Thermoplastic Materials Save 10% Weight for Reanult

4th October 2012

Styron, a global materials company and manufacturer of plastics, latex and rubber, has unveiled the first full-thermoplastic, mono-material lift-gate ever produced in series on a commercial vehicle featured in the New Renault Clio. As a result, the new lift-gate has achieved a 10% reduction in component weight.

After a two-year development project with Styron, Renault is now launching the New Renault Clio with a thermoplastic lift-gate made with Styron’s material solutions. The lift-gate is manufactured in thermoplastic from three separate parts.

“The automotive industry has been looking for alternatives to steel for lift-gates for many years. Weight savings, styling freedom and function integration are the main objectives,” says Marjolein Groeneweg, Marketing Manager Styron Automotive. “With this innovative concept jointly developed by Renault and our R&D department, the French car manufacturer not only contributes to weight reduction for optimal fuel efficiency but also responds to waste management recycling guidelines promoting recyclability without disassembly. Knowing that the base polymer of the lift-gate solution is the same, the part can be easily recycled and used in other future applications.”

 

Image of the inside skin and final design of the tail-gate

 

A lift-gate is a complex application for several reasons: It needs to fit perfectly on to the car and has numerous functions that need to be hidden (such as the hinges and the closing mechanism). Additionally, it is subjected to many external conditions such as exposure to high/low temperature in humid environment that can cause deformation issues and must then be addressed to guarantee water tightness. To help improve impact resistance, expansion and durability of the structural part of the lift-gate, Styron’s engineers introduced INSPIRE™ long glass fiber polypropylene resin (LGF-PP) to meet such requirements. By increasing the glass content of the molding material, the part is able to gain improved stiffness and toughness.

In addition, Styron also supported Renault in optimizing the tool-design for their machine and specifically supported them with selecting the appropriate plasticizing screw to maintain the required fiber length after moulding the lift-gate. Choosing a material composition and manufacturing process that achieves the desired glass fiber length distribution is critical to meeting the specific performance requirements of Renault’s lift-gate.

In the realization/production phase, Styron has offered both material development and processing support. In the selection of the materials, Styron was confronted with several challenges due to the complexity of the part. The selected materials were tested and fine-tuned to Renault’s specific production process including injection molding, painting, bonding and welding. The final lift-gate design consists of three parts:

  • The inner skin is injection moulded using a talc filled polypropylene compound from Styron and connects to the structural part.
  • The structural part is produced with long glass fiber polypropylene resin (LGF-PP) concentrate developed by Styron. This concentrate is diluted directly on the moulding machine with appropriate PP copolymer resin through dry-blend directly.
  • The outer skin is made with Styron’s INSPIRE™ At-Press talc masterbatch concept, which injection moulds through blending of the different components (polypropylene impact copolymer, specifically designed 70% talc masterbatch and the required color concentrate), allowing for a tailored mechanical performance to meet the OEM specific application requirements.

The final design of the successfully reduced the weight of the tail-lift by 10% when compared to a metallic alternative.

 

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