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Layered double hydroxide (LDH) is a promising flame-retardant nano-additive for polymers, however, its efficiency is highly based on its composition and dispersity. Based on this cognition, a core-shell LDH-based architecture (LDH@TA-HP) was designed using LDH sheet as core and tannic acid and phosphazene cross-linkd polymers network (TA-HP) as shell. In the flame retardant process, renewable tannic acid (TA) as a carbon source with phosphazene was combined to form an intumescent flame-retardant system, which synergizes with the "tortuous path" effect of LDH which greatly enhance the flame retardancy of PP and LDH@TA-HP composites (PP/LDH@TA-HP). With the addition of 20 wt% LDH@TA-HP, the peak heat release rate and total smoke production of the PP/LDH@TA-HP composites were decreased by 63.5% and 47.6%, respectively, in comparison with those of Neat PP. The flame retardant level reached UL-94 V-0 rating and the limiting oxygen index (LOI) value of PP/LDH@TA-HP composites reached 30.1%, which was related to the "tortuous path" effect of LDH and the formation of the intumescent char layer of TA-HP. This investigation provided a facile strategy for the design of multifunctional LDH-based hybrids, expanding LDH potential applications in polymer composites. [Display omitted] • A novel core-shell LDH-based flame retardant was prepared via a facile method. • LOI value of 20 wt% PP/LDH@TA-HP reached 30.1% and passed UL-94 V-0 rating. • TA-HP obviously enhanced the interaction between LDH@TA-HP and PP matrix. [ABSTRACT FROM AUTHOR]

A novel and environmentally friendly lignin-based surfactant sodium lignosulfonate (SLS) modified layered double hydroxide (LDH) flame retardant (LDH-LS) was fabricated via co-precipitation method, and subsequently incorporated into polypropylene (PP) matrix to obtain the PP and LDH-LS composites (PP/LDH-LS) by melt blending method. The XRD, FT-IR and XPS results indicated that SLS had successfully modified LDH by adsorbing on the surface of the LDH nanosheet. The WCA and SEM results revealed that the hydrophobic property of LDH-LS had been evidently improved, and it displayed a more homogeneous dispersion than virgin LDH in the PP matrix. Furthermore, cone calorimetry tests (CCT) illustrated that the peak heat release rate (PHRR), total heat release (THR), and total smoke release (TSR) of PP/LDH-LS composites exhibited declines of 62.9%, 25.1%, and 43.3% compared with those of Neat PP, respectively. Besides, the PP/LDH-LS achieved a LOI value of 29.4% and a UL-94 V-0 rating, whereas the PP/LDH showed only a LOI value of 25.2% and a UL-94 V-2 rating at 20 wt% loading. These improvements of flame retardant properties can be attributed to that the well-dispersed LDH-LS and synergistic flame retardancy between LDH and SLS. [ABSTRACT FROM AUTHOR]