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        IMA

Automotive: New material innovations to spur lighter cars

Also, download this story from the electronic issue here

Fuel economy is the cornerstone of the current trend for lightweight cars, and emerging material technologies, such as cellulose nanofibres, ligninbased resins, lightweight composites and heat dissipating polymers, are enabling this trend, says Angelica Buan in this report.

The plexiglas body of Ford’s Pontiac in the 1940s has turned out to be a self-fulfilling prophecy more than 70 years later. Today, plastics are becoming an integral component of car building and support a global plastics market that will hit the US$54 billion mark by 2022, citing a report by Global Market Insights.

Car makers are required to address issues, such as fuel efficiency, as a matter of regulation. At the same time, they have to meet criteria for driving performance and affordability.

An important step to achieving fuel economy is to pare down the weight with plastics. For the industry, no reduction is too small.

Plastics typically contribute only about 10% reduction to the weight of the vehicle, and this can improve its fuel efficiency by as much as 8%. Hence cars, especially ones fitted with innovative features and systems made partly or entirely of plastics, account for the increasing demand for plastics.

Texas-headquartered consultancy IHS Chemical predicts that by 2025, plastic will represent a quarter of an Ford’s-Pontiac average car. The current rate of utilisation for polymers in automobiles runs at 700,000 tonnes, and this is likely to climb to 900,000 tonnes by 2020, according to IHS Chemical. It also adds that demand for carbon fibre, which is yet to expand adoption in the mainstream automotive industry, is anticipated to reach nearly 10,000 tonnes by 2030.

Current lightweight design techniques have parts, like bumpers, seats, dashboards, fuel systems, body panels, electrical components, interiors and others, made of plastics.

Polypropylene (PP) accounts for the largest share of the market share. It is followed by polyurethanes (PUs) and acrylonitrile butadiene styrene (ABS), according to research firm Persistence Market Research.

Light weighting with low-cost composites

Meanwhile, high performance composite materials promise improved performance at an even lower weight, as seen in a collaboration between India’s National Institute of Technology-Karnataka (NIT-K) and the US’s New York University that has resulted in the innovation of lightweight composites for automotive parts.

glass-microballoons-in-HDPE

The study, which reveals that plastics potentially reduce weight by as much as 36% but still lend better mechanical properties, involved an industry partner for industrial-scale manufacturing methods for producing composite specimens.

The composites studied by this team use hollow microspheres like fly ash cenospheres and glass microballoons in high density polyethylene (HDPE). “Hollow microsphere fillers can reduce the weight of the component, make them cheaper and reduce carbon footprint,” Dr Mrityunjay Doddamani of NIT-K said.

Doddamani, who led the research, said that the outcome will also debunk the perception that using composites is expensive. “Our effort has specifically shown that low cost composites can be developed by innovative use of materials and processing methods,” he stated.

The technology is also expected to benefit India’s small scale industries, which are mostly equipped with basic manufacturing machines for plastic moulding.

Doddamani explained that composite materials produced in controlled conditions in the laboratory cannot be replicated in industry conditions. However, with the technique developed, low-cost, light weight composites can be produced easily using standard compression moulding machines.

Pending commercialisation, the research team plans to cast prototype components and test them in actual applications.

Better than glass: heat-conducting polymers

Plastics and heat generally do not mix and, thus, plastics offer limited option in automotive and technology devices. While thermallyconductive plastics are not new, innovations in this category are getting better.

A latest breakthrough in heat-conducting plastic has been developed by a team of materials science and mechanical engineer researchers from the University of Michigan. The technique, according to their study titled High Thermal Conductivity in Electrostatically Engineered Amorphous Polymers, can change plastic’s molecular structure to dissipate heat.

plastic’s-molecular-structure-to-dissipate-heat

The process, which they said is inexpensive and scalable and engineers the structure of the material itself, could be applied to a variety of other plastics. Its preliminary test showed that the process can make the plastic as thermally conductive as glass, and six times better at dissipating heat than the same untreated polymer.

