Sharp Polymer Solutions and its Associates adhere to tried-and-tested recycling processes, using experienced, fully trained technicians. We also strive to embrace new technology and introduce leading-edge techniques to speed up and refine these processes for our customers where possible.
Stage 1: Initial preparation
Due to their inherent lightness in relation to volume, it is seldom cost-effective to transport plastics by truck unless they are first compressed. This is achieved in two main ways.
Baling – special baling machines are used to form dense, uniformly-shaped, stackable bales, secured by twine or wire, that can be palletised for easy loading by forklift or Hiab crane. Baling removes as much air as possible, reducing volume by up to 90% to vastly increase the amount of plastic that can be transported compared to un-baled loads.
Compacting – modern compactors break down certain plastics – usually expanded polystyrene - and use a heat process to form them into briquettes that can be recycled to generate revenue.
Stage 2: Main preparation
Next, plastics we receive need to be sorted and purged of labels, foil, dirt and other residues using several processes.
Sorting – the recycling industry has benefitted from huge technological advances in waste sorting processes, many of which are incorporated by Sharp Polymer Solutions to produce the purest recycled plastics possible.
Sawing – granulation and shredding equipment is size-limited, and sawing enables items like large uPVC windows, lengths of piping and other bulky construction materials to be cut down to manageable size.
Stripping – much of the plastic we recycle needs to be liberated from consumer goods, furniture, wheelie bins, vehicles, machinery and other items containing metal, wood, glass or different types of plastic. This entails a stripping down process.
Washing & drying – to prevent contamination of the end product, it is vital that plastics are washed to remove food and drink residues, grease, dust and other potential contaminants.
Stage 3: Size reduction process
Prior to the final stages of recycling, plastics must be reduced to more manageable size, so that they can be easily introduced to the final processing machines.
Shredding – the initial stage of size reduction involves powerful, hydraulic shredding machines with spinning rotors that rip the plastics into smaller pieces, usually around 60mm, ready for the next stage.
Granulation – granulator machines use cutting knives that rotate at extremely high speeds to further reduce the size of the pieces - referred to as reground or regrind. A perforated screen beneath the blades determines the size of the final, uniformly-shaped fragments, usually set at 10-12mm in diameter.
Stage 4: Blending process
There are three stages to blending, which is the process of combining smaller batches of the same type of plastic into a larger, homogenous mix. This is commonly achieved using an automated blender to produce final raw materials of the highest possible quality.
Pre-blending – it is vital that the purity of plastic regrind is established prior to the next stage, to prevent potentially expensive contamination of the end product. This is why checks made by pre-blending a sample batch are crucial to the recycling process.
Blending – Sharp Polymer Solutions’ customers have a wide range of requirements and it is at the blending stage that necessary refinements to the formula are made. The aim is to create a uniform, homogenous batch for use in plastic parts or products. Blending can be done by either quantity (volumetric) or weight (gravimetric). Typical blending applications include colouring and stabilisation.
Post-blending – our technicians are experienced in managing the recycling process, taking lots of care to ensure the final raw materials are of the required standard. However, with such a complex procedure there may be times when minute fluctuations in the compound lead to undesirable results. The post-blending stage addresses these issues and usually allows them to be rectified through further blending.
Stage 5: Compounding process
For lower grade heat-based applications, including certain types of sheet-extrusion and injection-moulding, regrind can be used directly from the granulation stage, although many of our customers require additional refinement that produces higher quality raw materials. This is achieved using automated compounding machines, whereby the plastic is passed along a barrel under heat, using an Archimedes screw system. This not only removes any residual moisture and noxious gases from the compound but also allows technicians to introduce specified additives and fillers via feeders. Finally, the melted plastic is extruded through a mesh screen to remove any remaining impurities and forced through a die-plate to produce pellets.
Materials Unsuited to the Standard Melt Process
The process outlined above is an efficient one that produces outstanding results but it is not suitable for all types of plastics, including plastic film, plastic bags, FIBCs, plastic-based textiles (e.g. polyester, nylon and rayon) or similarly thin materials. Sharp Polymer Solutions still has the capability to process these items but we use a specialised procedure to achieve this and produce pellets of consistent size and colour on a repeatable basis.
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