Produção de fibras hibridas de nylon 66 com cargas minerais via Solution Blow Spinning para reforço de matrizes cimenticias

Abstract

The improvement of post-cracking behavior and energy absorption in cementitious matrices has driven the development of small-scale fibrous reinforcements, essential for mitigating the fragility and low toughness inherent in mortars and concrete. Within this technological frontier, this work proposes the production and application of pure and hybrid nylon 66 (PA 66) fibers, containing kaolin or metakaolin, obtained by the Solution Blow Spinning (SBS) technique. Regarding process optimization, the SBS technique demonstrated technical efficiency and economic viability, where adjusted parameters allowed the production of pure nylon 66 fibers with sub-micrometer diameters (average of 162 nm) and smooth morphology. The incorporation of mineral fillers altered the solution rheology, resulting in hybrid nylon 66/kaolin and nylon 66/metakaolin fibers with larger diameters (376 nm and 1.60 µm, respectively) and a rough surface, a desirable characteristic for mechanical locking in the hydrated paste. The incorporation of mineral fillers aimed to mitigate adhesion limitations and promote better fiber-matrix interaction. The produced fibers were added replacing 1% of the mass of Portland cement CPV-ARI. In parallel, the direct addition of metakaolin (1% and 3%) was evaluated to compare the physical fibrous reinforcement with the chemical improvement of the pozzolanic additive. The characterization of the materials involved SEM, FTIR, TG, and XRD. Mechanical performance was evaluated by compression and flexural tensile strength tests at 7 and 28 days, complemented by microstructural analysis. The results showed increased strength for all formulations with fibers. Pure nylon 66 and kaolin-containing composites showed limited performance due to defects and a weak interface. Hybrid nylon 66/metakaolin composites, however, demonstrated more effective reinforcement, associated with synergy between mechanical reinforcement and pozzolanic reactivity. The exclusive addition of metakaolin promoted the greatest increase in strength, resulting in a denser matrix. Microstructural analysis confirmed that the quality of the fiber-matrix interface is crucial in stress transfer, reinforcing the potential of the SBS technique for the development of higher-performance and more durable cementitious composites.