Effects of reaction conditions on geopolymerization and its flame-resistant fiber-enhanced geopolymer composites

Compared to fiber-enhanced polymer composites, geopolymer matrix composites have higher operating temperatures and advantageous flow properties for manufacturing ceramic matrix composites. However, to obtain flame-retardant composite materials, an investigation of the reaction behavior of matrix materials suitable for forming geopolymer structures is necessary. Geopolymers that follow the hydration reaction mechanism are formed via condensation reactions during the mixing and aging step, and the formation of the geopolymer structure is determined by the reaction characteristics of these two stages. In this study, the mixing ratio of the elements was kept constant (Si/Al 6.2, K is Al) to investigate the effects of the synthetic reaction conditions such as concentration, temperature, and time of geopolymerization during mixing and aging. Spectroscopic analysis was used to confirm and compare the formation behavior of the geopolymer structure according to each reaction condition, and the matrix composed of Si–O–Al bonds and Q3 and Q4 structures showed flame retardancy at 1000–1200°C. Furthermore, it was confirmed that the geopolymerization degree can be estimated from the viscosity change, and that the geopolymerization reaction time can be reduced by controlling the reaction temperature and viscosity of the reactants.