27 July 2012 00:00 [Source: ICB]
Polymer makers put the pedal to the plastic when it comes to automotive market development
Materials have been the backbone of the automotive industry, which is being impacted by CO2 emission legislation. To combat this, engine downsizing, turbo-charging and light-weighting are the global trends that are affecting the choice of materials.
A 10% reduction in vehicle weight results in a 5-7% fuel saving, provided the power train is downsized (or a 3-4% fuel saving without power train modifications). 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. 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.
Metals, owing to their strength, recyclability and good cost-to-performance ratios, have historically been the preferred choice for structural components. For a typical mid-size passenger car, metals constitute about 75% of vehicle weight, of which around 60% is traditional and high-strength steels and 7% is AHSS. Aluminum occupies around 89% by weight and is expected to exhibit healthy growth as it competes with steel and plastics in almost all components of a car. Magnesium (in alloy form), exhibiting the highest strength-to-weight ratio among structural metals, is also set to grow.
PLASTICS: OFFERING MORE FOR LESS?
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. Regional variations can be seen in plastic usage, which Europe leads at as high as 11% 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.
UNDER THE HOOD
Under-hood components, such as air intake manifolds, engine covers, radiator end tanks, valve covers and oil pan modules are fabricated using PA6 and PA66 owing to their light weight, temperature and chemical resistance.
Polyphenylene sulphide (PPS) performs better than PA, in these terms, and represents a strong candidate for original-equipment manufacturers (OEMs) as a metal replacement in order to reduce vehicle weight. The only current disadvantage is its premium price.
PP finds applications in interiors such as dashboard, dashboard carriers, pillar cladding, door pockets, door panels, consoles and chairs.
Bumpers, bumper spoilers, roof/trunk spoilers, lateral sidings, rocker panels, body panels and wheel arch liners are exterior applications for PP. PP accounts for around 64kg (141lb) of vehicle content and this is expected to grow to 84kg by 2017, as reinforced PP is expected to replace metals in some under-hood and exterior parts (such as tailgates). It is also replacing PU foam in seating applications, where hybrid PU-PP foams are being used.
Most applications of PA are found in under-hood components. In the interior segment, door handles, parts of air bag assembly, instrument panels, levers for seats and pedals use PA6 and PA66. The average content of PA is around 11kg and is expected to grow to 13kg by 2017, replacing polymers such as PPS for under-hood applications, for example in charge air ducts. In exterior applications, PA is used where the plastic does not need to meet Class-A (high aesthetic quality) surface requirements.
PU as foam captures seating applications with little competition.
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.
The average vehicle content of PU is around 23kg. PU foams occupy around 55% while rigid PU occupies the rest.
However, this particular plastic is facing a significant substitution threat from PP. The average ABS content is therefore expected to fall from 10.5kg to 9.5kg. ABS will remain the plastic of choice in applications where paintability or adhesion to other surfaces is required.
Because of the substitution threat, the ABS market is expected to grow more slowly than the vehicle production rate.
The thermoset market is seeing a mixed response from OEMs, owing to end of life vehicle legislation and the consequent recyclability issues. While companies like Japan's Nissan, Italy's Fiat and US groupChrysler are moving away from thermosets due to legislation, BMW has opted for carbon fiber reinforced composites for the chassis of its new BMW Megacity vehicle. 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.
The consumption of thermosets per vehicle is expected to decline to under 4.0kg from 4.2kg, due to increasing competition from aluminum.
Globally, demand for plastics in passenger vehicles is set to grow to 9.1m tonnes by 2017 from 5.5m tonnes at present, with PP showing the fastest growth. 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.
Shree Vidhyaa Karunanidhi is a Research Analyst at Frost & Sullivan's Chemicals, Materials and Food Practice, focusing on trends in the automotive industry. For further information, please contact firstname.lastname@example.org
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