Analysis: plastic waste is a huge problem and there is a growing interest in how to create high value materials from recycled plastic

Ireland is the EU’s biggest plastic waste producer. But plastics combined with the same material fibres make composites and these are key to winning the fight against global warming since they are strong, lightweight and durable so their use in cars is rapidly growing.

The Irish Composites Centre has developed technology to convert waste "single-use" plastic bottles into value-added composites that are themselves fully recyclable materials. This means that Ireland can lead the fight against plastic pollution of the planet instead of being part of the problem.

There are many different types of plastic and they are important materials in the modern economy. However, if plastic materials are not disposed of responsibly, they can cause serious negative impacts on the environment and public health. In some plastics, there are chemicals present that can migrate into water supplies and then into our bodies. If plastics end up in the ocean, they can have a detrimental effect on sea life and ultimately, that has a detrimental effect on us.

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It is imperative that proper recycling of plastic waste is made more effective and prioritised. Recycling is the process of recovering post-consumer products and scrap or waste plastics and reprocessing the material into useful products. Unfortunately, the vast majority of waste plastic is not recycled and goes to incineration or landfill, where it remain for a very long time since most plastics are non-biodegradable. 

275 million metric tonnes of plastic waste was generated in 192 coastal countries in 2010, with 4.8 to 12.7 million metric tonnes entering the earth’s oceans. Without waste management infrastructural improvements, the cumulative quantity of plastic waste available to enter the ocean from land is predicted to increase by an order of magnitude by 2025. Therefore, recycling has to be part of a global effort to reduce the waste stream of plastic materials that are having a negative impact on the planet.

Until December 2017, the European model for dealing with plastic waste was predominantly based on incinerators (roughly 40 percent), landfills (around 30 percent) and exports (more or less 12 to 15 percent), primarily to China, Hong Kong and other countries in the far east. Growing quantities of low-grade and low-quality plastics unfit for recycling, often in the form of single use products or packaging, along with low performing separate collection schemes, have led to significant under capacities for plastic recycling in Europe. The most likely plastic to be recycled in Europe are those which were clean and high quality. For the rest, export to countries with cheaper labour costs or reduced environmental standards was the easiest option and that meant mostly China.

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Plastic packaging waste is a huge problem around the world. Despite efforts in some European countries such as plastic bottle deposit schemes or having to pay for plastic bags, the average EU citizen creates 31 kg of plastic waste per year. Eurostat figures show that the worst country by a long stretch is Ireland, where 61kg of packaging are thrown away by the average Irish person per year. This is 9kg more than the second most prolific country Luxembourg and way more than the UK where its citizens are responsible for 35kg of waste per person. Ireland’s waste level reached a crisis point following the move by China in January 2018 to close the world's biggest recycling market.

The first-ever European Strategy for Plastics in a Circular Economy was adopted in January 2018 which hopefully will transform the way plastic products are designed, used, produced and recycled in the EU. This strategy will help protect our environment, reduce marine contamination, greenhouse gas emissions and our dependence on imported fossil fuels. It will support more sustainable and safer consumption and production patterns for plastics.

Last October, the European Parliament overwhelmingly voted in favour of a directive which will ban items such as disposable plastic plates, plastic straws and cotton swabs by 2021. Under the directive submitted by the European Commission at the end of May 2018, further recycling measures will be taken across the region to ensure that 90 percent of plastic bottles are recycled by 2025.

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Such developments have stimulated interest in the development of high value materials from recycled plastic waste. Composite materials are plastics reinforced with fibres, generally carbon and glass. They are lightweight, strong and durable and, among many other things, are crucial for reducing greenhouse gas emissions from air, sea and land transportation to mitigate global warming.

The conundrum is that these composite materials themselves will become part of the waste plastic problem unless strategies are developed for recycling not only the plastic but also the reinforcing fibre. In the composites industry, the epitome of recyclability is Self-Reinforced Polymer (SRP) composites, where the reinforcing fibre is a highly oriented form of the same thermoplastic as the matrix. This combination of high tensile fibres with a tough, semi-crystalline matrix provides adequate reinforcing strength, stiffness, dynamic toughness, elongation to break and environmental resistance for many high performance applications.

Crucially, any waste/scrap and end-of-life materials can be fully recycled into, for example, injection moulding compounds, thus satisfying the demand for materials to be green. Polyesters such as polyethylene terephthalate (PET) are ideal for the Circular Economy since they can be depolymerised to the original monomers by a commercially viable process and then re-polymerised back to the polyester.

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The SRP industry as a whole has moved forward significantly in recent years with a number of companies developing commercial products for different industrial sectors such as automotive, personal protective equipment and sporting goods.

SerPET is an  Enterprise Ireland Commercialisation Fund project which has been completed in IComp where the main objective was to develop self-reinforced composites based on recycled PET from post-consumer bottles. In 2017, 20 million tonnes of PET were used globally in bottles. PET is used for a wide variety of other applications including films, fibres and packaging and presently creates the highest volume of waste plastic generated across Europe.

This project has proved extremely successful. Core-sheath type co-extruded fibres have been developed where the sheath (surrounding tubular layer) is melted and forms the matrix and the high strength fibre core remains undamaged and acts as the reinforcement. These fibres can be converted into a textile by weaving, braiding, knitting, etc. and combined with, for example, glass fibre to suit the particular application. This work has culminated in a patent application. Tri-layer tapes, which can be woven into flat sheets, have also been developed as a lower cost alternative to fibres in which the self-reinforcement is provided by very narrow high tensile ribbons.

Eurostat figures show that the worst country by a long stretch is Ireland, where 61kg of packaging are thrown away by the average Irish person per year.

Within the scope of the SerPET project, only limited quantities of fabrics were produced using these co-extruded fibres and tapes to manufacture small coupons of composite material by consolidation in a heated hydraulic press. The fibres and tapes developed in SerPET are capable of undergoing rapid processing under either conventional heating or low energy radiofrequency (RF) and microwave (MW) heating, for the manufacture of high-performance, fully recyclable thermoplastic composite parts.

The aim of this technology is to tackle the problem posed by plastic bottles by recycling them on the industrial scale into high-value self-reinforcing composites. The amount of energy necessary to transform these materials into finished parts will be considerably reduced. IComp wants to develop the product in all its forms and to disseminate this technological development and its concomitant advantages to the wider business community and to all stakeholders (including users of single-use plastic bottles) to mitigate the environmental impact of waste plastics globally. It is incumbent on scientists and engineers to tackle head-on the impending ecological disaster on the earth perpetrated by the irresponsible disposal of plastics.

The views expressed here are those of the author and do not represent or reflect the views of RTÉ