What Is UL-94 V-0? Selecting Flame Retardant Plastics

UL-94 is a globally recognised flammability standard that classifies the burning behaviour of plastic materials. It is frequently required as a precondition for part approval, particularly in the electrical and electronics sector.

The standard evaluates whether the material self-extinguishes once the flame source is removed and whether it produces flaming drips.

There are three main classes in the vertical burning test. V-0 is the highest, most demanding class: the shortest extinguishing time is expected after the flame is removed, and flaming drips are not permitted.

V-1 allows a longer extinguishing time but still permits no flaming drips. V-2 is similar to V-1 in extinguishing behaviour but permits drips that ignite the cotton indicator.

So when a customer specification says "V-0", it signals that not only extinguishing speed but also dripping behaviour is critical.

The most common mistake is thinking of the class independently of thickness. A UL-94 class always applies to a specific specimen thickness. A material may achieve V-0 at a thicker section and fail to achieve the same class in a thin wall.

The question is therefore not "is it V-0" but "at what thickness is it V-0". This information is in the grade's technical data sheet and its UL Yellow Card listing.

Flame retardancy can be achieved through different additive systems. Halogenated systems are effective, but many projects now require halogen-free solutions due to environmental regulations and customer policies.

Halogen-free systems are typically phosphorus based and can affect the mechanical and thermal properties of the material differently. If a halogen-free requirement exists, stating it at the start of the project speeds up correct grade selection.

In electrical and electronic applications, flame retardant PBT, PC, mPPO and polyamide compounds are the most common choices. mPPO alloys stand out for halogen-free flame retardancy and dimensional stability; PBT is widespread in connectors and coil bobbins.

High-performance materials such as PPS can reach a high flammability rating inherently, without additional additives.

When UL-94 class, thickness, halogen-free status and colour requirements are considered together, the list of suitable grades narrows quickly. Share your specification with us and we will identify suitable alternatives from the LG Chem and Basechem portfolio, with official TDS and sample support.