Fraunhofer team develops isocyanate-free polyurethane using CO2

Potsdam, Germany – A team at Fraunhofer IAP has developed an isocyanate-free polyurethane (NIPU) using carbon dioxide as a raw material, with the materials successfully processed into adhesives, foams and tubing.

In a recent interview published by Fraunhofer IAP, Dr Herfurth, research associate in the ‘polymer synthesis’ department, said the work was carried out under the CO2NIPU project.

CO2NIPU is short for "sustainable, safe, and innovative: Material use of CO2 for isocyanate-free polyurethanes. Tailored material properties for a wide range of applications."

The development was done in cooperation with Fraunhofer UMSICHT, ICT and IFAM, according to Herfurth.

It uses CO2 and amines derived from chemically recycled polyurethanes to create a more sustainable version of polyurethane with "customised material properties."

Fraunhofer said carbamates were first synthesised from CO2 to replace isocyanates as the building block in thermoplastic polyurethanes.

This formed a kind of "modular system" which allowed better control over material properties. The synthesis was then optimised to allow processing on a pilot-plant scale.

According to Herfurth, a key driver was the tightening of EU rules on isocyanates.

Since 2023, only trained personnel can work with substances containing more than 0.1% isocyanate and this prompted the researchers to develop a synthesis that does not use toxic isocyanates, he said.

Another motivation was to shift from fossil sources to renewable carbon, using captured CO2 and recycled polyurethane waste.

"By specifically incorporating carbon dioxide into material structures, we not only reduce climate-damaging emissions, we also actively contribute to the carbon cycle economy," he added.

Fraunhofer’s life cycle and toxicity assessments indicate that the NIPUs are more sustainable and "can be certified as biocompatible."

Industrial-scale production, according to Herfurth, is feasible as the synthesis method is similar to traditional PET polycondensation, and the new NIPUs are compatible with current processing lines.

"One significant milestone was when we realised that our isocyanate-free polyurethane materials are just as versatile as conventional polyurethanes," he noted.

The team has also developed reactive versions of NIPUs for coatings, foams and adhesives.

"This is very valuable because it will enable us to replace conventional thermoplastic polyurethanes in many areas... and open up completely new applications, such as resorbable NIPU fibres for medical use."

Looking ahead, the researchers see potential in multiple sectors, as NIPUs are energy-efficient to process and offer advantages in temperature-sensitive applications.

In medical devices, their “high batch consistency and low cross-linking” could improve outcomes in flexible implants and biocompatible tubing.

In automotive and packaging sectors, NIPUs may also support the shift to recyclable, lightweight and high-performance materials.