NUTEC Plastics: With Irradiation Towards a Circular Economy
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Plastic pollution is one of the most pressing global environmental challenges. By 2025 the ocean will contain one tonne of plastic for every three tonnes of fish, and by 2050, there may be more plastic in the ocean than fish. Landfills are often brimming with plastic waste and pose an environmental threat to rivers, groundwater and the ocean.
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Here is how nuclear technology can help to turn waste into valuable raw material.
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Text and Photos: Miklos Gaspar (IAEA)
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The recycling operations in Davao City, in the southern Philippines, currently use no irradiation, and can produce products with less stringent technical requirements, such as these school chairs. Irradiation can increase the thermomechanical properties of recycled mixed plastic, enabling a wider and higher-value reuse.
Mixed plastic – typically the result of household waste such as single-use packaging material – is hard to recycle and reuse because its component parts, the various kinds of plastics, have different properties. When recycling mixed plastic, the first step is to clean and shred them to small pieces.
Shredded plastic waste is then mixed at different proportions of soft and hard plastics along with aluminium-based packaging to control the density and property of the final product.
The mix is then fed into an extruder, to be melted and homogenized at 150 to 200 degrees Celsius. This temperature is high enough to melt the plastic but not high enough to degrade the material, therefore limiting the release of toxic gases.
Workers remove the melted mixed plastic, which is then moved into presser forms to solidify into the desired shape.
These are the seats of the school desks – to be assembled, painted, and sent to schools.
If the recycled plastic had better thermomechanical properties, it could have more uses. This would create a demand for more recycled plastic while at the same time reducing the demand for virgin plastics. Enter irradiation.
Plastic pellets and scraps obtained from Davao City are placed into a container for irradiation at the Philippine Nuclear Research Institute (PNRI).
The container with the plastic is placed into a small, self-shielding irradiator. (At industrial scale, bigger irradiators will be needed).
After the operator sets the parameters, the plastic pellets are irradiated to receive a predetermined optimum dose. During irradiation, the plastic polymers become more reactive, which – when the plastic is melted – will result in beneficial structural changes to the plastic polymers and also help the mixing of the different components found in the plastic waste.
By using radiation-modified natural fibres and mixing it with plastic waste in the extruder, the resulting recycled plastic is further strengthened and made sturdier. Thanks to the radiation modification, the fibres are able to mix better with the melted plastic while retaining their original stiffness and strength. They reinforce the recycled material by absorbing applied stresses from compression, bending or impact.
The irradiated plastic, mixed with the modified fibre, is placed into an extruder.
After melting, the homogenized plastic drops into cold water to cool down.
The plastic is then fed into a machine at the end of the extruder, which cuts it into small pieces.
These plastic pellets are now ready for a wide variety of uses, including even high value products such as construction materials.
Once this technology is adapted at an industrial scale, it will help keep the Philippines’ oceans and beaches cleaner.
And we will continue to enjoy sunset at Manila Bay for decades to come, without any plastic pollution swimming up against the shore!
