Effect of modified hydrotalcites on flame retardancy and physical properties of paper

Functionalized layered double hydroxides (LDHs) based on a multi-modifier system composed of itaconic acid (ITA) and titanate coupling agent (NDZ-201) were designed and fabricated in this paper with the aim to develop high-performance fire retardant paper. The structure of LDHs were characterized using Fourier transform infrared spectroscopic analysis, X-ray diffraction analysis, thermogravimetric analysis (TGA), scanning electron microscopic analysis, cone calorimetry, and laser particle size analysis. The results showed that carbonate anions were partially replaced by ITA, whereas the titanate coupling agent was attached to the surfaces of the hydrotalcites. The limiting oxygen index (LOI), TGA curves, total heat release rate (THR), and heat release rate (HRR) indicated that as the addition of hydrotalcites increased, the modified LDHs’ LOI value and thermal stability noticeably increased compared to the unmodified hydrotalcites, and the HRR and THR of the material decreased. When the addition amount was 25%, the LOI of ITA-LDHs was 26.9%. However, the Mg-Al hydrotalcites adversely affected the strength index of flame-retardant paper; the modified hydrotalcites clearly reduced this effect, and the whiteness of paper increased and reached 83%.