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Issue 01/2016

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Automotive Foam Basics: Public Procurement


Automotive Lightweighting is key Reaching lightweighting goals with new natural fiber reinforced solutions Charpy unnotched Flexural modulus 100 % 80 % 60 % 40 % 20 % 0 % Tensile strength Flexural strength Tensile modulus Tensile elongation Coupling Technologie 1 Coupling Technologie 2 Graph 1: Performance comparison between the two coupling technologies on Natural Engineered Fiber 1 Graph 2: Comparison of reSound NF 40% natural fiber reinforced solution vs. ultimate target profile Specific gravity 100 % HDT A HDT B Charpy unnotched impact strength 80 % 60 % 40 % 20 % 0 % Flexural modulus Ultimate target Results Tensile strength at break Tensile modulus Flexural strength at break Manufacturers of semi-structural automotive applications now have the option to reduce part weight by 5 % or more, maintain mechanical performance, and even use more sustainable materials. A triad of developments makes this possible. Automobile manufacturers need to improve their vehicles’ fuel efficiencies, as required by global regulations. Reducing a vehicle’s weight is one of the most direct ways to improve fuel efficiency. Not only do lower-weight vehicles use less fuel, but they also generate lower carbon dioxide (CO 2 ) emissions. For carmakers marketing their vehicles in Europe, failure to reach incremental CO 2 limits imposed by the European Commission would force OEMs to pay a significant penalty of up to 95 € per gram of CO 2 over the limit and for each new car sold. PolyOne recognized the challenges these new regulations placed on manufacturers in the automotive industry and set out to develop a solution that could meet the mechanical properties of parts made with short glass fiber reinforced polypropylene (GFR-PP), but with a density at least 5 % less than that of GFR-PP. The Company targeted more than 20 demanding automotive applications; many of these are large parts, such as instrument panel carriers and lighting systems, so a 5 – 10 % reduction in density could lead to significant overall weight reduction. A reduction of this magnitude is what automotive customers said was necessary for them to consider alternate materials to those already proven suitable for commercial use. PolyOne’s search for a solution to the lightweighting challenge led to the development of a new natural fiber reinforced thermoplastic (NFR-TP) that supports lightweighting goals in the automotive and other industries, while also maintaining the necessary mechanical performance characteristics. Develop a novel compounding process The Company is one of the world’s leading developers of thermoplastic compounds, with research and development experts at laboratories around the world. As the process to develop a lightweight replacement for GFR-PP began, the experts there recognized that a new type of compounding process showed promise for the manufacture of strong, stable compounds even with materials of different polarities. R&D teams at PolyOne had been working for two years to optimize the process, and believed this new compounding technology could be key to manufacturing NFR-TP solutions with excellent mechanical properties. It seemed a critical part of the solution to the long-recognized challenge of the ability of a non-polar thermoplastic material to couple with a polar reinforcing material. 12 bioplastics MAGAZINE [01/16] Vol. 11

Automotive This new compounding technology proved to be the first leg in the triad of developments that led to success. Find the best fiber for the job When it comes to reinforcing polypropylene with natural fiber, many routes, variables, and choices can have a significant influence on the final solution: • type of PP (homo- or copolymer) • melt index • type of reinforcing fiber • coupling technology • manufacturing process A design of experiment (DOE) helped reduce these input variables down to three: the type of fiber, coupling technology for the fiber and the PP, and manufacturing process (compound extrusion). PolyOne’s R&D experts already had developed what the researchers felt might be the best manufacturing process, but they needed to find the right materials. A PP homopolymer was determined to be the optimal matrix material with the appropriate melt index. So the best fiber for the applications targeted needed to be found, and a coupling technology to enable these fibers to bond well with the thermoplastic matrix material. Natural fibers made sense because of their low density; but to serve the automotive industry, fibers need to be available globally, with consistent sizing and quality. Testing of many types of natural fiber led to an engineered fiber, available globally as a modified product of an established wood fabrication industry. These fibers are supplied with consistent length and thickness, facilitating production of a compound with consistent properties – if the new compounding technology was able to evenly distribute the fibers throughout the matrix material, and helped create a powerful bond between fiber and matrix material. A powerful bond The best fibers would be worth little if they could not be properly mixed into and bonded with the thermoplastic matrix. PolyOne’s search for solutions to these challenges led them to a coupling technology that forged the necessary bond, as seen in Graph 1. Coupling Technology 1 is an advanced technology while Coupling Technology 2 is a more classical technology. Coupling Technology 1 was tested on multiple fibers but ultimately PolyOne settled on the natural engineered fiber mentioned earlier. Testing began to determine whether the positive results seen in lab testing could be maintained at commercial scale. In addition, it needed to be investigated whether the new compounding process had an influence on the property profile at various reinforcing fiber amounts (30 % and 40 % in weight). The properties of the material manufactured on industrial scale machinery are very similar to the original target, and realize a density reduction versus short glass fiber alternatives of at least 5 % (Graph 2). The new formulations were named reSound NF natural fiber reinforced solutions; reSound is PolyOne’s brand name for formulations that contain 30 % or more of renewably resourced materials. u By: Marc Mézailles Global Automotive Industry Manager, PolyOne Corporation Lyon, France Photo 1: Lightweight and strong: Tests have proven the mechanical performance of parts molded from reSound NF natural fiber reinforced solutions. bioplastics MAGAZINE [01/16] Vol. 11 13

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