The study is bound to improve plastics used in electronics and car parts, which are inherently “poor heat conductors”. It is also expected to facilitate a better approach than adding metallic or ceramic fillers to plastic, which are expensive, can increase the materials weight and can change the properties of plastic in “undesirable ways”.

With plastic, heat has to travel along and between its labyrinthine long chains of molecules. The researchers used a chemical process to expand and straighten the molecule chains so that the heat energy is able to travel a more direct route through the material.

“Heat energy travels through substances as molecular vibrations. For heat to efficiently move through a material, it needs continuous pathways of strongly bound atoms and molecules. Otherwise, it gets trapped, meaning the substance stays hot,” said the researchers. Too, the process stiffens the polymer chains and helps them pack together more tightly, making them even more thermally conductive.

The processed involved linking polyacrylic acid (PAA) with short strands of polyacryloyl piperidine (PAP). The researchers explained that the new blend relies on hydrogen bonds that are 10 to 100 times stronger than the forces that loosely hold together the long strands in most other plastics. This technique will also be tested on other types of polymers, they said, noting that commercialisation is not yet prospected.

In the works is developing composites that combine the new technique with several other heat dissipating strategies to further increase thermal conductivity.

A spin on renewable fibres

Cellulose nanofibres have been known to enhance structural properties as well as the function of plastic composites. Researchers at Kyoto University in Japan have developed a wood pulp material that is cellulose nanofibre-based, and which is five times stronger yet five times lighter than steel.

Under the team’s Kyoto Process (so called because the study was initiated at the Kyoto University), chemically treated wood fibres are mixed with plastics; the wood pulp fibres are broken down into several hundredths of micronsized pieces to produce cellulose nanofibres.

The university, working with Japanese automotive parts suppliers Denso and DaikyoNishikawa, is developing a prototype car using the cellulose nanofibre-based parts, which they expect to complete by 2020.

wood-pulp

Professor Hiroyuki Yano, who led the research, said that the cost of manufacturing new materials is relatively high compared to traditional materials like steel. Yet, as far as the automotive and aerospace applications are concerned, cellulose nanofibres are low-cost yet deliver high performance, he said. For example, to produce a kg of cellulose nanofibre it costs around 1,000 yen (or US$9); compared to steel or aluminium, which cost about US$2/kg. The research also aims to bring down the cost of cellulose nanofibre by half to make mass production of the wood pulp economically viable.

Elsewhere, in the US, a group of researchers from the Washington State University (WSU) are utilising lignin to produce a strong type of carbon fibre. Lignin is a natural polymer found in cell walls of plants and trees to make them rigid.

The work, funded by the National Science Foundation Centre for Bioplastics and Biomaterials, Ford and Hyundai Motor, was presented at the 254th National Meeting & Exposition of the American Chemical Society (ACS) held in August.

Dr Birgitte Ahring, who headed the study, said that leftover lignin from biofineries end up as wastes and with little to no value. “We want to use a low-value product to create a high-value product, which will make biorefineries sustainable,” she said.

Carbon fibre with lignin is a more sustainable and cheaper alternative to the current carbon fibres made from non-renewable polyarylonitrile (PAN).

Carbon-fibre

Dr Jinxue Jiang, also of the Ahring laboratory at WSU, said that PAN is expensive and contributes to about half of the total cost of making carbon fibre. Whereas, reinforcing biorefinery lignin carbon fibre with PAN may slash the cost.

Moreover, he said that the combination of PAN and lignin is found to be strong enough for applications in the automotive industry.

For the study, the team combined lignin with PAN in different amounts, from 0 to 50%; and using a process called melt spinning, the polymer blend is made into a single fibre. The resulting carbon fibre contains about 20-30% lignin, and can be used for internal parts, castings and tyre frames of automobiles; and potentially for non-structural parts of aircraft. The new carbon fibre is yet to be tested in real-world automotive settings, the team reported.

In the years to come, the industry expects to see more new materials to emerge and gradually take over a significant portion of a car’s design. Making this possible is the increasing investment of industry stakeholders in R&D for stronger and more durable, and cheaper plastics to keep cars light and fuel efficient.

(IMA)


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