Overview
The aim of this project was the replacement of traditional mineral oil based plastics with innovative bio-based resin systems for aeronautical applications. Due to the high quality requirements of this field this challenge was much larger than in other industrial segments, therefore the use of functionalised plant oils alone as bio-components of matrices in aeronautical composites is not enough. According to our concept, flame retarded special hybrid thermosetting polymer system had to be prepared using bio-based components. Innovative combination of new ideas of resin synthesis including click chemistry and sol gel reactions (providing flexibility of organic component balanced with hardness and thermal stability of the inorganic component), patented environmentally friendly reactive flame retardant components and modification of natural fibre by (patented) organic chemical and/or enzymatic method resulted in bio-based epoxy composites of highly enhanced performance.
The knowledge of a recently patented idea was adapted to improve the recyclability of thermosetting bio-composites. The robustness of the technology was ensured by process controlled reactors equipped with unique spectrometric feedback. The team of proposers included various research groups of Budapest University of Technology and Economics (BME), whose activities (preparative green chemistry, enzymatic reactions, reactive fire retardancy, hybrid bio-composites, and innovative structural and mechanical evaluation) complete each other. The experiences of the proposers acquired in realisation of another current CleanSky project represented a good starting point for achieving the required scientific and technical quality.
Funding
Results
The development tendency of the replacement of traditional mineral oil based plastics with innovative bio-based resin systems is nowadays characteristic for many segments of the industry; however, for aeronautical applications (interiors and/or structures) the challenge is much larger than elsewhere. To meet this challenge, a flame retarded special thermosetting polymer system was planned to be prepared using bio-based components.
The project aimed at providing replacement for conventional petroleum-based plastics with new and innovative bio-based composites by development and synthesis of their components for aeronautical applications (internal and external elements as structural material). Because of extreme working conditions in aeronautical field, the quality and safety requirements were considerably high, therefore researchers face major challenges in fulfilling these requirements.
In the frame of this project a new type of epoxy bio-materials were produced that can meet the high requirements of aviation industry. During the synthesis different types of sugars were used as starting materials, which are renewable bio-materials and do not compete with the food industry due to the large oversupply of sugar in the recent decades. Innovative chemical methods were used for manufacturing resin components in order to improve the properties of the resin, including mechanical characteristics and reduced combustibility. The component synthesis process design was carried out considering the principles of green chemistry, energy efficiency, opportunities to scale up, environmental and health protection. Qualification and selection of the right combination of compounds was verified based on complex criteria including chemical, physical and mechanical properties, thermal stability and flammability. The synthesis of the chosen optimal bioresin component was planned to be up-scaled using advanced reactors, such as a computer-controlled reactor equipped with online Raman feedback and microwave heating.
In order to achieve improved mechanical strength necessary for application as a structural material, natural fibres were planned to be used. By combining bio-based resins and natural fibres the aim was to prepare fully bio-based composited meeting the requirements of the aeronautical sector as well. To reach this goal the adhesion between the matrix and the fibre had to be improved and the flammability requirements had to be reached by surface treatment elaborated during the project.
After preliminary experiments, the impregnation of the chosen natural reinforcing fabrics with the synthesized bioresin was carried out and samples for detailed evaluation were manufactured. After selecting the optimal resin/fibre systems (composition, treatment and structure) for industrial evaluation, the bio-composites prepared were subjected to extensive testing including dynamic mechanical analysis, tensile tests, three point bending tests, limiting oxygen index measurement (LOI), UL-94 and cone calorimeter tests, evolved gas analysis laser pyrolysis coupled with Fourier transformation infrared spectrometer. The most appropriate biocomposite system was planned to be tested in a form of sandwich composite using polymethacrylimide foam cores, aiming at application as internal floor panels in aircrafts.