Plastic Components with Flame Retardancy – Standards, Materials and Manufacturing Solutions

PPS | High-temperature FFF process | Application: Media guidance in machinery and equipment

Why Flame Retardancy in Plastics is Indispensable

Plastics have become indispensable in modern industry. They are lightweight, versatile, and economically manufacturable. However, a central risk remains: plastics are combustible. Especially in safety-critical sectors such as rail vehicles, aerospace, automotive industry, or medical technology, the use of flame-retardant plastics is essential. Standards such as DIN EN 45545-2, UL94V0, or FAR 25.853 define the requirements for materials that, in the event of fire, must not only be flame-resistant but must also exhibit low smoke and toxicity development.

Key Standards and Testing Methods

DIN EN 45545-2

EN 45545-2 (also frequently referred to as DIN EN 45545 2 or DIN EN 45545-2) is the central European standard for fire protection in rail transport. It defines which plastics may be used in the interior of trains in order to ensure the safety of passengers.

UL94 V0

UL stands for Underwriters Laboratories, an independent organization for the testing and certification of products regarding safety and standard conformity. The UL94 test classifies plastics according to their fire behavior. UL94V0 materials are considered particularly safe: after ignition they self-extinguish within seconds and do not form burning droplets. For many applications, a UL94V0 plastic is standard. In addition, there are further classifications. Here is a brief overview:

Class	Testing Method	Description (Criteria)
HB	Horizontal Burning	Horizontal specimen, burns slowly (<40 mm/min); lowest requirement
V-2	Vertical Burning	Vertical specimen, flame duration ≤30 s, burning droplets allowed
V-1	Vertical Burning	As V-2, but no ignition/no ignition due to droplets
V-0	Vertical Burning	As V-1, but critical: flame duration ≤10 s/per specimen, no droplets, no ignition
5VA / 5VB	Severe Burning	Very stringent vertical test, highest safety 5VB: specimen may develop a hole

FAR 25.853

In aerospace, FAR 25.853 specifies the criteria for combustible materials in aircraft cabins. Here as well, minimizing flame spread and smoke generation is of decisive importance. Within FAR 25.853, there are different test classes and classifications, depending on the type, installation location, and function of the plastic in the aircraft. Compliance is verified via specific fire tests with defined threshold values.

Materials with Flame Retardancy

Selecting the right materials is crucial for the safety and reliability of components. Here is an overview of proven flame-retardant plastics:

PA6: Good price-performance ratio, widely used in mechanical engineering and technical applications.
PA66: Higher heat resistance and strength than PA6, frequently used in electrical engineering.
PC: Impact-resistant polycarbonate with 10% glass fiber content, ideal for housings and structurally demanding applications.
PPS (inherently flame-retardant): Offers very good chemical resistance, used in electronics and automotive engineering.
PEEK (inherently flame-retardant): High-performance plastic with excellent flame retardancy, extremely temperature-resistant, commonly used in aerospace.
PPE: Low water absorption and good electrical insulation properties.
PEI: High-performance plastic with outstanding flame resistance, suitable for demanding applications in electronics and medical technology.

In addition, further polymers are available and can be obtained with corresponding fillers and reinforcing agents such as glass fibers or carbon fibers.

Inherently Flame-Retardant Plastics vs. Additive Flame Retardancy

Inherently Flame-Retardant Plastics

Certain high-performance plastics such as PPS or PEEK are inherently flame-retardant. This means that their molecular structure is, by nature, difficult to ignite. Reasons for this are:

High proportion of aromatic structures in the polymer base
Stable chemical bonds that do not readily break down when heated
Formation of a protective char layer that prevents the propagation of the flame

These materials often fulfill the highest requirements, such as UL94V0 or FAR 25.853, even without additives.

Combustible Plastics and Flame Retardant Additives

Other standard plastics such as PA6 or PC are easily ignitable without additives. In these cases, flame retardants are added to decrease combustibility. Typical mechanisms of action are:

Gas-phase mechanism: Additives release non-flammable gases (e.g. nitrogen, water) upon heating, which extinguish the flame.
Condensation mechanism: Flame retardants promote the formation of a stable char layer on the material surface, which prevents oxygen supply.
Radical scavengers: Certain additives interrupt the combustion chain reaction by neutralizing reactive radicals.

This makes it possible to achieve flame-retardant behavior in standard plastics such as flame-retardant PA6 or flame-retardant PA66 according to UL94V0.

Manufacturing Processes: Milling, Turning and 3D Printing

We offer the complete range of manufacturing processes for non-combustible plastic components:

CNC milling and turning: For precise components made from tested flame-retardant materials.
3D printing flame retardants: Especially interesting for prototypes or small batches. Thanks to state-of-the-art processes, UL94V0 plastic 3D printing is now also possible – ideal for rapid implementation of concepts.
LFAM technology: Large-format 3D printed parts with build envelope of 2500 x 1700 x 950 mm, using flame-retardant plastics and compounds.

Fields of Application

Rail vehicles: Components according to DIN EN 45545-2
Electronics: Housings made from UL94V0 plastic
Aerospace: Parts according to FAR 25.853
Mechanical engineering: Use of V0 flame-retardant plastics for increased safety

Your Partner for Safe Plastic Components

Whether milling, turning or 3D printing – we manufacture flame-retardant plastic components exactly according to the requirements of your sector. By complying with EN 45545-2, UL94V0 and FAR 25.853 we offer solutions that meet the highest safety standards.

Contact us if you are looking for a reliable partner who will develop and produce non-combustible plastic components for your applications together with you.