The research was conducted by scientists at the Lawrence
Berkeley National Laboratory (Berkeley Lab), which is a part of the U.S.
Department of Energy's (DOE). The findings of the study appear in the journal
.
Conventional plastics cannot be recycled and hence, termed as
linear plastics. PDK plastic which can be reused and recycled is termed
circular plastic.
"Most plastics were never made to be
recycled," said lead author Peter Christensen, a postdoctoral
researcher at Berkeley Lab's Molecular Foundry.
"But we have
discovered a new way to assemble plastics that takes recycling into
consideration from a molecular perspective."
Accidental
Discovery of Circular PDK poly(diketoenamine) Plastic Polymer
- Just like many
discoveries, the unique properties of PDK plastic polymer were discovered
accidentally
- The team noticed
the potential of PDK-based plastics when one of the scientists was adding
various acids to glassware used to make PDK adhesives, and found that the
adhesive's composition had been altered
- Keen to determine
how the adhesive's composition had changed, the team looked at the
adhesive's molecular structure with an NMR (nuclear magnetic resonance)
spectroscopic device, and found that the adhesive polymer had been broken
down into its individual monomers
- On further
testing at the Molecular Foundry, they showed that the acid breaks down
PDK polymers into monomers, while at the same time allowing these monomers
to also be separated from chemicals added to give the plastic its strong,
stretchy and flexible properties
- The team found
that the resulting PDK monomers could be once again rebuilt into polymers,
which can then be used to make new plastic materials of a different color,
form or texture. For example, an old damaged black watchband made of PDK
plastic could be transformed into a white computer keyboard by this
recycling
- The old plastic
could also be upcycled by adding chemicals to enhance its properties and
to make a newer and better plastic material
Why is PDK
Plastic Recyclable?
In contrast to conventional plastic, the bonds of
PDK plastics are made up of reversible
bonds that enable easier breakdown and recycling on treating with acid. The
findings of the study do suggest that PDK plastic could be a game changer in
the plastic industry and might be a
potential
solution to make plastic
recyclable and save the eco-system. "We're interested in the chemistry that
redirects plastic lifecycles from linear to circular," said Helms
one of the team members.
"We see an opportunity to make a difference
for where there are no recycling options such as adhesives, phone cases, shoes,
watch straps, computer cables, and hard thermosets made by shaping hot melted
plastic material." Disadvantages
of Conventional Non-Recyclable Plastics
- Plastics are
polymers made of repeating smaller carbon containing units called monomers
- Several chemicals
are added to the basic plastic polymer to obtain desirable properties such
as toughness, flexibility, stretchability and lightness of weight
- These chemicals
remain tightly attached to the plastic monomers even after being broken
down in a recycling center
- The mixture that
goes into the recycling plant thus contains a mixture of various types of
plastic in different forms, shapes, color and sizes
- The resulting
output consists of small pieces of plastic that are melted to make a new
material, and it is not easy to predict how different the properties of
this recycled product is from the original plastic, thereby preventive
effective recycling
- Interestingly,
even the most recyclable plastic, PET - or poly(ethylene terephthalate)
can only be recycled up to 30
percent, and the remainder goes to landfills or
incinerators, where the material takes hundreds of years to decompose,
posing a major threat to the environment
Future Study
Plans & Suggestions
- PDK plastic could
replace conventional plastic in several areas
- Team plans to
develop PDK plastics with varying physical and thermal properties for
diverse applications including using in textiles, foams and 3D printing
- The team hope to
develop plant-based formulations and use sustainable resources that are
eco-friendly
- There is a need
to develop facilities with infrastructure to recycle PDK plastics
Summary
Newly developed PDK plastic can be completely
recycled and reused to make other plastic products and is a breakthrough in
protecting the earth from plastic pollution.
References : - Plastic Gets a Do-Over: Breakthrough Discovery Recycles Plastic From the Inside Out - (https://newscenter.lbl.gov/2019/05/06/recycling-plastic-from-the-inside-out/)
Source: Medindia
Careers
