - including typical UV acrylate properties.
3) What Are Some Of The Specialized UV Cure Resin Products? - including dual curing systems and UV cationic epoxies.
4) What Are Some Industries That Use UV Curing Systems? - including industry specific examples.
5) How Can You Find The Best UV Curable Resin For Your Application? - including an opportunity for free one-on-one consulting from Cova Scientific.
1) Why Consider A UV Resin
A Short Introduction To UV Adhesives & Sealants
As you probably already know or can infer, UV (ultraviolet) curable resins are similar in function to traditional adhesive & sealant products. Like an epoxy, silicone, or polyurethane, UV resins are liquid materials that can be cured via a polymerization reaction to either bond, coat, pot, or seal components.
However unlike traditional adhesives, these system are polymerized via radiation, normally within the UV spectrum.
UV curable resin formulations are normally comprised of four fundamental components:
- Oligomers are low-molecular weight polymers that make up the bulk of the resin formulation and determine most of the final polymerized properties. Most oligomers used in UV cure resins are acrylates, and thus generalizations referring to UV curable resins are most likely referring to UV acrylates. For our discussion we will mainly be referring to UV acrylates.
- Monomers are either monofunctional or multifunctional molecules that are utilized to manipulate the viscosity of the uncured product. Monomers generally make up a smaller percentage of the final formulation and have a small influence on the properties of the final polymerized product.
- Additives are normally non-reactive components used to manipulate both the uncured and cured properties of the product. Additive examples include: stabilizers to extend a product's shelf-life, color pigments, defoaming agents, wetting agents, and more.
- Photoinitiators are the basis of all UV cure reactions. When a photoinitiator is exposed to the correct wavelength of radiation it initiates the UV-polymerization reaction. Depending on the photoinitiator chosen a UV curable resin might be sensitive to radiation within the UVC, UVB, UVA or even visible light ranges. Once the photoinitiator has been exposed to the correct radiation wavelength, the free radical polymerization reaction it initiates normally completes in a matter of seconds.
These four components can be varied to formulate a wide variety of UV curable product products. But at the end of the day all UV curable resins will exhibit three main benefits:
- UV resins are one-part systems
- UV resins can cure faster than any alternative
- UV resins can be cured-on-demand
So why consider a UV curable product? Because each of the above benefits translate directly to reduced production costs. Specifically:
- Reduced labor costs
- Reduced equipment costs
- Reduced work-in-progress
- Reduced set up and clean up labor
- Faster production speeds and capacity
- Less required floor space
- Increased yield
To put numbers to these claims Heraeus Noblelight America conducted a series of calculations comparing UV curable products against traditional systems:
- The first example examines the cash flow improvements of an electro-optical manufacturing process. Basically the manufacturer produces 50 assemblies per month each with a value of approximately $50,000. Each subassembly requires about 10-15 different adhesive bonds, and ultimately the entire assembly requires about 100 bonds. While utilizing slow curing RTV silicones and traditional epoxies, one assembly takes approximately 4 months to complete. When the manufacturer instead utilizes a UV curable adhesive, however, the assembly process is reduced from 4 months to 2 hours. The work-in-process product value is therefore reduced from $2,500,000 to $18,750.
- The second example examines the reduced set-up and clean-up labor costs of UV systems. Because UV resins will not cure without exposure to UV light, a graphic arts printing press leaves the resin in the machinery overnight. As a result the set-up/ clean-up costs of the printing press are approximately $500/ day vs. an estimated $1,500/ day if they were to use a solvent or water based material that would require a more extensive clean-up process.
- The last example examines the savings realized due to the reduced floor space requirements. A typical drying oven might require 500 to 1000 square feet whereas a UV curing process would only require about 50 to 100 square feet. At $0.50/ft2/month that is $250-500/ month compared to $25-50/ month for the UV process.
The results from the above examples can be compared in the table below.
Created with Compare Ninja
Although these are very specific cases, the point is clear: massive savings can be realized when a UV curable material is used instead of a more traditional approach.
Of course, however, UV curable resins have their limitations and drawbacks.
UV curable materials are only suitable in applications where UV radiation can reach the photoinitiator species. This immediately eliminates any application that involves bonding opaque substrates. It also prevents polymer variations that require high concentrations of fillers such as thermally and electrically conductive polymers.
UV curable polymers will also never match...
- The extreme chemical resistance of epoxies
- The heat resistance of silicones
- And durability of polyurethanes
The following table summarizes some of the high-level benefits and drawbacks of UV curable adhesives & sealants vs. more traditional alternatives:
Created with Compare Ninja
At the end of the day UV products are great for many applications and there are probably countless manufacturing processes today that would realize substantial cost savings if they transitioned to a UV assembly process. However, there are certain applications that simply can not be solved with a UV adhesive.
The next section spells out the typical properties of UV curable adhesives & sealants so you can begin to understand if a UV resin is right for your application.
2) Will A UV Curing Product Work For Your Application?
Typical UV Adhesive & Sealant Properties
Let's jump right in by examining the table below that outlines some of the typical values of a UV curable adhesive or sealant. As you read through the following table, try to keep in mind the properties that are important to your application and take note if it seems that a UV product will meet your application specifications.
Created with Compare Ninja
Even If it appears that a UV adhesive won't work for your application, don't fear!
Although the values listed in the table above are the typical properties of a UV cure resin, there are exceptions to the rule. The next section works to explain some specialized UV resin variations that may be perfect for more complex assembly procedures.
3) What Are Some Of The Specialized UV Cure Resin Products?
Specialized UV Curing Resins
As we explained in section 1, most UV curable resins are based on acrylate chemistry. This includes:
- Epoxy Acrylates
- Urethane Acrylates
- Polyester Acrylates
- Polyether Acrylates
- Acrylic Acrylates
- And more...
