If you are designing with plastic and have not considered flame ratings, you are gambling with more than compliance. UL 94 is not just a label – it is a gatekeeper. The difference between a V‑0 and a V‑2 rating can mean the difference between approved production and a costly redesign.
For example, if you have ever watched a perfectly engineered part fail certification because your wall thickness dropped below the test threshold, you are not alone.
Applications for Flame‑Retardant Plastics
UL 94 rated materials are commonly used in:
- Automotive under‑hood components (PA, PPS)
- Cooling fans and brackets (PBT, LCP)
- Electrical enclosures and switch housings (PC, ABS/PC blends)
- Industrial cable guides and electronic components (PP, PEEK)
- Medical device housings (PPSU)
- Telecom hardware and connector housings (ABS, PC/ABS)
These parts often face elevated temperatures, mechanical load, and proximity to electrical current, making flame retardance critical to safety and compliance.
For more information on industry‑specific material requirements, see our [Internal Link: Industries Overview → /industries/] (yellow – optional).
What is UL 94?
UL 94 is a plastics flammability standard developed by Underwriters Laboratories. It evaluates how plastics react to an open flame, measuring ignition time, self‑extinguishing behaviour, and whether flaming drips ignite a secondary cotton indicator. UL 94 is compatible with other international standards, giving it global relevance for flame safety testing.
Test setups vary. The HB rating involves horizontal burn evaluation. Other rating classifications – such as the V and 5V series – use vertical bars or plaques.
Within the V series, the difference between V‑0 and V‑1 is that a V‑0 material meets a higher level of criteria under the same test conditions. Test conditions are more stringent when moving from the V to 5V ratings group, with 5V testing requiring a higher level of resistance to flammability.
UL 94 Ratings at a Glance
| Rating | Primary Criteria |
|---|---|
| HB | Slow burning on a horizontal part |
| V‑2 | Burning stops within 30 seconds on a vertical part; allows flaming drops that ignite cotton |
| V‑1 | Burning stops within 30 seconds on a vertical part; allows drops of plastic that are not in flame |
| V‑0 | Burning stops within 10 seconds on a vertical part; allows drops of plastic that are not in flame |
| 5VB | Burning stops within 60 seconds on a vertical part; no flaming drops; test specimens may have burn‑through (hole allowed) |
| 5VA | Same as 5VB, but no burn‑through allowed on the plaque – highest UL 94 classification. Burning stops within 60 seconds; no flaming drops; no hole permitted |
Classifying materials as 5VA or 5VB involves a 125 mm vertical burn test using a Bunsen burner flame. Bars and plaques have specific size and thickness requirements, and the flame is applied in five‑second intervals with five seconds flame‑free between each application. For the V series, a 20 mm flame is applied twice for ten seconds each time.
For detailed material data sheets, visit our [Internal Link: Materials Resource Center → /materials/] (green – strong).
Flame‑Retardant vs. Flame‑Resistant: What’s the Difference?
- Flame‑retardant materials are engineered to slow ignition and suppress flame spread. They may catch fire but self‑extinguish once the ignition source is removed. UL 94 classifications fall into this category.
- Flame‑resistant materials resist ignition entirely and are often used in textiles or personal protective equipment. These are tested under different standards, such as ASTM D6413 or ISO 15025.
Understanding this distinction helps engineers select materials based on both functional performance and regulatory fit.
Why Thickness and Formulation Matter
UL 94 ratings are thickness dependent. A resin that passes at 1.5 mm may fail at 0.74 mm. Some materials perform consistently across a wide range of wall thicknesses, but this is not guaranteed.
Formulation also plays a critical role. Most flame‑retardant grades rely on specific additives to meet performance targets. Even small changes (such as switching colorants) can void certification unless the new blend is tested and certified independently.
When in doubt, ask your material supplier for a UL Yellow Card – a certification that the material has undergone safety and performance testing. It should cover the full formulation and your required thickness range.
For assistance with material selection, [Internal Link: contact our application engineers → /contact-us/] (green – strong).
Flame‑Retardant Materials Available at Konlida
We offer a variety of UL 94‑rated materials for injection moulding [Internal Link: /services/injection-molding/] (green) and 3D printing [Internal Link: /services/3d-printing/] (green). Customer‑supplied resins can also be evaluated on request. Be aware that the same material can have different ratings based on a variety of factors – you cannot simply assume a material is V‑0 rated.
