How is Plastic Recycled?

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Plastic has been a hot topic lately in the UK, with the introduction of the 5p charge for plastic bags, imposed by the government to reduce plastic waste. A recent study predicted that 9.1 million metric tonnes of plastic waste would end up in our oceans by 2015, and because plastic is generally not biodegradable, it will cause great harm to marine life. As a plastic reprocessor, Plasgran naturally supports and encourages recycling.

Most plastics are recycled separately, as illustrated in the Plasgran guide to plastic recycling grades, and there are several stages to the recycling process:

Stage 1: Sorting

When plastic items are taken to a recycling facility, they are first sorted according to plastic type. This is crucial because contamination can render a batch of materials unsuitable for reprocessing. Sorting is done manually or with machines using technology that recognises different sorts of plastic.

Sorting machines are used to identify and separate large amounts of plastic. Advanced sorting machines come with infrared, x-ray or other cutting-edge sensors that can recognise a polymer’s unique signature. These machines also have ejectors that can handle incredible rates of input. Colour detection is possible with some sensors that are able to sort specific colours apart from others.

The most regularly recycled plastics include PET (polyethylene terephthalate), HDPE (high-density polyethylene), PP (polypropylene) and PVC (polyvinyl chloride). Some facilities can only process certain kinds of plastic products, but Plasgran can recycle most.

Plasgran’s custom-built facility in Cambridgeshire can reprocess just about any kind of plastic, whether single polymer, mixed or contaminated.

Stage 2: Resizing

The next step is the size reduction of the plastic waste into smaller sizes for further processing and easier handling. Standard size reduction of plastics is performed by shredders and granulators. These machines have industrial blades that perform rotational cutting to chop down the plastic, which is passed through a screen and then taken away for the next stage in the process.

Size reduction equipment.

Some recyclers end their reprocessing at this stage, and supply ‘shreds’ or ‘regrinds’ to the industry. To maintain high standards of purity and quality, all Plasgran shredders and granulators have trained operators at each machine, and metal detectors fitted to customised conveyor systems.


Stage 3: Wet separation

Next come the separation phases. After sorting and cutting, the plastic pieces can be washed to remove traces of dirt and contaminants, which vary from paper and glue, to sand and grit, and mixed plastic types that can be separated in water.

Float tanks are commonly used to separate the plastic pieces according to density. Washers and water baths or tanks are used to remove contaminants in washing lines that continuously spray hot water over the plastic pieces to remove dirt and any labels stuck to the surface of the materials. Chemicals, detergents, disinfectants or other products can be added to improve cleaning and separation.

Sink-float technology is used to separate contaminants.

Scrap plastic at Plasgran is processed by our washing and drying plants, capable of cleaning large quantities of plastic waste or scrap. We use a unique three-stage density separation tank that utilises a sink-float differentiation process to separate polymers and contaminants.


Stage 4: Dry separation

With dry treatments, plastic is differentiated based on air classification, which basically means that thinner materials are filtered from thick ones. Apart from size and shape, plastic can also be separated by other features. Heat can be applied to plastic to separate materials by melting point, whilst fluorescent or ultraviolet light helps to divide them according to colour, or their ability to absorb light.

Optical colour sorting machines can separate plastic by colour.

At Plasgran, we have a purpose-built, on-site separation plant. Using the most advanced technologies, our fully-automated machines are capable of sorting plastic materials by colour and type. We can also handle removal of metal contamination, electro-static removal of wood, rubber or foil contaminants, de-dusting and sieving of soiled or dirty materials, and removal of fines.


Stage 5: Compounding

An extruder is used to pelletise plastic regrinds into pellets.

The final step in most plastics recycling processes is compounding, which involves converting plastic regrinds into pellets, and often the incorporation of elements to transform the reclaimed plastics into high-quality, reusable materials. In pellet form, plastic is more easily distributed and remanufactured.

Machines commonly called compounding line or extruders with single or double screws are normally used to pelletise the plastics. Plasgran’s compounding service offers a viable, environmental-friendly alternative to virgin plastics. Raw materials produced from a sustainable source, such as recycled plastics, are also more cost-effective.

Through advanced technology, plus our expertise and adherence to strict industry standards, Plasgran is able to provide plastic compounds of the highest quality. We can match your precise requirements for a wide range of plastic polymers, including HDPE (high-density polyethylene), LDPE (low-density polyethylene), PP (polypropylene), PS (Polystyrene), HIPS (high impact polystyrene), ABS (acrylonitrile butadiene styrene), and much more.

To find out more about our plastic recycling services, please visit or call 01354 740005 to speak to our friendly team.

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