New polymerisation methods that allow the economical production of polylactic acid (PLA) with a higher molecular weight are opening the door for an increasingly broader range of applications for PLA, says Sulzer, a Swiss fluid engineering company with expertise in PLA and EPS polymerisation technology.
Sulzer technology is included in almost all PLA plants worldwide. While PLA can be produced via the condensation of lactic acid, Sulzer has opted for ring opening polymerisation. The company has now developed a turnkey process with partners to produce PLA from sugars via lactic acid followed by a downstream dimerisation and ring opening polymerisation process that has already been installed and is operational at six production facilities worldwide.
Long recognised as a sustainable option for food packaging and commonly employed - due to its high biocompatibility - in numerous biomedical applications, PLA has nevertheless in the past been held back by two things: its mechanical properties in production (technically its viscosity in the melt), and by the thermo-mechanical properties of the finished product.
The new processes solve both these issues. New PLA grades can now be produced that will considerable expand the polymer’s application base, says Sulzer.
“The latest grades of PLA are highly flexible and have a much wider scope of useable properties, making them ideal for all these plastics production methods,” noted Torsten Wintergerste, division president at Sulzer Chemtech.
The timing, he added, is excellent. The coronavirus pandemic has highlighted the drawbacks of the global economy.
“It’s evident that going forward nation states can’t operate on a business-as-usual basis. We need a domestic supply chain solution that is more reliant on national resources, with production facilities that are strategically located,” said Wintergerste.
“When the in-feed materials are based on corn, or other domestically farmed sugars, for example, local plants can be built to produce sustainable plastics for making both essential medical supplies and food packaging by injection moulding, 3D printing, film forming and extrusion.”
He argues that more efforts are needed to increase the use of biopolymers such as PLA in substitution of conventional fossil-based and non-biodegradable commodity polyolefins.
PLA is biodegradable under certain conditions and many PLA-based film applications meet the EN 13432 criteria for industrially compostability.
In addition, PLA is both sterilisable and enzymatically biodegradable using an appropriate metabolic pathway: two important properties for the medical and pharmaceutical sectors.