ORNL develops recyclable polymer for low-carbon composites manufacture

Oak Ridge National Laboratory (ORNL, Knoxville, Tenn., U.S.) scientists have designed a recyclable polymer for carbon fiber composites to enable circular manufacturing of parts that boost energy efficiency in automotive, wind power and aerospace applications.

“Our goal is to extend the lifecycle of these materials by making reuse possible without sacrificing performance,” Anisur Rahman, managing director, ORNL, says.

The team’s approach incorporates vitrimers, a class of plastics derived from thermosetting polymers that consist of molecular, covalent networks that can change their topology via thermally activated bond-exchange reactions. These dynamic, reversible bonds have enabled carbon fiber and polymer recycling as a result of their reprocessability. However, according to ORNL, reprocessing mechanically robust vitrimers, such as epoxy vitrimers, typically requires high temperatures and long processing times, which cause degradation and compromise efficient recyclability.

To overcome this, the team designed polyurea/epoxy (DPE) vitrimers and their carbon fiber-reinforced polymer (CFRP) counterparts with exchangeable disulfide cross-links, which reportedly prevailed over several intrinsic limitations. Compared with conventional epoxy vitrimers, the new polymer exhibited a six times faster bond rearrangement and ∼40°C lower reprocessing temperature, enabling it to maintain mechanical strength in six reprocessing cycles, a sharp contrast to previously reported polymers. Conversely, conventional vitrimers lost ∼63% of their strength. Moreover, the CFRPs prepared with the DPE vitrimers showed facile multi-cycle processability and repairability by thermoformation.

“ORNL’s carbon fiber composites enable fast processing and can be repaired or reprocessed multiple times, opening pathways to circular, low-carbon manufacturing,” ORNL’s Tomonori Saito adds.

For the complete study, see “Unraveling a path for multi-cycle recycling of tailored fiber-reinforced vitrimer composites.”