We use numerous things in our daily life which are made of plastics. Just to give an idea about the presence of plastics around us, few examples are:
- Most T-shirts contain polyester
- Packaging film used to protect different food articles are made of polyethylene
- Beverage bottles are made up of polyethylene terephthalate
- Midsole of jogging shoes is made from ethylene vinyl acetate copolymer
- Hard cases for mobile phones are made up of polycarbonate, polyurethane or polypropylene
- Hot and cold water-supply pipes in our houses are made from polypropylene random copolymer (PPR-C pipes)
- Toys of our kids are mostly made from polypropylene
In short, we are surrounded by plastics. Once an article made of plastic is of no use for us, it becomes waste plastic and, mostly, ends up in our waste bin. From there it either reaches a waste collection facility or remains around us as waste. If it does not reach a waste collection point it may end up in lakes, rivers, seas or oceans (transported by wind if not by humans).
What is a Plastic?
Plastics are polymers combined with different additives either for ease in polymer processing or to obtain certain set of properties in the final product.
Polymers are chemical compounds in which many small molecules are chemically attached together to form large molecules. Molecular weight of the polymers can vary from few thousands to few million grams per mole. Polymers are naturally occurring (e.g., proteins, cellulose, starch etc.) or man-made (e.g., polyethylene, polypropylene etc.).
‘The term ‘plastic’ usually refers to such polymers which have been mixed/modified with some other chemicals (called additives) for a certain purpose. For example, polypropylene (PP) is a polymer made from propylene. When we want to make a product from PP, it has to be mixed with some other additives like processing aids, heat stabilizers, antioxidants, plasticizers, UV stabilizers, fillers etc. depending upon the target product properties. As a result of this blending, PP will now be termed as a plastic. Properties of a plastic are very different from the parent (virgin) polymer.’
Why plastics are used so much?
Plastics are used heavily in making different products, mainly, because they are:
- Light weight
- Strong, durable
- Low cost
Due to these reasons, they have replaced metals, glass, ceramics and other materials in many different applications.
‘Just to excite you about plastics, Crane ropes made from a special grade of polyethylene (PE) weigh 80% less than the steel wires. This means that the cranes using such PE ropes have higher capacity and lesser downtime when compared with cranes using steel wire ropes.’
Remember than PE is just the right combination of Carbon and Hydrogen atoms!
What are Thermoplastics?
Thermoplastics are those plastics which can be reshaped, remolded or reused several times by heating (as indicated by the name). Such plastics can withstand several heating and cooling cycles without losing significantly their original properties e.g., mechanical strength etc. Commonly known thermoplastics include:
- Polyethylene Terephthalate (PET)
- Polystyrene (PS)
- Polyamides (PA)
- Polyethylene (PE)
- Polypropylene (PP)
- Polycarbonate (PC)
- Expanded polystyrene (EPS)
- Polyarylsulfone (PSU)
- Thermoplastic elastomers (TPE)
- Poly methyl methacrylate (PMMA)
- Polyvinyl-chloride (PVC) and many more…
What are Thermosets?
Thermosets are plastics which cannot be reshaped, remolded or reused by (re)heating. Such plastics have ‘chemically’ formed a three dimensional (3D) structure during their production/processing which does not allow them to be reused by heating. Thermosets will degrade upon heating to specific temperatures. Commonly known thermoplastics include:
- Epoxy resins
- Unsaturated polyesters
- Phenol – formaldehyde resins
- Phenolic resins
- Acrylic resins
- Melamine resin
- Urea – formaldehyde resin
How many Tonnes of Plastics are Produced?
Do all Produced Plastics End up as Waste?
To answer this question, we have to consider that the life span or service life of all plastics is not same. Some plastic products have a service life of less than a month while others have a service life of 15 years or up to 50 years. Therefore, from production until the end of their service life (i.e., before becoming waste) different plastics have different uses within individual value chains. Consequently, all plastics produced in a given year do not end up in waste in the same year. But at the end of service life, each plastic product will end up in waste.