Overcoming the stigma of using recycled materials in class A automotive surface parts

Using recycled plastics for class A surfaces might raise a few eyebrows by those working in the automotive industry. The notorious variation in properties has meant that anything ‘recycled’ stays firmly under the bonnet where it is out of sight, and touch, of the consumer.

This view, however, is fast becoming outdating. Challenging this perception head-on is the Recyclite project, which involves Lincolnshire plastics recycling innovator, Luxus. It, and a number of industry partners, kicked off the project in 2015 after securing a €1.4 million investment from the EU’s Eco-Innovation initiative, part of the Entrepreneurship and Innovation Programme (EIP).

The project aims to commercialise a range of lightweight, scratch resistant high performance polypropylene (PP) compounds using up to 60% recycled content, for use on automotive interior trim. While Luxus had had success in the lab developing a range of lightweight recycled content polypropylene compounds known as Hycolene, it wants to scale production and commercialise its use as a drop-in alternative.

Helping develop the capability is injection moulders IAC, twin screw manufacturer Coperion and Jaguar Land Rover (JLR) offering end user guidance and feedback. A Land Rover Evoke was used for componentry to understand how material behaves and a number of components were moulded to assess how the parts and material behave on representative geometry.

“Primarily we’ve been involved in setting the technical criteria,” says Robert Crow, ‎materials innovation manager at JLR. “We are the end user so we’ve been setting the requirements within the project. We wanted to address any issues we’ve had with recycled materials in to applications that the customer can see and touch.

“What we found was there are benefits from a quality perspective, one of the things that enticed us in was its ability to deal with scratches a lot better than our incumbent talc-filled polypropylene. We also see lot less whitening compared to talc-filled polypropylene – the material this would effectively be competing with. And, the project delivers materials that are lighter weight than incumbent materials – so that is a big plus for us.”

The material also satisfies the rapid cycle time set out by OEM and tier 1 manufacturers as well as recently passing tests looking at the how the material will fare over the life of the vehicle. A JLR instrument panel used Hycolene and was tested for weathering including being resistant to the ultraviolet effects of the sun as well as heat cycling, with the overall goal of achieving a 10 year vehicle life. Any non-uniform colour change would have been unacceptable in the trials.

It puts the material in good stead with the current trend towards larger windscreens and windows to increase driver and passenger visibility. This has led to the weather requirements being increasingly made more stringent, as parts are generally more exposed than they once were.

“UV resistance was critical, with only minor fade allowed and no other colour tone change,” says Dr Christel Croft, technical director at Luxus. “Any occurrence of tackiness; grain loss; blistering; distortion; cracking; crazing; fibre deterioration; wrinkling; waviness; milking or spotting would have led to a rejection.”

Finding the feedstock?

The most common question when it comes to recycled plastics is, where does feedstock come from? This clearly has a huge effect on end properties and making a homogenous plastic, repeatedly, from various types and sources of plastic is going to be no mean feat. However, Luxus has a great deal of experience managing this process, and also access to recycled materials. For Hycolene, most of the feedstock comes from post industrial waste.

“The reason for the choice is that we need to satisfy a number of mechanical properties but also VOCs,” says Dr Croft. “We are only selecting the feedstocks we feel comfortable will satisfy the requirement of the automotive sector.”Making up Hycolene might see a variation in the amount of recycled material as the formula is made up to meet a certain performance, rather than specific chemical component that might be a specific amount and type of recycled content. It means there is flexibility in production, which is vital when dealing with recycled plastics, even those from a post-industrial and more upstream waste process. But it does raise questions about traceability, and how to manage that in the supply chain.

“We are limiting where we get the waste from as we have very tight requirements for the feedstock for the automotive sector,” says Dr Croft. “Luxus has more than 15 years’ experience in to the automotive sector, so we’re wise to the requirements of traceability and batch traceability.”

As part of the project, evaluation of many different types of feedstock has been made to make sure nothing detrimental happens to the final material. The difficulty is taking different feedstocks and then mixing them in a way that will match the final properties that have been set out. But, while much of the project has been quantifying the process, there is still a black art element involved in turning recycled plastic waste, in to Class-A surface finish parts.

“It is a mix of science and art,” says Dr Croft. “I don’t want to spoil the magic, but we use some kind of algorithm for our process to know what to use and how it will change the mechanical properties of the recycled material.

“We have a database with all the different feedstock and the typical properties, and we know how to mathematically calculate what the outcome will be, so we are not starting from zero – we start from a very good educated guess and combine this with experience to very quickly get to the right formulation.”

This expertise and knowledge is also something unique to its engineers and chemists that have built up an intimate knowledge of how to mix batches on the fly to produce very defined end properties. The process first involves making up what is known as a ‘mini-blend’ to make sure the recipe being used with the ingredients at hand matches the prediction of what the end properties of the batch should be.

The components can have anything from 0% to 50% recycled content. This can also influence other properties, for example, colour. To achieve a dark colour, it is easier to put more recycled material in. but light colours can be more difficult and need very light colours in the recycled feedstock.

Though the headline is the fact that a recycled plastic has the potential to be used on car interior, Hycolene is not being marketed as such. Like many bioplastics, it is trying to offer clear advantage in terms of being a high performance material, with the additional benefit that it can benefit Lifecycle Analysis or environmental performance.

“We don’t see a great deal of different between this product and the virgin material,” says Crow. “We have done a host of characterisation and we are getting very close and comparable results with incumbent materials. There are historic negatives about recycled materials that really don’t seem to apply to this product. This is where recycled materials need to go if they are to be excepted as a main stream alternative in the automotive space.”

For JLR, the project falls in-line with its broad strategic objectives to reduce its environmental footprint. However, it says that the project, and Hycolene is not earmarked for any current or future model. For Luxus, Hycolene 16818 has passed all the agreed criteria and validation work is now complete. It says it will continue to improve and push the mechanical properties and recycled content as high as possible.

Design trade-off

Historically there have been compromises when recycled polymers are used. Typically, this centres around a wider than normal variation in mechanical properties. This has meant parts have to be over engineered, for example using extra or thicker ribs, meaning excess weight is added to get consistent part performance.


Author
Justin Cunningham

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