Your browser is no longer supported

For the best possible experience using our website we recommend you upgrade to a newer version or another browser.

Your browser appears to have cookies disabled. For the best experience of MRW, please enable cookies in your browser

We'll assume we have your consent to use cookies, so you won't need to log in each time you visit our site.
Learn more

Black is the new black when sorting plastics


The need to expand the debate on near-infrared (NIR) sorting of post-consumer plastics away from black packaging waste is one of the aims of an EU-funded pro­ject. UK-based technical compounder Luxus is leading the two-year project called NIRSort, which also involves Nordic polymer processing partner Polykemi and global plastics manufac­turer One51.

The commercialisation project aims to replace the carbon black pigment (see box) and others with alternative NIR-detectable pig­ments that would allow end-of-life plastics to be sorted with NIR sorting equipment. These new colourants will be tested in a wide range of applications beyond packaging, such as auto­motive plastics and consumer durables like home appliances and electronics.

The idea is that if these new pigments can be successfully used in such applications and then separated into individual polymer streams using NIR sorting equipment, manufacturers could adopt the use of the colourants to ensure that the products they put on the market can be effectively sorted and then recycled at the end of their lives. The first trials are expected to start after Christmas.

Colour Tone Masterbatch, which was acquired by Luxus in March, was involved in a previous WRAP-funded project published in 2011 that aimed to develop the materials tech­nology required to substitute the carbon black pigment commonly used in black food packag­ing with an infra-red reflection (IRR) black pigment. The project validated that IRR pig­ments could allow NIR spectroscopy to sort black plastic packaging waste, and it repro­duced as near as possible the shade and opacity of the carbon black pigment currently used in such packaging.

Since that original project, new masterbatch with the same NIR-sortable IRR pigment is being devised for numerous applications. It provides the opportunity to shape the tech­nical properties of thermoplastics used, for example, in car interior components including steering wheels, seats and instrument panels.

The carbon black issue

Carbon black is the name of a common pigment. Black plastics that are coloured with it present a problem for NIR detectors because carbon black strongly absorbs infrared radiation as well as visible light, so the NIR light is not reflected into the detectors.

This means that the items remain undetected and end up in the residual waste fraction from the sorting processes and are disposed of in landfill.

According to Luxus, black plastics represent around 30% of the waste electrical and electronic equipment (WEEE) and vehicle polymers waste streams. This material – around two million tonnes – is currently unrecyclable because it cannot be sorted effec­tively. On top of that, Luxus believes that a further million tonnes a year of coloured plastic waste is lost to UK landfill or incineration.

The NIRSort project aims to find a solution to allow this waste stream to be diverted to recycling and used again in new products.

tony gaukroger

Tony Gaukroger

Tony Gaukroger, director at Colour Tone Masterbatch, explains that the project is a first attempt to look at non-packaging polymers and coloured plastics other than black – because most coloured plastics also include carbon black, which absorbs the infrared and affects the ability to sort them using NIR technology.

“Essentially, [the project is asking] can we sort every polymer in every application and then potentially reclaim them? It is looking at plastics that haven’t been looked at and applications that haven’t been considered in this manner, and hopes to marry the two things together to create new opportunities.

“Nobody at the moment is looking at the post-use [automatic] sorting of automotive plastics or even electrical appliances.”

Gaukroger explains that the project is a nat­ural extension of the work that has been done on plastic packaging, and it is now time to broaden its scope. “From my point of view, and what I find most frustrating, is that the drive has been around black plastic in a couple of polymers, which is fine, you have got to start somewhere, but we need to expand that debate. We need to expand it into other polymer types, other colours, things other than packaging.

“If we assume it can be collected and it can be recycled, we then have the interesting con­cept that [there is currently] one set of plastic going into a recycling network which is up and running and you have other [plastic] things which are going straight to landfill. From a domestic point of view that could be something as simple as your old washing-up bowl.

