Thermoset polymers with permanently cross-linked networks have outstanding mechanical properties and solvent resistance, but they cannot be reprocessed or recycled. On the other hand, vitrimers with covalent adaptable networks can be recycled. Here we provide a simple and practical method coined as "vitrimerization" to convert the permanent cross-linked thermosets into vitrimer polymers without depolymerization. The vitrimerized thermosets exhibit comparable mechanical properties and solvent resistance with the original ones. This method allows recycling and reusing the unrecyclable thermoset polymers with minimum loss in mechanical properties and enables closed-loop recycling of thermosets with the least environmental impact.

The effects of particle size and silane treatment on the impact strength are experimentally evaluated for epoxy reinforced with nanometer- and micrometer-sized SiC particles. These nano and microcomposites are fabricated using two different sizes of SiC particles: 60–100 nm and 2–4 mm in diameter. The weight fraction of particles is fixed at 1.5% and the particles are dispersed using ultrasonication. For the purpose of investigating the effect of particle–matrix adhesion on the failure process, composites are fabricated using both as received and silane treated SiC particles and γ-aminopropyltriethoxysilane is used as an organofunctional coupling agent to control adhesion properties. Impact energy is measured using Frank IZod impact pendulum instrument. Additionally, fractured surfaces are observed under a scanning electron microscope to investigate particle bonding, particle dispersion, and toughening mechanism. Particle size along with dispersion and bonding are observed to affect the impact strength. It is observed that both the improved particle dispersion and bonding due to silane treatment lead to an increase in impact strength. With regards to particle size, the composites with nanometer-sized SiC particles are having greater impact strength compared to micrometer-sized particles.

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