Plastic recycling is still a relatively new and developing field of recycling. The post consumer items made from PET and HDPE resins have found reliable markets within the US and in Asia.
As with other recyclables, the infrastructure needed to recycle plastics consists of four major components:
- Collection: Plastics are collected for recycling rather than discarded after serving their initial purpose.
- Sortation/Handling: The collected plastics are sorted to enhance quality and then baled to reduce storage and shipping costs.
- Reclamation: The sorted plastics are cleaned and processed directly into end products or into flakes or pellets of consistent qualityacceptable to manufacturers.
- End-Use:Recycled pellets and flakes (or end products) are marketed.
Preparation (Pre-granulation processes)
Plastic scrap or waste comes in all manner of shapes and sizes such as plastic bottles, bottle crates, plastic pallets and car bumpers and a variety of material types. Often these plastic materials are not compatible with each other when it comes to recycling so they have to be identified and separated.
Granulation is a similar process to shredding, whereby spinning blades cut the plastic components into irregular shaped pieces (known as “reground” or “regrind”). Unlike shredding however, the use of grids in the grinding process allow us to control the approximate size of the reground, which can then be used as a feedstock for our later compounding processes.
Blending is simply the process of creating a homogenous batch of plastic and can be used at various stages of the plastic recycling process. Material may be blended on arrival at our recycling facilities to aid with testing of the plastic. Many polymer types are incompatible and therefore we need to ensure that incoming batches are not contaminated with different polymer types.
The compounding process is very similar to that employed in injection moulding machine, where plastic and additives are metered into a hopper at one end of a barrel. The material is transported along the length of the barrel via an Archimedes screw and as it does so is melted by applying heat by external heater bands, as well as the heat caused by friction (otherwise known as shear heat).