In addition to dozens of UL 94‑rated materials for injection moulding, we have added a flame‑retardant option for 3D printing:
Arkema FR512 – a flame‑retardant photopolymer used in our high‑performance printing process, achieving UL 94 V‑0 at 0.79 mm. It is ideal for intricate parts requiring detailed resolution and certified fire retardance.
PFAS in Flame‑Retardant Materials
Per‑ and poly‑fluoroalkyl substances (PFAS) have long been used in flame‑retardant additives for their exceptional thermal and chemical resistance. However, PFAS are now under increasing regulatory pressure due to their persistence in the environment and links to potential health risks.
While some flame‑retardant materials still contain PFAS, many manufacturers are moving away from them.
We closely monitor PFAS regulations. While PFAS content is not currently listed in our material data, we encourage customers with regulatory or environmental concerns to reach out. We can help you explore alternatives or confirm specific resin compositions when needed.
For sustainability inquiries, see our [Internal Link: Environmental Policy → /sustainability/] (yellow – optional).
Environmental Considerations
Flame retardants improve fire safety but can complicate product end‑of‑life handling. Halogenated additives are difficult to separate during recycling and may release toxic compounds if incinerated.
Because of this, there is growing interest in non‑halogenated flame retardants that offer similar performance with a reduced environmental footprint. Material selection should always account for both safety and sustainability.
Why Flame Ratings Matter in Product Development
UL 94 ratings are not just technical details. They often determine whether a part can be used in regulated industries such as aerospace, medical, automotive, and consumer electronics.
Choosing a certified flame‑rated material early helps avoid compliance issues, costly redesigns, and late‑stage certification failures.
One More Thing Before You Submit Your Design
UL certification is formulation specific. A resin may carry a Yellow Card, but custom blends, colorants, additives, and other alterations to the base material may affect its rating.
If you are working in industries where multiple property standards apply – such as smoke, toxicity, or thermal ageing – be sure to validate the full material profile before production.
For more information on injection moulding material properties, read our [Internal Link: Injection Molding Material Selection Guide → /resources/injection-molding-material-selection/] (yellow – optional).
UL 94 might seem like regulatory fine print, but it plays a defining role in what gets built, what gets approved, and what gets flagged for redesign. Our applications engineers are available to help you make the right decision for your application, budget, and schedule.
Frequently Asked Questions
What is UL 94 and why does it matter?
UL 94 is a plastics flammability standard that evaluates how materials react to an open flame – ignition, self‑extinguishing behaviour, and whether flaming drips ignite a cotton indicator. It is widely recognised and often required in regulated industries.
What do the main UL 94 ratings (HB, V, and 5V) mean?
- HB: Slow burning on a horizontal specimen.
- V‑2: Vertical specimen stops burning within 30 s; flaming drips that can ignite cotton are allowed.
- V‑1: Vertical specimen stops burning within 30 s; no flaming drips that ignite cotton.
- V‑0: Vertical specimen stops burning within 10 s; no flaming drips that ignite cotton.
- 5VB/5VA: More stringent vertical tests with a larger flame; no flaming drips. 5VB permits burn‑through (holes), while 5VA – the highest UL 94 rating – does not.
How do part thickness and formulation affect a UL 94 rating?
Ratings are thickness‑dependent and formulation‑specific. A resin that meets V‑0 at 1.5 mm may fail at 0.74 mm. Even small formulation changes (e.g. a new colorant) can invalidate a prior rating. Always confirm with the material’s UL Yellow Card.
What is the difference between flame‑retardant and flame‑resistant materials?
- Flame‑retardant: Slows ignition and self‑extinguishes after flame source is removed (UL 94 applies).
- Flame‑resistant: Resists ignition entirely; tested under other standards (e.g. ASTM D6413, ISO 15025) – commonly used for textiles/PPE.
Which flame‑retardant materials are available from Konlida and what about PFAS/environmental concerns?
We offer numerous UL 94‑rated resins for injection moulding and select flame‑retardant options for 3D printing (e.g. Arkema FR512 achieves V‑0 at 0.79 mm). Customer‑supplied resins can be evaluated on request. Some FR systems may include PFAS or halogenated additives; we monitor regulations and can help confirm resin composition or explore non‑halogenated alternatives to support recyclability and environmental goals.