Plastics & Polymer Recycling Flashcards
What are the applications of plastics?
- Packaging
- Building, construction
- Electrical and electronics
- Transport (automotive)
- Furniture & houseware
- Other
What types of plastics are there?
- Thermoplastics: linear and branched polymers
- Softening when heated
- 80 % of total plastics production
- Hundreds of types, e.g. polyethylene, PET, polypropylene, polystyrene
- Thermosetting: cross-linked polymers
- Hardening when heated
- 20 % of total plastics
- Can’t be remelted or remoulded
- Difficult to recycle
What are the recovery options for EoL plastics?
- Mechanical recycling
- High-value added mech. recycling
- Low-value added mech. recycling - downcycling
- Feedstock recycling
- Energy recovery
- Disposal (landfill)
Compare the different recycling options for plastics
High-value added mechanical recycling: Limited to ~6 return cycles, b/c of degradation caused by ageing, due to UV light, heat, etc. => Closed-loop recycling not attainable, a bleedstream is needed to reject degraded material
Low-value added mechanical recycling
Feedstock recycling: Some products contain different materials bonded together, which cannot be easily separated. To recycle the, they are first chemically broken down into their basic compounds. These can thereafter be used as the raw materials for the production of new polymers, or in other processes.
What are the sources of plastic waste?
- Post-industrial waste
- Packaging
- Production
- Post-consumer waste
- Packaging waste
- ASR
- EEE
- Plastic residue from secondary paper mills
- Demolition waste
What are the driving forces for recycling of plastics?
- A lot of plastic waste, doesn’t break down naturally
- Relatively cheap
- Price reductions
- Legal requirements
- Etc.
Can all types of plastics be recycled? Why/why not?
Thermoplastics can be melted into new plastics. Thermosets can’t be melted, strengthens when heated, but can be used as a filler in new polymers, or for decomposition (energy recovery). There are also compostable films, bioplastics. Multilayer films can’t be recycled yet.
What are the differences b/w mechanical recycling, feedstock recycling, and energy recovery for plastics?
- Mechanical recycling: the product is shredded, melted and then reused.
- Feedstock recycling is a way of recycling plastics by using chemical solutions, and with this create clear polymers which can be reused again in production.
- Energy recovery is a way of recovering energy from the plastics which can’t be recycled in any way.
What are the main processing steps in plastics recycling?
Collection -> Sorting -> Processing to flakes or agglomerate (using washing lines at reclaimer) -> Processing to regranulate (by extrusion/compounding). Thermoplastics could thereafter be remelted and reformed, but not thermosets.
What are the separation technologies for plastics recycling?
- NIR
- Windsifter
- Handsorting
- Sink-float separation
- X-ray
- Drum separator/screen
- Induction separator
- Eddy current
What are the challenges in plastics recycling?
- Effective recycling of mixed plastics
- Flexible packaging is harder to recycle
- Use of dyes, fillers and other additives
- The polymer is generally to viscous to economically remove fillers
- Polymer would be damaged by many of the processes that could cheaply remove the added dyes
What are the main differences in metals recycling and plastics recycling?
All metals can be melted, in opposite to plastics, which usually also need a more difficult process to be reused. Plastics also degrade over time, while metals can be recycled over and over again
What are the options of energy recovery for waste plastics?
Heat and power recovery plants (CHP plants) use waste plastics together with other high calorific input materials. This can generate a valuable source of heat and power.
How could plastics recycling contribute to a reduction of CO2 emissions?
The CO2 emissions generated when producing plastics from crude oil is 5-6 times higher than that associated w/ recycling of the same amount of plastic. These CO2 savings from recycling only exists when the recycled plastic is used in high-value added applications, i.e. replaces the use of virgin plastics.
