Whether it is transparent packaging from PVC or cling wrap from LDPE, the zeitgeist of today’s culture has become centred on environmental sustainability and our impact.
A major contributor towards diminishing mankind’s waste comes from recycling protocols around plastic, two of which we will be discussing today – chemical recycling and mechanical recycling:
Chemical Recycling of PVC
To have a clear understanding behind the chemical processes involved, it is important we deconstruct the fundamentals of the basic chemical composition behind PVC.
Polymers – made up from poly-(many) and –mer (part). This definition provides the basic framework behind how PVC is formed from the chemical bonding of mono-(one) mers (parts) in a repeated fashion i.e. polymerisation.
So what are the concepts behind chemical recycling? It can be defined as the act of chemical degradation of a polymer into monomers and its other basic constituents. Subsequent to this, the salvaged components can then be reused (i.e. recycled) for polymerisation into new plastic products, for example transparent packaging.
There exist many exciting developments in the scientific field for chemical recycling, such as initiatives looking into the feasibility behind solvent-based recycling of PVC through dissolution-precipitation (Sherwood, 2019).
As of now, chemical recycling is limited in scalability and new on the scene compared to its mechanical counterpart; a report by Villanueva and Eder (2014) published by the Publications Office of the European Union outlined that chemical recycling of plastic waste accounts for just 50,000 tonnes/year throughout the EU, compared to the >5 million tonnes/year from mechanical recycling.
Mechanical Recycling of PVC
More prevalent in scope today is mechanical recycling – a processes involving the manufacture of recyclates by way of mechanically processing plastic. This mechanical processing of waste into new products takes place throughout many stages, including:
It is important to note that thermoplastics, PVC included, are the only polymer types that can be mechanically recycled due to their capacity to be melted and re-processed into products, such as transparent packaging, through injection moulding and extrusion.
REFERENCES
Sherwood, J. (2019) ‘Closed-loop Recycling of Polymers Using Solvents’, Johnson Matthey Technology Review. doi: 10.1595/205651319X15574756736831.
Villanueva, A. and Eder, P. (2014) End-of-Waste Criteria for waste plastic for conversion, Luxemburg. doi: 10.2791/13033.
