There’s a difference between UL certification and UL compliance. Learn what it is, why it matters, and what it has to do with rubber products.  

Underwriters Laboratories (UL) develops standards for a variety of industries, including materials and electronics. For rubber products, UL standards cover characteristics such as flammability, tensile strength, elongation, heat resistance, and environmental safety. If your project references UL standards, do you need rubber that is UL certified? Do you need UL compliant rubber instead?

Key Differences: UL Certification vs. UL Compliance

The table below summarizes the main differences.

 

UL Certification

UL Compliance

Testing and Verification

UL or a UL-approved organization tests the product according to UL standards.

The manufacturer of the product (and not UL) tests it. There’s no third-part verification of the results.

UL Marking

UL certified products bear an official UL mark. They also have a Yellow Card.

UL compliant products do not bear a UL mark and do not have a Yellow Card.

Ongoing Monitoring

Certified products are subject to ongoing audits. If the product changes, it must be re-tested.

Compliant products are not subject to audits. If the product changes, it might not be retested.

Understanding UL Rubber

This article from Elasto Proxy is the first in a series about UL rubber. It explains the difference between UL certification and UL compliance with a focus on products like bulb trim, edge trim, and extruded profiles. Elasto Proxy can supply the materials you need, and we also offer finished products.  

UL certification and UL compliance aren’t the same, but there’s also a difference between a rubber product that’s UL certified or UL compliant and an assembly, such as an electrical or electronic enclosure, that is UL certified or UL compliant.

Keep reading to learn more and contact Elasto Proxy for UL rubber.

ul 94 hb epdm sponge
EC-28-101-EM is a standard profile from Elasto Proxy that's made of UL 94 HB EPDM sponge rubber.

What is UL Certification?

UL certification is designated by an official mark that’s issued by Underwriters Laboratories after a product has undergone testing to confirm its adherence to a specific UL standard. Underwriters Laboratories performs this testing, but other organizations can also perform testing at their own facilities under UL’s Data Acceptance Program.

Application and Documentation

The first step in the UL certification process is the submission of an application with detailed product information, including material specifications and intended use. Typically, the manufacturer of the rubber product submits the application. UL, or an organization in UL’s Data Acceptance Program, then conducts a series of tests to evaluate the product against a UL standard.    

UL Listed vs. UL Recognized

Products can be UL listed or UL recognized.

  • UL Listed applies to whole products (such as enclosures) that are meant to be used on their own.
  • UL Recognized is for components (such as rubber) that are a meant to be incorporated into this larger whole.

This key distinction explains why enclosures are UL Listed and the rubber that’s used with them is UL Recognized instead.  

UL Marks

If a product passes all tests, it earns a UL mark. There are different marks available, and some only apply to North America while others apply to both North America and Europe. There are also different marks for UL Listed products and UL Recognized products.

The company that submitted the application (typically the manufacturer) also receives certification documents in print and digital formats. The most notable of these documents is a UL Yellow Card.

UL Yellow Cards

When polymeric materials (such as rubber) receive a UL Recognized Component Mark, they automatically receive a Yellow Card. They physical version is yellow in color, but term “Yellow Card” is also used with the PDF version. 

Some UL certified materials appear in the UL Prospector® database. As an engineer, you can use this online resource to find materials and specific information about them.

Audits

UL certification isn’t an endpoint. That’s because UL also conducts periodic surveillance audits and testing to ensure continued compliance with its standards. The manufacturer who submitted the original application pays for these audits, which are typically performed twice a year.

Modifications

If a certified product undergoes modifications, these changes must be approved by UL and the product must be re-evaluated. This is designed to prevent manufacturers from making misleading claims about safety and performance.

It’s also why the UL mark is highly trusted by engineers and end-users.

ul yellow card
Elasto Proxy has a UL Yellow Card for EP-60020-FR. Note the UL Recognized Mark. Click the image above for a PDF download.

What is UL Compliance?

UL compliance does not involve testing or verification by UL or an organization that belongs to the UL Data Acceptance Program. Instead, UL compliance relies upon the manufacturer’s assurance that the product is designed and manufactured to meet UL standards.

Accountability and Verification

Although UL compliance offers some assurance about safety and performance, it lacks the accountability and verification of UL certification. Products that are UL compliant do not have a UL mark, and UL maintains standards of business conduct to discourage counterfeiting.

Risk Recognition

For applications where rubber products are exposed to severe physical stress, flammable environments, or chemical exposure, it can be risky to depend upon UL compliance alone. There are two main scenarios to consider.

  • Sometimes, the manufacturer of the rubber product fails to fully or correctly test a product to UL standards. 
  • There are also instances where a manufacturer replaces an ingredient in a rubber compound with one that is less expensive or easier to source.

Traceability

With a UL certified material, a change in ingredients would invalidate the certification. For industries where material traceability is especially important, such as aerospace, the risk of quality control issues like this can introduce business and technical risks.    

UL listed enclosure
This electrical enclosure is UL listed. Note the black rubber gasket along the edges.

Rubber Products, Enclosures, and UL Standards

Electrical and electronic enclosures use rubber products like bulb trim, edge trim, or extruded profiles for sealing and insulation. These rubber products can be UL certified or UL compliant, but that doesn’t determine the UL status of the enclosure.

In other words, using a UL compliant rubber doesn’t make it a UL compliant enclosure. Similarly, using a UL certified material doesn’t make it a UL certified enclosure.

This is critical for engineers to understand when sourcing rubber products.

UL certified materials are more expensive, so determine whether you really need them for enclosure-level testing and certification. Conversely, your customer may require UL certified materials right down to the component-level. Either way, it’s worth having a discussion with your supplier and your customer.

It’s also worth considering that there’s isn’t just one UL standard, and that a single standard can contain different certifications. For example, the UL 94 V0 standard contains UL 94 V0, UL 94 V1, and UL 94 HB. There are also UL 50 and UL 50E standards that are similar but not the same.

The other articles in this series will help you select the UL rubber that you really need. In the meantime, contact Elasto Proxy for sealing and insulation solutions. We can supply the right materials and fabricate finished products that help you save time and money during assembly.

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