Are environmental concerns helping the plastics industry find new applications?

As the plastics industry sets its sights on increasingly replacing metal, could it be on the cusp of targeting its own applications, replacing plastic with bioplastic? Justin Cunningham investigates.

Metal replacement continued to be a trend exhibited throughout the plastics industry in 2013. At the world's largest plastics exhibition, held every three years in Dusseldorf, K 2013 highlighted just how far plastics have come in terms of competing with metals.

Examples of successful metal replacement projects were numerous with applications often pushing the boundaries of possibility. Where hot conditions or structural parts might once have made metal the obvious choice, increasingly plastic materials are able to offer a competitive edge.

"We actually like the trend toward turbocharging," says Peter Browning, automotive market director at Solvay Engineering Plastics. "It's going to increase the temperature of engines and drive a need for higher performance materials, capable of operating at higher temperatures. For us, we can respond to that nicely."

Solvay supplies polyamide and Nylon 66 materials to the UK and Europe for automotive powertrain applications, as well as the electronics market. It has a history of developing materials for hotter applications and recently developed Technyl B2 V15 to specifically respond to the increasing heat demand from turbocharged engines, comfortably operating at a continuous 210°C.

"We are still essentially selling a trade off," says Browning. "Plastic is simple, you can add in functions, and it can simplify production. But its operational temperature range is always going to be less than metal."

Despite the automotive industry being keen to lightweight, Solvay has had to work hard to break the routine of designing in metal by showing engineers how to unlock and extract more economic value from plastics. While the looming tailpipe emission targets of 2020 are forcing the hands of OEMs to at least consider other material options, scepticism about performance for the uninitiated is common.

Getting past plastic reservations
"When we are moving customers away from metal, we need quite a compelling argument as there tends to be less confidence in plastic as a performance material," says Browning. "If you're a designer of engine support mounts and your company has been doing that in metal for the last 50 years, there is obviously a lot of data, confidence and experience to call on. For plastics, it can feel like you are entering the unknown."

As a result Solvay has developed a dynamic simulation tool it calls MMI (multi-scale modelling, mechanical calculation, and injection moulding simulation), an anisotropic simulation program that aims to build confidence, reduce risk and allow engineers to sleep at night. While historically it has been very difficult to model, for example the impact of different orientations of reinforcing fibres, MMI is surprisingly accurate at modelling the many different variables that come in to play when using performance plastics.

While the push for lightweight solutions is helping the plastics industry deal with environmental issues indirectly, there is a desire for more direct action. Rightly or wrongly the plastics industry does not have the best reputation when it comes to environmental issues and certainly in Europe, it is keen to address its shortcomings.

"The chemical industry has had its image challenges and a key part of confronting those issues is ensuring what we do is sustainable, reliable and environmentally friendly," says Browning. "We have a specific example where we have used castor oil to derive a salt resistant Nylon product used for radiator tanks in extreme weather climates like South Korea, Russia and northern Japan. They are big users of calcium chloride on the roads and this material blended with normal Nylon actually provides superior resistance to these aggressive conditions.

"Yes, we see a 'bio' driver here and customers are interested in that. However, they're more interested in 'bio' associated with performance and not 'bio' as an end in itself. So while it is a good additional claim, the underlying driver is performance."

Plastics giant Dupont is also keen to bring innovative solutions to market that tackle both the concerns and challenges facing engineers. It too has seen a strong market push toward metal replacement parts and applications, with much more mechanically demanding structural parts now beginning targeted.

The company is continuing to develop its thermoplastic composite (TPC) for the automotive industry, which aims to fulfil both the strength and processing requirements for high volume automotive manufacture. In collaboration with Citroën, it has developed a process using its Zytel Nylon 66 effectively as a resin system to infuse continuous glass fibres (that can be woven or unidirectional) to produce TPC prepreg sheets.

Perhaps one of the most impressive applications of this technology has been demonstrated with its work with Peugeot Citroën to produce a side impact beam made from the TPC. In comparison to the original beam made from ultra-high hardness steel rated at 1200MPa, the thermoplastic composite is 40% lighter and able to absorb more energy. The process is currently being further developed and optimised so parts can be mass produced in 2016.

