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Light weight and high performance materials, bioplastics drive developments in automotive industry

Light weight and high performance materials, bioplastics drive developments in automotive industry

31-Aug-12

Driven by CO2 emission legislation, environment regulations and growing consumer awareness worldwide, the global automotive industry continues to strive towards greater fuel efficiency. The drive for greater fuel efficiency leads to light weighting that augurs well for the polymer industry. Penalties for excess emissions from vehicles have ensured that manufacturers use every material as a design variable to ensure that vehicle weight is reduced, with no compromise on safety and performance. As per ICB in ICIS, a 10% reduction in vehicle weight results in a 5-7% fuel saving, if the power train is downsized (or a 3-4% fuel saving without power train modifications). Material studies have shown that aluminum, advanced high-strength steel (AHSS), and some plastics like polypropylene (PP), polyamide (PA) and polyurethane (PU) have emerged as preferred choices for light-weight design. The inherent features of plastics have been major drivers for their use in vehicles. These include light weight, lower tooling costs for high volumes and the possibility to be fabricated as a single complex component, eliminating the need for mechanical fasteners. A typical passenger car's plastic content is 8% of vehicle weight with Europe leading at as high as 11% plastic content of vehicle weight. Vehicle interior plastics occupy 48%, exterior plastics account for around 27% and under-hood plastics around 14% of the total plastics used. Electrical and cable materials occupy the remaining 11%. Under-hood components offer good margins and high penetration potential, particularly in Asia and Latin America. In the mature markets, like North America and Europe, plastics are finding inroads into newer interior and exterior applications. Globally, demand for plastics in passenger vehicles is set to grow to 9.1 mln tons by 2017 from 5.5 mln tons at present, with PP showing the fastest growth, as per Frost & Sullivan. Plastics demand from the automotive industry is set to grow and significant research is being carried out by OEMs, part manufacturers and plastics producers to develop high performing, high strength plastics and to find new applications for these materials. Although plastics are light-weight and have other advantages, strength is lacking and needs to be addressed in order for plastics to be used in more demanding and structural applications. Plastics have a long way to go to exhibit similar demand to metals, which constitute the bulk of materials for automotive construction. The industry is seeing development of high strength plastics, such as polyoxymethylene (POM) for components such as gears, but they do not offer a cost-effective solution, as metal does. Thus, a balanced set of properties strength, crash-resistance and cost needs to be exhibited by plastics to see greater adoption in the future.

As per ICB in ICIS, polypropylene is used in interior, exterior as well as under hood parts. Bumpers, bumper spoilers, roof/trunk spoilers, lateral sidings, rocker panels, body panels and wheel arch liners are exterior applications while dashboard, dashboard carriers, pillar cladding, door pockets, door panels, consoles and chairs are interior applications for PP. Currently, PP accounts for around 64 kg (141 lb) of vehicle content, estimated to grow to 84 kg by 2017. The rise in PP consumption will be driven by increasing application of reinforced PP as a replacement for metals in some under-hood and exterior parts, as well as a replacement for PU foam in seating applications. PA6 and PA66 offer light weight, temperature and chemical resistance to underhood components such as air intake manifolds, engine covers, radiator end tanks, valve covers and oil pan modules. The average content of PA is around 11 kg and is expected to grow to 13 kg by 2017. In the interior segment, door handles, parts of air bag assembly, instrument panels, levers for seats and pedals use PA6 and PA66. In exterior applications, PA is used where the plastic does not need to meet Class-A (high aesthetic quality) surface requirements. Comparatively, polyphenylene sulphide (PPS) performs better than PA, and is a strong contender for automotive component manufacturers as a metal replacement that results in vehicle weight reduction. However, its currently high levels of pricing is a drawback and limit its use. Polyurathane finds application in seating foam and has barely any substitution. The average vehicle content of PU is around 23 kg. PU foams occupy around 55% while rigid PU occupies the balance 45%. Flexible PU foams are most common, while rigid PU foams are used in niche applications, such as noise, vibration and harshness materials and insulation. PU is used in seats, door skins, boot lining trays, parcel shelves, center consoles, dashboard trims, spare wheel trays, steering wheels, carpet backing and headliners. Acrylonitrile butadiene styrene (ABS) finds applications largely in interiors, such as interior grills, trims, headliners and center consoles. However, ABS faces a significant substitution threat from PP. The average ABS content is therefore expected to fall from 10.5 kg to 9.5 kg. ABS will remain the plastic of choice in applications where paintability or adhesion to other surfaces is required.
End of life vehicle legislation and the consequent recyclability issues have led to a mixed response from OEMs for the thermoset market. The consumption of thermosets per vehicle is expected to decline to under 4 kg from 4.2 kg, due to increasing competition from aluminum. Exterior Class-A body closures/panels like fenders, hoods and decklids will remain the main applications for thermosetting composites, as they showcase excellent strength and low weight. Non-compostable, bio-based materials are being increasingly used by several leading automotive manufacturers. However, weight advantages are not assured with every switch to these environment friendly materials. Reduced dependence on volatile energy markets is one of the benefits of bioplastics.

 
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