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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]

In this paper, a functionalized layered double hydroxide (LDH-LS@Ni(OH) 2) flame retardant was designed and fabricated based on a multi-modifier system consisting of lignosulfonate (LS) and Ni(OH) 2 and used as a novel flame retardant for polypropylene (PP). In this multi-modifier system, LS as a compatibilizer and charring agent to improve compatibility and char yield, and Ni(OH) 2 was utilized to improve the graphitization of char residual, resulting in a PP/LDH-LS@Ni(OH) 2 composite with higher thermal stability. With the addition of LDH-LS@Ni(OH) 2 was only 15 wt%, the PP/LDH-LS@Ni(OH) 2 composite achieved a limiting oxygen index (LOI) of 30.8% and passed the UL-94 V-0 rating. At the same time, the peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP) were significantly reduced by 62.7%, 29.5%, and 46.2%, respectively. The flame retardant properties of LDH-LS@Ni(OH) 2 were mainly due to the catalytic charring effect of the transition metal elements and the physical barrier effect of the hydrotalcite. More specifically, as a highly efficient flame retardant, LDH-LS@Ni(OH) 2 has promising potential in reducing the fire hazards of PP composites. [Display omitted] • The dual modified LDH flame retardant was synthesized by co-precipitation method. • A novel hybrid flame retardant of S/Ni-containing (LDH-LS@Ni(OH) 2) was prepared. • PP/LDH-LS@Ni(OH) 2 (15 wt%) increased the LOI to 30.8% and passed the UL-94 V-0 rating. [ABSTRACT FROM AUTHOR]

In this paper, an interlayered/surface-modified flame retardant (LDHs@PA-MEL) was prepared via a one-pot method with phytic acid (PA), melamine (MEL), and layered double hydroxides (LDHs-C) and used as a novel flame retardant for polypropylene (PP). In LDHs@PA-MEL, PA and MEL self-assembled to form a PA-MEL supramolecular network for functionalization on the surface of LDHs-C, and phytate anions intercalated into the interlayer. The extreme dispersibility of LDHs@PA-MEL in PP is attributed to the dual modification of PA and MEL. With the addition of 20 wt%, the PP/LDHs@PA-MEL composites achieved the limiting oxygen index (LOI) of 29.6%, whereas the PP/LDHs-C composites exhibited only LOI of 24.8%. The peak heat release rate (PHRR), total heat release (THR) and total smoke production (TSP) for PP/LDHs@PA-MEL were 409 kW∙m−2, 70.3 MJ∙m−2, and 7.1 m2, respectively, which presented declines of 63.5%, 26.2% and 43.7% compared with those of Neat PP. The flame retardancy of LDHs@PA-MEL was mainly due to catalytic charring, release of non-combustible gases, and physical barrier effects. More specially, this work provides a feasible method for the preparation of high-performance PP composites. [Display omitted] • The flame retardant was synthesized by interlayered/surface dual modified LDHs. • A novel and renewable flame retardant of P/N-containing (LDHs@PA-MEL) was prepared. • One-pot method provided a feasible idea for efficient preparation of modified LDHs. • PP/LDHs@PA-MEL (20 wt%) increased the LOI to 29.6% and passed the UL-94 V-0 rating. [ABSTRACT FROM AUTHOR]

