Finding the perfect adhesive for your application can be challenging enough, and when we are looking at UL94 rated adhesives, the search can be even more difficult. The UL94 standard in hot melt adhesives provides reduced safety hazards, increased equipment performance, and minimized replacement costs. For more safety tips make sure to check out our 10 Essential Safety Precautions When Working with Hot Melt.
What does UL94 rating mean?
UL is the abbreviation for the Underwriters Laboratories, this is an independent organization in the United States to control and certificate product safety. UL provides safety related certification, validation, inspection and testing services to a range of clients including manufacturers, retailers, policy makers and regulators.
Adhesives can be developed to match a sliding scale of fire resistance - here are the details of the Underwriters Laboratory Testing classifications. As adhesive manufacturers, we are seeing requests mainly for the UL94 V-0 and occasionally for the HB.
UL94 Rating Scale
- HB: Slow burning on a horizontal specimen; burning rate < 76 mm/min for thickness < 3 mm or burning stops before 100 mm.
- V-2: Burning stops within 30 seconds on a vertical specimen; drips of particles allowed as long as they are no inflamed.
- V-1: Burning stops within 30 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.
- V-0: Burning stops within 10 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.
- 5VB: Burning stops within 60 seconds on a vertical specimen; no drips allowed; plaque specimens may develop a hole.
- 5VA: Burning stops within 60 seconds on a vertical specimen; no drips allowed; plaque specimens may not develop a hole.
Adhesive chemists combine a number of additives to make fire retardant adhesives - and sometime even to quench flames (although this feature is harder to achieve nowadays with many goods manufacturers now requesting halogen-free formulations).
It is a careful balance as these additives will cause interference to other adhesive properties such as strength, rheology, cure speed, flexibility, etc.
Is there a difference between fire resistant adhesives and fire-retardant adhesives?
Yes! Both terms have been used in this article but it is probably best to set the story straight.
Fire resistant adhesives - these are often products such as inorganic adhesive cements and sealants. They don't burn and they withstand extreme temperatures. These types of products are often used for applications in blast furnaces, ovens, etc. They don't do anything to stop an assembly burning - but they do a great job of holding all the burning bits together.
Fire retardant adhesives - these help to extinguish the flames and slow the spread of fire.
What are these adhesives used for?
- Electronics - for potting and encapsulating electronics, bonding heat sinks, circuit boards, etc. An electronic short circuit can easily spark a fire but PCBs contain fire retardant compounds - it is often important that adhesives also have these properties.
- Construction - cladding and flooring (particularly in public areas) often has to be non-burning and bonded with a fire-retardant adhesive.
- Public transportation - train carriages, bus interiors, trams, etc. Flame retardant adhesives are used for bonding composite panels, flooring, and other fixtures and fittings. Not only do adhesives help stop the spread of fire, but they provide an aesthetic joint without the need for unsightly (and rattly) mechanical fasteners.
- Aircraft - as mentioned earlier, cabin interior materials are under strict regulations and must be fire retardant and not fill the cabin with black smoke during a fire.
Featured UL94 Hot Melt Adhesives
- The 3M 3748 VO is a unique hot melt adhesive often used in electronic assembly because it provides excellent thermal shock resistance and is non-corrosive to copper. The 3M 3748 VO also provides an excellent bond to polyolefins and meets UL 1410 requirements.
- Infinity Bond A6350 is a high performance product assembly hot melt adhesive with an open time under 10 seconds. Infinity Bond A6350 is unique in that it offers a UL 94V2 listing making it a favorite among product assembly applications. This hot melt has excellent temperature resistance and offers a strong bond to a wide range of substrates.
- This Infinity Bond high performance bulk hot melt is excellent for product assembly applications and carries a UL 94 V2 flame rating. It is also FDA approved for non-direct food contact. This APAO bulk hot melt has a medium to low viscosity and a medium open time of about 60 seconds. It is great for product assembly applications with high tack and overall strength. It offers exceptional thermal stability and has a low tensile strength.
- This polyamide hot melt is a high performance thermoplastic that is formulated to be used for low pressure injection molding. This bulk polyamide hot melt provides a protection from environmental factors and has excellent resistance to liquid - UL 94 VO listed.
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Innovation & Safety with Your Needs in Mind
We are excited to offer our valued customers the best products for every unique application. We work closely with many industries requiring flame retardant adhesives and we understand their unique safety requirements. If you have any questions or would like additional information, reach out to one of our adhesive specialists today!
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