UL Yellow Card in the automotive industry

The UL Yellow Card is a widely used technical reference in materials engineering for selecting plastics in demanding applications.

In sectors such as automotive, where safety, thermal resistance and fire behaviour are critical, this tool allows engineers to work with previously tested and recognized materials, reducing uncertainty in key project phases.

What is a UL Yellow Card in the automotive industry?

A UL Yellow Card is a technical datasheet issued by Underwriters Laboratories (UL) provides recognition of a specific plastic material after it has been tested under different standards. 

It is the certificate issued by Underwriters Laboratories (UL) that documents how a plastic or resin behaves when exposed to fire.

It is not an automotive-specific regulation, but rather a technical tool used across multiple industries such as electrical, electronics, lighting, industrial equipment, and white goods (household appliances).  

Its main function is to provide validated information about material performance, particularly in relation to flammability, temperature resistance and other properties relevant to technical applications. 

In automotive, it is used as a supporting criterion when selecting materials for components where safety and stability are critical factors.

In component design (such as engine parts or wiring), manufacturers need to know whether the material is safe in the event of overheating or a short circuit. 

What technical information does a UL Yellow Card provide?

A UL Yellow Card includes key information that allows quick evaluation of a material’s suitability:

• Material identification and manufacturer
• Specific commercial grade
• Flammability classification according to UL 94
• Tested thicknesses
• Relative Thermal Index (RTI): Measures the thermal degradation of the material when exposed to heat over the long term. 
• UV/Weather Exposure (f1): Certifies that the plastic maintains its flame-retardant and mechanical properties when exposed to sunlight and water. 
• Other recognitions or relevant certifications

These data points enable comparison between materials and support informed decision-making in early design stages.

Why it matters to B2B manufacturers of technical components

For B2B manufacturers, the UL Yellow Card is a tool that improves efficiency and reliability in product development:

• Reduces uncertainty in design, procurement and quality processes
• Facilitates selection of materials with known performance
• Accelerates industrialization processes
• Cost and time savings: It avoids the need to perform destructive fire tests every time a new part is designed, as the card certifies the material’s behavior at different thicknesses. 

It is important to note that it does not replace final component validation, but it does guide material selection effectively.

The relationship between UL Yellow Cards, UL 94 and flame-retardant plastics

UL 94 evaluates the flammability behaviour of plastic materials.

The UL Yellow Card compiles this classification for a specific material, along with additional technical data.

This relationship is particularly relevant in the use of flame-retardant plastics, which are widely used in automotive applications such as electrical and electronic components or areas exposed to heat.

The Yellow Card helps verify that a material meets the required safety levels.

What classifications such as HB, V-2, V-1 and V-0 mean

UL 94 classifications indicate different levels of resistance to combustion:

• UL94 HB (Horizontal Burning): Basic level, the material burns slowly in a horizontal position. Low resistance, not recommended for high-risk areas. 
• UL 94 V-2: The material self-extinguishes but may produce flaming drips
• UL 94 V-1: Improved performance compared to V-2, with reduced flame propagation and limited dripping
• UL 94 V-0: Highest level, the material self-extinguishes quickly without flaming drips. The plastic self-extinguishes within a maximum of 10 seconds after the flame is removed. It is the most stringent and commonly used rating in the automotive sector, especially for electrical and battery components. 

In automotive applications, V-0 is typically the reference level for components requiring higher fire safety, especially in electrical and electronic parts.

Why component wall thickness matters as much as the material itself

A key aspect is that UL 94 classification depends on the tested thickness. The same material can behave differently depending on its thickness.

This has direct implications for design:

• Thin-wall components may not achieve the same classification
• Housings, connectors and injection-moulded parts require specific validation
• Geometry influences the final safety performance

Therefore, material and design must be evaluated together.

The difference between UL Yellow Cards, UL 94 and FMVSS 302

It is essential not to confuse these concepts:

• UL Yellow Card: Technical document that compiles recognized material properties
• UL 94: Standard that classifies plastic flammability
• FMVSS 302 (Federal Motor Vehicle Safety Standard 302): Automotive regulation applicable to interior vehicle materials

They are not equivalent or interchangeable, but complementary within the validation process.

When FMVSS 302 applies in automotive applications

FMVSS 302 applies to materials used in the vehicle interior, such as:

• Trim materials
• Panels
• Seats
• Coatings
• Interior elements

It evaluates flame propagation speed under specific conditions

It does not replace UL 94, but rather addresses specific regulatory requirements in the automotive sector.

Applications of UL Yellow Card materials in automotive and technical industries

Materials with a UL Yellow Card are used in a wide range of applications requiring high technical performance:

• Equipment housings
• Cable support
• Wire guides 
• Electronic enclosures
• Structural supports 
• Components exposed to heat
• Under-the-hood parts
• Industrial equipment

They are commonly used in environments where heat, electricity or fire risk are critical factors.

Electrical, electronic and heat-adjacent components

In these applications, material selection directly impacts:

• System safety
• Thermal stability
• Flame propagation resistance
• Long-term reliability

Components such as connectors, electronic modules or technical housings require materials with validated behaviour, where the UL Yellow Card serves as a key reference.

What companies should review before manufacturing a component with a UL Yellow Card material

Selecting a V-0 rated material is not enough. Several variables must be reviewed before manufacturing:

• Exact material grade
• Specific supplier
• Actual component thickness
• Real operating conditions (temperature, environment, load)
• Project requirements and standards

Incomplete evaluation can lead to design failures or non-compliance.

Material selection, component design and the injection moulding process

Final performance depends on the interaction between:

• Material: thermal, mechanical and flammability properties
• Design: thicknesses, ribs, geometry, tolerances
• Process: injection parameters, shrinkage, dimensional stability

An integrated approach allows optimization of both safety and industrial feasibility.

The role of a technical manufacturing partner such as OSF

Working with a specialized technical partner is key in complex projects. 

OSF offers direct manufacturing of components in technical plastics, elastomers, fluoropolymers and LSR, providing:

• Expertise in material selection
• Technical support in design and industrialization
• Capability to operate in demanding environments
• Agile communication in B2B projects

In a context where technical precision is essential, partnering with an experienced manufacturer helps reduce risks and accelerate product development.