Seattle, WA, USA--(Jobwerx News)--Basf and NylonCraft develop the first automotive exterior trim component using an innovative two-shot, plastics injection molding process, along with a creative tooling design.

BASF, New Jersey and NylonCraft, Mishawaka, Ind., have jointly developed the first auto trim exterior component using a combination of acrylonitrile-styrene-acrylate (ASA) and thermoplastic elastomer (TPE) in North America. The ‘two-shot’ rear quarter window reveal exterior part meets aesthetic requirements.

The unique combination of BASF’s Luran® S ASA and TPE used in an innovative “two-shot” plastics injection molding process, along with a creative tooling design, resulted in a component that met the automotive manufacturer’s demanding aesthetic and performance requirements, as well as cost and quality targets.

“We tested about 12 TPE/substrate combinations. Typical two-shot substrates, such as olefins, did not meet the functional specifications like weathering performance. Other candidate resins were chemically incompatible, and therefore less bondable, with standard TPE resins and did not meet the stringent interface adhesion requirements,” said Rollie Erb, Vice President of Sales and Engineering for NylonCraft.

“Process control is critical to achieving cost and quality targets, so introducing additives in the process to compensate for these deficiencies wasn’t a solution,” Erb said. “Adding in adhesives caused process sensitivities and unacceptably diminished the plastics part’s aesthetic properties, and using color concentrates negatively impacted the adhesion of the candidate resins to the TPE.”

According to Erb, Luran S ASA provided the best combination with TPE for adhesion, flow, ultraviolet (UV) resistance, dimensional stability and appearance to produce the window reveal part.

“The two-shot process and the color stability properties of Luran S ASA eliminated the need to use basecoat to achieve precise color matching. The compatibility of the two resins plus the interface design also accomplished maximum adhesion in the process without the need to introduce an adhesive. Removing the need for additives in the process enables us to better control the parameters for optimally producing the finished part,” said Erb.

The inherent superior weathering characteristics of BASF’s Luran S ASA allow the introduction of “molded-in-color” automotive components, thereby providing designers with more options than black. For this application, BASF’s Luran S ASA achieved the automotive manufacturer’s precise specifications for color matching and harmony with mating components, including a clean interface line between the ASA and TPE materials, and meeting surface requirements.

“The window reveal is a long component that requires dimensional stability in all temperatures and conditions, which is why the weathering performance requirements for this application are stringent,” Erb said. “Having Luran S ASA completely encapsulate the entire edge of the TPE core enables the rear lift gate trim to withstand expansion in summer heat and maintain its integrity in cold temperatures, while making the component resistant to fading. The two shot system eliminates the need to add a secondary seal to the system.”

In addition to the compatibility of BASF’s Luran S ASA and TPE, the ability to meet the automotive manufacturer’s requirement for part adhesion specifications beyond standard levels was achieved through an innovative plastics part design.

NylonCraft developed a “lap joint” through creative tooling in the injection molding to increase the surface area, as well as a small rib extending along the TPE component to increase contact between the materials. This resulted in a stronger adhesion and an improved high strength performance for the plastics component. This seal and substrate geometry also optimized aesthetic properties and improved the rear quarter window reveal trim’s thermal stability performance.

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