A novel fire retardant containing nitrogen and sulfur anion (triazine-sulphonate) was synthesized and then was directly intercalated into the interlayer of Mg/Al hydrotalcite (LDHs) by calcination-reconstruction manner to obtain nitrogen- and sulfur- containing flame retardant (LDH-NS) for polypropylene (PP) matrix. The microstructure and combustion properties of LDH-NS and its hybrid with PP composite (PP/LDH-NS) have been comprehensively characterized. XRD and SEM/EDS indicated that LDH-NS exhibited better dispersion than CO 3 2– intercalated LDHs (LDH-C) in the PP matrix. TGA showed that the thermal stability of PP/LDH-NS composites was enhanced. Cone calorimetry tests (CCT) illustrated that the peak heat release rate (PHRR), total heat release (THR) and total smoke release (TSR) of PP/LDH-NS composites were 255.8 kW m−2, 61.3 MJ m−2 and 205.7 m2 m−2, respectively, which exhibited declines of 69.7%, 43.1% and 75.0% compared with those of Neat PP. Furthermore, the PP/LDH-NS composites presented a limiting oxygen index (LOI) value of 28.6% and exhibited a vertical burning test (UL-94) V-1 rating at 30 wt% loading LDH-NS. All of these revealed that triazine sulfonate-modified LDHs significantly improved the fire performance of the PP matrix by increasing the char formation of PP/LDH-NS composites. Moreover, by adding the LDH-NS as filler for the PP matrix could promote the mechanical properties of PP/LDH-NS composites. The 30 wt% LDH-NS shown a significant fire retardance and thermal stability of PP matrix. Unlabelled Image • A fire retardant containing N and S anion (triazine-sulphonate) was synthesized. • Triazine-sulphonate pillared layered double hydroxides (LDH-NS) was prepared. • The 30 wt% LDH-NS shown a significant fire retardance and thermal stability of PP. • Triazine-sulphonate significantly promoted the flame retardancy of hydrotalcite to PP. [ABSTRACT FROM AUTHOR]

• An efficient and bio-based alginate pillared layered double hydroxides (SA@LDHs) was successfully prepared. • LOI value of PP/30 % SA@LDHs reached 30.9 % and samples can pass UL-94 V-0 rating. • Synergistic flame-retarding effect of alginate and layered double hydroxides was found. An efficient and bio-based alginate pillared hydrotalcite (SA@LDHs) was fabricated via calcination-reconstruction manner with sodium alginate (SA) and hydrotalcite (LDHs-C), and used as novel flame retardant for polypropylene (PP). The morphologies and combustion properties of SA@LDHs and its hybrid with PP composites (PP/SA@LDHs) had been characterized by SEM, TGA, cone calorimetry, LOI and UL-94 measurements. With 30 wt% loading, the SA@LDHs achieved a LOI value of 30.9 % and a UL-94 V-0 rating, whereas the LDHs-C exhibited only LOI value of 27.6 % and a UL-94 V-1 rating. The peak heat release rate, total heat release and total smoke production of PP/SA@LDHs were 260.8 kW m−2, 61.3 MJ m−2 and 8.2 m2, respectively, which presented declines of 69.2 %, 42.8 % and 32.2 % compared with those of Neat PP. These improvements could be attributed to the presence of the radical-trapping effect of SA, which leading to promote PP chains to participate in the carbonization process. [ABSTRACT FROM AUTHOR]

Ammonium polyphosphate (APP) is well known to have a synergistic action with phosphorus-based flame retardants in enhancing the flame retardant performance of matrix polymers, but the effect of APP and phosphorous-containing hydrotalcite on synergistic effect and degradation mechanism of polypropylene (PP) has not been thoroughly studied. In the present work, a synergistic flame retardant containing P 3 O 10 5− intercalated Mg/Al hydrotalcite modified by rare-earth coupling agent (W-LDH-P) and APP were prepared and used as compounded flame retardant (W-LDH-P/APP) for PP matrix. The W-LDH-P/APP and PP composites(PP/W-LDH-P/APP) possess a limiting oxygen index (LOI) value of 27.8% and achieves the V-0 standard of the flame retardant plastic. Additionally, the heat release rate (HRR), total heat release (THR) and total smoke release (TSR) for the PP/W-LDH-P/APP composites were decreased by 44.0%, 21% and 75% compared with PP/W-LDH-P. These results demonstrate that APP dramatically enhances the flame retardancy of the PP. The synergistic effect and degradation mechanism of APP and W-LDH-P are confirmed by SEM and TGA analysis. These analyses reveal that the APP and W-LDH-P promoted the formation of a more continuous and compact char layer during the burning process for PP matrix. Unlabelled Image • Hydrophobic hydrotalcite and ammonium polyphosphate were used as compounded flame retardant. • Flame-retardant mechanism of the compounded flame retardant for PP matrix was obtained. • The compounded flame retardant played an excellent effect on the flame retardancy of PP. [ABSTRACT FROM AUTHOR]