Issue 9/2021 - New process makes biodegradable plastics more easily decomposable

On April 21, the latest study in the journal Nature said that American scientists have invented a new process: using only heat and water, these compostable plastics can be more easily decomposed
.

Studies have found that enzymes wrapped in random heteropolymers (RHPs) do not change the properties of
plastics.
When exposed to heat and water, this enzyme gets rid of the polymer-wrapped material and breaks down the plastic polymer
.
Plastics can be melted at a temperature of around 170°C and extruded into fibers
like ordinary polyester plastic.

To make plastics, the team wrapped billions of nanoscale edible polyester enzymes in RHP and embedded them in
plastic resin beads.
To trigger plastic degradation, simply add water and a small amount of heat
.
Up to 98% of plastics made using this process degrade into small molecules
.
And this process avoids the creation
of microplastics.

For polylactic acid (PLA), the researchers used an enzyme called proteinase K, which chews PLA into lactic acid molecules; For polycaprolactone (PCL), lipase
is used.
Both enzymes are inexpensive and readily available
.
At room temperature, 80% of the modified PLA fibers are completely degraded
within a week.
The higher the temperature, the faster
the degradation.
Under industrial composting conditions, modified PLA degrades within 6 days at 50 °C and PCL degrades
within two days at 40 °C.