Recyclable and curved sandwich composites through bendable benzoxazine-based foaming core

Patent details


European patent filed

Application number


Priority date

11 July 2022


De-Yi Wang, Xuebao Lin


IMDEA Materials Institute

Transfer opportunity

License of technology


IMDEA Materials has developed a recyclable vitrimer-based syntactic foam with application in flat and curved lightweight sandwich composites manufactured by hot-press, for flexible interiors in sectors such as aerospace, railway, maritime, defence and construction.


One of the most important trends in the lightweight composites industry is the low-cost and low-energy consumption of out-of-autoclave processes of sandwich composites and the possibility to recycle or reuse high-value raw materials. Especially for large-scale products with complex curved shapes, it is still a big challenge to assemble rigid foaming cores before processing. Therefore, the lightweight composites industry demands novel rigid foaming cores that are shapeable, recyclable and easy to process, at the same time they comply with lightweight and mechanical requirements, and integrate other functionalities such as flame retardancy, thermal and/or sound insulation.

IMDEA Materials has developed a methodology to synthesize recyclable and bendable foaming cores to manufacture recyclable lightweight sandwich composites that can be used as interior parts in the transport and construction sectors.

The resulting recyclable lightweight sandwich compositions display improved mechanical properties, fire resistance, curved shape ability and out-of-autoclave processing.

Advantages and innovations

  • A range of formulations with different densities, mechanical and thermal properties are covered by the patent application.
  • Depending on the formulation, the composites prepared can combine densities between 120-250 g/m3, compressive strength of 0.8-2 MPa, heat resistance between 80-150 ˚C, thermal conductivity of 0.04-0.08 W/m·k., and V-0 flame retardancy level under UL-94 standard test.
  • Foams formulated present good thermal properties and they are easy to compound with CFRP panels by out-of autoclave processes.
  • Curved sandwich composites of 0.5-1mm thickness, areal density between 6-7 kg/m2, compressive strength of 2 MPa, flat tensile strength between 0.2-0.3 MPa, thermal conductivity of 0.06 W/m·K and V-0 flame retardancy level were prepared.


Knowledge & Technology Transfer Department, IMDEA Materials Institute


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