Ensuring unpainted automotive exterior parts withstand UV weathering

Painting exterior parts provides a high-quality surface that protects the substrate from UV weathering. Yet it is a very costly process – both in terms of production costs, and its effects on the environment. During the drying process, solvent-borne paints release volatile organic compounds (VOCs) into the atmosphere, leading to increased air pollution, fine particulate matter and smog.

To help reduce environmental impacts and productions costs, car manufacturers are looking to eliminate paint wherever possible by replacing painted exterior plastic parts with unpainted versions.

Meeting stringent UV weathering standards

Without the protective paint layer, the materials used in these applications need to demonstrate extreme UV weathering resistance. They also need to maintain excellent mechanical properties, provide a highly aesthetic finish and be easy to process using complex molding techniques, such as overflow or short shot gas assist injection molding.

DSM’s Akulon GA-XL portfolio of polyamide 6 (PA6) grades meets stringent UV weathering conditions to provide OEMs with the option of designing unpainted exterior parts and trims. The portfolio includes grades engineered for a range of different UV requirements, part complexities, and molding processes, with an optimal balance between price and performance.

Available in both 30% and 50% glass reinforced versions, the grades provide excellent UV resistance, passing some of the most stringent UV weathering tests prescribed by the automotive industry today – including SAE J2527 up to 3,000 hours and the Florida test. The grades can be produced at lower injection pressures using the same molding machines as standard grades, with less tool wear and no flow marks. Their broad processing window allows for more freedom in part design.

The 30% glass filled grades are suitable for exterior applications, such as gas assist door handles, while the 50% glass reinforced grades can replace metal or polyphthalamide-based (PPA) solutions in semi-structural applications that require a combination of strength, stiffness and superior surface appearance.

The Akulon GA-XL grades demonstrate better molding performance than standard PA6 grades in overflow gas injection processes. For short shot gas injection technology, the materials provide faster cycle times while demonstrating less volumetric shrinkage and part deflection compared to other popular materials for short shot door handles, including PC/PET blends.

Talk to our engineers today about how to ensure your next unpainted part design can withstand extreme UV weathering while reducing processing costs.

Durgesh Bakshi

Global Product Development Specialist for Performance Polymers at Envalior

Envalior