Should engineers be nervous when specifying recycled materials?

As raw materials get more expensive and scarce, why not take materials in the existing supply chain, all be it at the end of their life, and use those instead? It's a nice idea as it cuts down on the amount of material that has to be sent to landfill and can make the lifecycle of materials much more sustainable and economical.

There seems to be increasing angst in industry about material volatility both in terms of cost and supply. While the list is relatively short at the moment, all are well aware that it is only a matter of time before more are added to the list. With this in mind, one way to shore up against material scarcity is to take existing refined materials and reuse them instead? It's a nice idea as it cuts down on the amount of material that has to be sent to landfill, and can make the lifecycle of materials much more sustainable and economical.

The metals sector has been able to do this very effectively, with supply chains, quality and processes well established to the extent that some 90% of steel in the UK is reused or reprocessed. Perhaps key, is that metal properties do not tend to downgrade and recycled metallic's are substantially cheaper and produce less CO2 than smelting plants processing virgin ores.

Plastic, however, is yet to be accepted in quite the same way. The concern is that the properties of recycled plastics deteriorate and fall well short of virgin materials, both in terms of mechanical strength and surface finish. And given the nature of recycled plastics, they tend to make engineers nervous as different batches can yield different results, and it's this question of variability that puts many off.

However, battling to change this perception is ­­Luxus, based in Louth, Lincolnshire. It has seen its business grow significantly in recent years as it's been able to systematically improve the quality of recycled plastic materials.

It has already had success in the automotive industry for under bonnet parts, and impressively has also had success in interior parts, boasting an ability to produce the first class finish specified by carmakers.

Luxus is now seeking increasing applications from automotive and industrial sectors as it begins to convince the masses that it's recycled plastics are up to the challenge.

"There has been caution in using and specifying recycled plastics," says Terry Burton, technical manager at Luxus. "But there is now much greater pressure on companies to use recycled based material, and that's helped take away some of that initial caution. It's led to a sea change in the industry as people have realised it doesn't result in a dramatic change in properties."

Luxus began supplying the automotive sector with recycled plastic materials in the early 1990s with the production of splash guards. And from there it has been able to make inroads for applications including under-bonnet and under-body parts. It now has repeatable processes in place that are able to provide the quality needed for interior parts, where surface finish is vital.

"This was a big step and it meant we could start looking at waste in a different way," says Burton. "The best waste material goes to our interiors for 'A' surface finish in the automotive industry, but we're still able to use other grades for applications where those properties are less important."

This led to Luxus developing methods of sorting the waste as it comes on site. At the moment, the most effective way of achieving good results is still reliant on people, trained to assess the different types of plastic based on looks, touch and experience.

Same cake, different recipe
Luxus is able to do something few plastic recyclers have managed, in the way it blends its waste plastics together to yield a set of properties. And this is its goal, the end set of properties. It effectively compounds its plastics on a continuous basis depending on the waste that comes in, but always to achieve the same set of properties from the end material.

"We have always done something that other recyclers don't in terms of blending materials ready for production," says Burton. "That gives us a homogenous mix of the materials. We know the colour, we know the mechanical properties, we know the flow properties, and we can see if there is any contamination. We know at the end we have an even mix of predictable performing material.

"So we can formulate, and create formulations, based on homogenous mixes of material to create technical grades of plastics. We can create grades that go from automotive interiors to under bonnet applications in to building services and down to things like wheelie bins and finally plant pots and coat hangers."

One dichotomy that has emerged is that engineers tend to specify recycled plastics much more highly than a virgin plastic. Normally, a plastic supplier provides a 'spec-sheet' that is accepted, but because Luxus has recycled content, engineers tend to be more cautious, especially for automotive applications where internal finish gives a huge impression of overall car quality. And the fact that the 'ingredients' making the batches of recycled plastics can come from many different places means that Luxus must carry out much more testing, to both satisfy its own quality standards, and prove as much to customers.

Luxus also supplies virgin plastic materials and can produce compounds that vary from 100% virgin plastic to a 95% recycled plastic material (masterbatch and additives make up the remaining 5% of a formulation). To give an idea, under bonnet plastic parts are typically 95% recycled while car interior parts are usually made up of some mix of virgin and recycled materials.

"It's that ability to give people options that they like," says Burton. "We do technical and complex formulations where we can manipulate the properties. Of course, the recycling process does affect the possible monomer chain length because of the heat process, and that reduces strength slightly against a virgin plastic. But then we can add process stabilisers to help minimise that. We're taking a whole host of recycled materials and achieving a specification, rather than returning those materials to what they were at the beginning of their life."

There is no doubt that the use of recycled plastic is going to proliferate throughout industry in coming years. But, it is unclear whether process improvement will lead to it becoming as common place as recycled metals. One thing for certain is the myths and reservations currently surrounding recycled plastics, are soon to be put firmly in the rubbish.

Author
Justin Cunningham

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