Bisphenol F and aniline-based benzoxazine monomers were selected to fabricate basalt, glass and carbon fiber reinforced polybenzoxazine via vacuum infusion, respectively. The impacts of the type of fiber reinforcement on the resulting material properties of the fiber reinforced polymers (FRPs) were studied. FRPs exhibited a homogenous morphology with completely impregnated fibers and near-zero porosity. Carbon fiber reinforced polybenzoxazine showed the highest specific mechanical properties because of its low density and high modulus and strength. However, regarding the flammability, fire, smoke and toxicity properties, glass and basalt reinforced polybenzoxazine outperformed carbon fiber reinforced polybenzoxazine. This work offers a deeper understanding of how different types of fiber reinforcement affect polybenzoxazine-based FRPs and provides access to FRPs with inherently good fire, smoke and toxicity performance without the need for further flame retardant additives.

Different types of phosphorus containing halogen-free flame retardants (FRs) were added to an epoxy-dicyandiamide resin formulation in order to study to which extent they affect its glass transition temperature (T_g), tensile properties, thermal stability and burning behavior of the resin. For this purpose, an additive-type FR (ammonium polyphosphate encapsulated in melamine resin, MAPP) and two reactive-type FRs i) a commercial epoxy resin pre-reacted with 9,10-dihydro-oxa-10-phosphaphenanthrene-10-oxide, (DOPO), and ii) a phosphorus containing hardener (poly(m-phenylene methylphosphonate), (PMP) were used. It was observed that the addition of additive-type FR did not affect in great extent the T_g and provided a V-0 rating in UL94 test at low loadings. The addition of reactive-type FRs (DOPO and/or PMP), however, modified the structure of the chain network resulting in lower crosslink density as a consequence of their higher equivalent mass, but achieving also with low PMP content V-0 rating.

Chemical recycling of disulfide-based vitrimer carbon fiber composites offers a viable route for circular management of structural composite materials through recovery of both reinforcement fibers and matrix constituents. In this study, two vitrimer systems with different resin compositions but a common disulfide-containing hardener were evaluated to identify conditions enabling efficient network cleavage and fiber recovery. The influence of solvent and reducing agent systems was systematically assessed, leading to optimized conditions for effective matrix depolymerization while preserving carbon fiber integrity. Scale-up experiments demonstrated that the recycling process is transferable from small-scale coupons to larger laminates and continuous fiber composite architectures without loss of fiber structural performance. Recovered resin was successfully reprocessed into vitrimer-based films, demonstrating retained functionality and reprocessability. Overall, this work establishes a scalable chemical recycling strategy for carbon fiber reinforced vitrimer composites, supporting their integration into circular composite manufacturing frameworks.

In this work, we present the development of a novel thermoset epoxy network that combines highly dynamic characteristics (reprocessability, reparability, and recyclability, 3R) with enhanced surface repellency. The conventional dynamic hardener of a 3R epoxy network was partially substituted with two different polydimethylsiloxane (PDMS) compounds at varying weight percentages and molecular weights, allowing us to systematically evaluate their influence on the material’s properties. Mechanical, thermal, and dynamic characteristics were retained, confirming that the substitution does not compromise the functional integrity of the network. Importantly, the surface properties were significantly improved, demonstrating enhanced repellency without affecting the core 3R functionality. A comparative analysis of the two PDMS variants revealed the influence of chemical structure and molecular weight on surface performance, providing insights into the design of multifunctional, sustainable epoxy networks.