Currently, there are numerous automotive interior and exterior trim components, including instrument panels, console panels, headliners, seats, seat belts, door trim panels, pillar trim panels, and luggage compartment trim pieces. Due to inherent structural or compositional vulnerabilities within the materials, such as the presence of unsaturated double bonds, branched chains, carbonyl groups, and terminal hydroxyl groups, these components are prone to photo-thermal aging when exposed to environmental factors like light, heat, moisture, and oxygen. This can lead to aesthetic degradation or functional failure. This article delves into the causes of aging in automotive interior and exterior trim materials, the testing standards and requirements for lightfastness, and strategies to mitigate or prevent aging phenomena during the early stages of material development.
Aging Performance of Automotive Interior Components:
Automotive interior components are subjected to varying degrees of sunlight and thermal exposure depending on their location within the vehicle. Consequently, the effects of light and heat differ among components. Aging typically manifests in the following ways:
- Surface Defects: Cracking, chalking, deformation, spotting, whitening, blistering, and other defects that compromise the appearance quality of the components.
- Physical Property Changes: Degradation and crosslinking reactions in the interior and exterior trim materials alter their physical characteristics, affecting molecular arrangements such as unsaturated bond breakage. These changes influence material properties like density, temperature, melting point, solubility, glass transition temperature, and thermal conductivity.
- Mechanical Property Changes: Degradation and crosslinking reactions impact hardness, tensile strength, shear strength, notched Izod impact strength, flexural modulus, elastic modulus, and the adhesion of surface coatings or plating, potentially leading to paint or plating peeling or detachment.
- Electrical Property Changes: Degradation and crosslinking reactions in the materials affect their insulating properties, dielectric constant, dielectric loss, and breakdown voltage.
UV Aging Test Standards for Automotive Interior Components:
Automotive interior component aging tests simulate the damage caused by sunlight penetrating through window glass and subsequent thermal effects. A multitude of testing standards exist, with significant variations among them. Selecting the appropriate standard depends on the test objectives, duration, and material type. Commonly referenced standards include ISO 105-B02, ISO 105-B04, ISO 105-B06, ISO 105-B10, SAE J2412, ASTM G155, ISO 4892-3, ISO 16474-3, ISO 4892-2, ISO 16474-2, SAE J2412, and ASTM G155. Users can choose the most suitable standard based on material requirements, test purposes, and time constraints.
Toyota's Aging Test Standard for Automotive Interior Components:
TSM 0501G is one of Toyota's series of testing standards, specifically addressing the standard test methods for plastic molding materials used in automobiles. It outlines the testing requirements for the outdoor weather resistance and lightfastness of plastic components. During the light exposure cycle, the relative humidity is maintained at 50%, with an irradiance of 0.55 W/m²/nm, a black panel temperature of 89°C, and an air temperature inside the chamber of 62°C, lasting for 24 hours.
Common Aging Equipment for Lightfastness Testing of Automotive Interior Components:
Laboratories conducting lightfastness aging tests for automotive interior components commonly employ Q-SUN xenon arc weatherometers and QUV ultraviolet accelerated weathering testers. Q-SUN xenon arc weatherometers utilize window glass filters to simulate the damage caused by sunlight on automotive interior components. QUV ultraviolet accelerated weathering testers employ UV lamps, with UVA-351 lamps being suitable for aging tests on automotive interior materials.