“It strikes me as absolutely ludicrous that you have these two things happening when you can actually expand the kerbside collection to take all plastic items. Longer term, we should be aiming at reducing landfill, utilising a resource that we have already got and a process that we have partially in place and, hopefully, will be in place – and that is a complete change in thinking.

“The situation at the moment is you walk out the back door and you go: ‘I have this plastic bottle – that goes in the recycling’ and ‘I have this old [plastic] soap dish which is broken so I put that in the non-recyclable bin’.”

Gaukroger says that legislation in the UK such as the End of Life Vehicles and WEEE Directives are designed to drive up recycling rates. Yet the initial focus of achieving these targets has been on recovering metals rather than plastics because they are easier to separate and heavier, thus more useful in meeting weight-based targets. But to further increase recycling rates, focus will have to turn to recov­ering and recycling more of their plastic com­ponents.

As Gaukroger explains, the question of recy­clability focuses on the ability to separate out polymers, “and if we can do that, the world is our oyster”.

But he says a shift in thinking is required from the design stage of a product, so that end-of-life and recyclability is one of the parameters designers have to consider from the outset. This would mean factoring in whether materials can be effectively sorted when they become waste.

“That requires a lot of repositioning of ideas, and I don’t expect that a lot of this is going to happen overnight, by any means,” he adds.

What will the main challenges of the project be? “From a material point of view, we have to produce colour and packages that are aesthet­ically correct, and that is not quite as simple as it sounds.

“In the case of mixed plastic components, for instance on the interior of a car, the chances are that one component you are working with has to match another one. And because you are using different colourant systems, there is a potential metamerism [colour matching per­ception] issue that will have to be addressed.”

One problem is that colourants that are NIR detectable may not cover as well as carbon black, which could affect applications which have a strong colour base.

“From a colour point of view, it has got to be NIR sortable but it has also got to be aestheti­cally acceptable, and it has got to meet same the criteria as the original colour.”

anette munch elmer

Anette munch Elmer

Anette Munch Elmer, a plastics application and material specialist at Polykemi, which develops and produces tailor-made thermo­plastic compounds, explains that its role in the project will mainly be in polymer characterisation.

“We will get the materials for this new pig­ment that allow details to be NIR sorted. Then we can evaluate them: do they function as nor­mal black or coloured parts do? Then we will measure the material properties, such as chem­istry, ageing and thermal qualities, to evaluate whether, if we use this new pigment, we can expect changes in material properties.”

The first part of the project will be to make the material, then analyse it and make parts, before trying to sort it. Elmer says that Polykemi has a subsidiary called Rondo which procures recycled materials. Currently it is simpler to buy post-industrial rather than post-consumer material, due to the sorting difficulty: “But if we could also use post-con­sumer material, that would be really beneficial for a recycling company.”

The main challenges for Elmer are whether the new IRR pigment will be as effective as the commonly used carbon pigment. If it is, she foresees that the research could give the likes of automotive producers and electrical and electronics producers the opportunity to take more responsibility for their products.

Gaukroger believes now is the time to take on this mantle of responsibility: “I know it sounds harsh, but if we don’t [do it], it is no different to the mentality of unwrapping your bar of chocolate and throwing your wrapper out of the car. We need to be a little more responsible. What we are saying is, we need to address this in more detail and, if you want the plastics to be recyclable, the first issue is that we have to sort them.”

Should recycled material be cheaper?

There is a historic belief that recycled materials should be cheaper than their virgin counterparts, but should they?

Tony Gaukroger, director at Colour Tone Masterbatch, says: “If it is a recycled material that has been sorted and then put back into a specification as near as where it started its life in the first place, then surely the cost should become part of it?

“Even if it is an increased cost, then so be it – it is part and parcel of disposing of another problem.” 

Have your say

You must sign in to make a comment

Please remember that the submission of any material is governed by our Terms and Conditions and by submitting material you confirm your agreement to these Terms and Conditions. Links may be included in your comments but HTML is not permitted.