Dupont is also active in addressing concerns around processability and the manufacturing impact of changing materials, from metal to a TPC. As a result it has been developing the material so it can be formed using almost identical tooling, machines and processes as a metal part.

The side impact beam is produced from a sheet of thermoplastic continuous glass fibre composite that has been cut to shape before being heated and stamp formed in to the 3D beam. The part is then overmoulded (orange/red) with short glass fibre PA66. This consolidates stiffness and strength and uses clever geometry in its reinforcing ribs to maximise performance and minimise weight.

Dupont calls its TPC material, Vizilon, and is producing it in semi-finished prepreg sheet forms that will be supplied to the automotive industry in much the same way as sheet metal, which can be stamped or formed as required.

Patrick Cazuc, automotive director Europe for EMEA at DuPont Performance Polymers, says: "This technology can be well suited for crash components, opening up a whole new field of plastic adoption in cars."

Plastic replacement next?
Like Solvay, Dupont is keen on addressing the issue of sustainability and improving the green credentials of plastic materials. Its overall corporate strategy and direction for this is to reduce dependency on petrochemicals to a point where there is no dependency at all.

"This is the long term journey we are on and it will no doubt evolve over time," says Thomas Werner, business development manager for renewably sourced materials at Dupont Performance Polymers. "We need to differentiate between first generation products, second generation products, and then subsequent generations after that. The goal is to develop natural, non-food competing, plastic raw materials.

"Using a starch to make Polylactic Acid (PLA) is far simpler than if you try to create polyether glycol from a non-food bio-source. But we are on the way to actually doing that and we have one product, Hyrel RS, that contains between 20% and 60% renewably sourced polyether glycol derived from biomass. This is replacing petrochemical based polyether glycol in the soft (amorphous) segments of standard Hytrel."

Having a high bio-content in any material is a good indicator that its carbon footprint is likely to be lower than a material derived from fossil fuel, as CO2 would likely be absorbed during the living part of any naturally derived bio-based raw material; be it algae or some kind of plant.

The interesting part of bio-blended materials is that they display 'different shades' of properties, which can put a different spin on the properties of products and their potential applications.
"We developed a material for Toyota used for its air conditioning system and interior," says Werner. "Here, surface appearance and durability of the bio-based material was actually better compared to the petrochemical based one. And this is what we want to do: take the bio-based materials and find developed products where we can add functionality.

"For the bio-based plastics we are being asked for its footprint as much as we are asked about its physical properties. That has changed quite a lot in the last three years or so. In the beginning, we had to explain the material, and there was some suspicion that bio-based products were not as good. However, we are winning that argument and winning over customers. Increasingly they see it is not just viable and equivalent, but can deliver more of an advantage depending on which properties you look at."

For example, a head and neck support (HANS) for racing drivers, from HANS Performance Products (HPP), uses the renewably sourced DuPont Zytel RS reinforced polyamide to deliver the required impact resistance. The renewably sourced (RS) material actually reduces the parts weight by 30% weight while offering better chemical and moisture resistance versus the standard PA66. The aim is to make the material attractive not just as an 'eco-conscious' choice but for performance benefit.

"If you compare Hytrel RS with the standard PA66, it is the better product," says Werner.

It is a message that was heard across the K Show and continues to resonate across the plastics industry at large. Firstly, applications are being identified where replacement of metallic materials with plastics offers distinct performance and economic advantage. However, the next step of this journey is beginning to emerge with increasing identification of oil based plastics applications that could be replaced by bio-based alternatives.

It must be stated that it is early days for these materials but the trend is likely to continue to feature on evermore parts and products through this decade and in to the 2020s. As bio-based plastics continue to be refined, so too will identification of applications where they can offer superior performance over oil based alternatives.

"That seems to be the way it is working; first we lightweight by replacing metal, then we look to substitute plastic with bioplastic," concludes Weiner.

Justin Cunningham

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