However, there are other types of UV curable resins that offer unique properties and capabilities.
- Dual Curable Resins are two-part systems that once mixed will proceed to polymerize at room temperature (or with heat) or will set immediately with UV exposure. These systems are also called acrylate epoxy blends or UV gel epoxies because the resin is comprised of a traditional UV adhesive mixed into the resin side of a two-part epoxy. These systems are essentially a set-on-demand version of a traditional epoxy. Although the system will not reach 100% polymerization with exposure to UV light, the resin will advance enough to "gel" which will eliminate any flow or further movement. These systems can also cure in dark sections, unlike a traditional UV resin.
- Anaerobic UV Resins are one-part systems that will either cure with exposure to UV radiation or in the absence of oxygen. Basically these systems contain components that will readily react, however, airborne oxygen establishes a chemical atmosphere that prevents this reaction from occurring. As soon as oxygen is removed from direct contact with these components the reaction proceeds. These systems are particularly useful for curing in dark sections, especially when the substrates are metal (metal catalyzes the anaerobic reaction).
- Cationic UV Curable Epoxies are one-part systems that generally operate similar to traditional UV acrylates, however, their unique chemistry offers some interesting advantages. Some advantages include increased temperature and chemical resistance, but the most notable advantage is the ability to delay cure. Although cationic epoxies are light-sensitive just like UV acrylates, they can be formulated to delay the polymerization reaction for a short time period. Effectively, this means that cationic resins can be used to bond opaque substrates because UV light is only needed to initiate the reaction, not complete it.
Beyond these differing chemistry types, UV acrylates can also be modified beyond the properties described in section 2 . Adhesive formulators and raw material manufacturers are constantly pushing the limits of UV curing products. If you're potentially interested in pursuing a UV adhesive or sealant with properties outside the normal limits, see section 5 of this guide.
The next section works to describe some common uses of UV resins so you can understand where UV products have a proven track record.
4) What Are Some Industries That Use UV Curing Systems?
UV Curable Material Uses
UV curing systems are utilized across a wide range of industries and applications. The following are just a few of the many examples:
- 3D printing - Some 3D printers, such as those designed by Formlabs and Carbon3D use stereolithography and UV curable resins to produce three dimensional objects. Basically, UV lasers are used to draw solid shapes out of a bath of UV resin.
- Automotive - UV adhesives & sealants are commonly used to coat automotive components including headlamp lenses - providing scratch and chip resistance - as well as to several under-hood and interior components.
- Electronics - Examples of electronic products that utilize UV curing systems include die attachments, sealing and gasketing products (form-in-place gaskets), flex circuit reinforcement, and magnet bonding. UV products are also commonly used to coat PCBs, wires, computer chips, cellphones, and smart cards.
- Medical - Various UV reactive resins have been shown to meet ISO 10993 and USP Class VI medical standards for use in medical devices. UV resins are typically used to bond components in syringes, guide wire tips, medical tapes, hearing aids, and other types of implantable and non-implantable devices. UV adhesives are particularly useful due to their ability to bond the types of plastics commonly used in medical devices.
- Optics - Optical applications include display bonding, LED/ LCD encapsulation, and fiber-optic coating. UV adhesives that have been formulated for optical applications tend to display excellent light transmission properties and impart very low level of stress on bonded components.
The uses of UV curing systems extend to many more industries and application than the simple list above. Additional examples include aerospace, appliance, industrial, metal finishing, orthopedic, packaging, power supply, and speakers.
The next section explains how to find a UV resin for your specific application.
5) How Can You Find The Best UV Curable Resin For Your Application
How To Best Proceed
By this point you've learned quite a bit about UV resins and you might even have a pretty good idea as to what properties will work well for your application. Or you might still have specific questions that will help you further determine the viability of a UV based manufacturing process.
Specifically you might be wondering:
- How do I know for sure if a UV resin will work well for my manufacturing process?
- Where do I find and how do I select the right product for my application?
- How do I estimate my expected material usage, and equipment requirements?
- How do I estimate the costs associated with UV resins and UV curing equipment?
- How do I really know if a UV curing process is the best option?
Unfortunately, the answer to every question above is:
Every application is so different, and even between similar applications there can be any number of differing variables.
For this reason, the best way we would suggest that you begin your research process is by starting a conversation with an adhesive & sealant expert. A seasoned adhesive chemist will be able help you narrow down your product selection process according to both your assembly and monetary requirements.
One big mistake we commonly see is engineers attempting to select a product on their own. Normally this involves searching through dozens of Technical Data Sheets (TDSs) online until a product that seem to meet the technical requirements is discovered.
At this point an engineer will reach out to the resin supplier and request a sample/ price quote. In response the UV resin supplier will most likely say, "tell me a little about your application." Chances are, after the engineer explains his assembly requirements and monetary limits, they'll suggest a completely different product.
The point is:
Don't waste your time searching through product data online, reach out to an expert from the start!
So how do you find an adhesive & sealant expert? Well, you're reading an article by one right now!
At Cova Scientific not only do we produce educational content to help you research specialty adhesives & sealants on the web, we're also happy to talk to you about your application and help your find the best product/ supplier for your specific requirements.
- Tell us a bit about your application so we can begin understanding your specific requirements and potential adhesive & sealant needs.
- We'll reach out to you within 24 hours with a set of more specific questions so we can narrow in on the best product or product category to meet your needs.
- Once we understand you specific goals and challenges we'll put you in direct contact with the most relevant suppliers so they can provide product samples and pricing quotes.
Click the link below to find out more about the Cova Process!