DAF KEUR 00821-020 Dimensional Stability After Thermal Aging

The “DAF KEUR 00821-020 Dimensional stability after heat aging” standard, developed as part of the official approval or certification process for parts, materials, or processes used in trucks manufactured by DAF, a Dutch truck manufacturer, describes a procedure for determining the dimensional stability of plastic parts at high temperatures without external mechanical loading.

DAF's own series of internal material and component testing standards ensures that interior and exterior materials (such as plastics, textiles, coatings, and upholstery panels) used in truck cabs meet the demanding durability, safety, and performance requirements for heavy-duty commercial vehicles.

The DAF KEUR 00821-020 standard evaluates the dimensional stability of materials after exposure to thermal aging. This is particularly critical for interior components such as instrument panels, door panels, seats, headliners, and other plastic or composite parts that can be exposed to high temperatures inside a truck cab, especially in hot climates or with prolonged exposure to sunlight.

This testing method checks how much a material changes in size (shrinkage, expansion, bending, or deformation) over time when exposed to high temperatures. Excessively deformed materials can lead to fit issues, gaps, rattling, aesthetic deterioration, or even functional problems in a vehicle's interior.

This standard belongs to the broader KEUR 00821 series, which focuses on material specifications for interior applications in trucks. Related standards in this series include:

• DAF KEUR 00821-024 Resistance to mold growth (mold/fungus resistance on interior panels).
• DAF KEUR 00821-025 Cleanability of interior panels.

Other standards in this series generally cover aspects such as resistance to environmental factors in truck cabs.

Heat aging dimensional stability tests in the automotive and trucking industries typically follow these common practices:

• Sample preparation: Standardized test samples are cut from the material (e.g., plastic sheets or molded parts).
• Initial measurement: Precise measurements of dimensions (length, width, thickness) are taken using instruments such as calipers or optical systems.
• Heat exposure: Samples are placed in a controlled oven or climate chamber at a specific temperature (typically 80-120 degrees or higher, depending on the material grade) for a specified period of time (e.g., 24 hours, 168 hours, or longer).
• Conditioning: After the samples are removed, they are left to cool and recondition at standard room temperature and humidity.
• Final measurement: Dimensions are measured again and the percentage change is calculated.
• Acceptance criteria: DAF defines the maximum permissible dimensional change (e.g., linear contraction/expansion), visual defects, or distortion limits.

Similar tests are generally compatible with or based on international standards such as “ISO 188 Rubber, vulcanized or thermoplastic - Accelerated aging and heat resistance tests” or “ISO 2796 Cellular plastics, rigid - Dimensional stability test”, but adapted to truck-specific conditions (higher thermal loads, longer service life expectations).

Trucks operate in extreme conditions: heat from engines, prolonged idling, cabs exposed to the sun in summer, or temperature fluctuations. Materials must maintain their shape and integrity for 10-15 years. Deterioration of dimensional stability can be caused by:

• Misaligned panels or gaps.
• Increased noise and vibration.
• Decreased perceived quality.
• Need for early replacement.

DAF suppliers must demonstrate compliance with DAF KEUR 00821-020 and related standards in their part approval processes. This standard plays a crucial role in ensuring the long-term reliability and quality of truck interiors.

Heavy-duty trucks, such as those manufactured by DAF, operate in much harsher thermal environments than typical passenger cars, and their interior materials must maintain their shape and performance for very long service lives (typically 10-15 years or 1-2 million kilometers). This is why this standard is necessary. The main reasons for the need for this standard are as follows:

• Extreme and prolonged heat exposure in truck cabs: Interior surfaces (e.g., instrument panels, door panels, headliners, console covers, seatbacks made of plastic, composite, textile, or coated materials) can reach temperatures of 80–110 degrees Celsius for extended periods. Many polymers and composites that do not have good heat resistance are subjected to various adverse conditions. This standard simulates these conditions through controlled heat aging and measures linear dimensional change (shrinkage/expansion), bending, or deformation.
• Over time, fit, clearance, and assembly quality: Truck interiors feature large, visible panels and tight tolerances for a superior feel and low noise/vibration. Excessive dimensional variation creates visible gaps, misaligned flooring, protruding edges, or rattling parts. In the worst cases, warped panels can obstruct controls, airbags, HVAC vents, or safety features.
• Durability and total cost of ownership: Suppliers must demonstrate during part approval that the materials meet the DAF KEUR 00821-020 standard (along with relevant standards such as DAF KEUR 00821-024 for mold resistance or DAF KEUR 00822-115 for aging resistance).
• Features specific to commercial vehicle expectations: Unlike cars (where interiors may have a shorter lifespan or be exposed to extremely harsh conditions), trucks require the following:
• Longer warranty periods for indoor applications.
• Higher resistance to environmental cycles (heat, humidity, UV).
• Materials resistant to post-forming shrinkage, commonly used in injection-molded or thermoformed plastics for large cabinet components.

DAF's KEUR series of standards goes beyond general automotive norms (e.g., ISO 188 or PV 1303 heat aging tests) with stricter limits or conditions.

In short, the DAF KEUR 00821-020 standard prevents heat-induced dimensional changes that could compromise the long-term compatibility, function, appearance, and reliability of the truck cab interior. This directly impacts driver comfort, perceived quality, warranty costs, and the resale value of the truck for fleet operators.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its customers, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services to businesses in accordance with the DAF KEUR 00821-020 standard.