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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]

To overcome the flammable defects of polypropylene (PP) and expand its application in more fields, it is imperative to develop PP composites with fire retardance, smoke suppression, and mechanical strength. Here, inspired by the structure of the dandelion flowers, a core-shell CMSs@LDHs flame retardant was prepared by growing LDHs nanoflakes on the surface of CMSs to combine the excellent flame retardancy of CMSs with the advanced smoke suppression of LDHs, and then it was applied into PP matrix through melt blending to satisfy the fire safety requirements of PP. With the addition of 20 wt% CMSs@LDHs, the PP/CMSs@LDHs composite passed the vertical combustion tests (UL-94) V-0 rating, and its limiting oxygen index (LOI) value of it also reached 28.9 %. The peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP) of the PP/CMSs@LDHs were also decreased by 46.5 %, 30.8 %, and 11.9 %, respectively, compared with those of the Neat PP. [Display omitted] • The synthetic raw materials of CMSs are renewable. • The core-shell structure was synthesized based on the flower structure of dandelion. • CMSs act as the carrier of LDHs and promote the dispersion of LDHs. • LOI of PP/CMSs@LDHs (20 wt%) reached 28.9 % and samples can pass 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]

[Display omitted] • Novel hierarchical CMSs@LDH@PZN nanospheres with double shells are synthesized. • CMSs@LDH@PZN has well compatible and outstanding thermostability in PP. • CMSs@LDH@PZN enhances the flame retardancy and toxic smoke suppression of PP. Developing advanced performance polypropylene (PP) composites with less smoke, eco-friendly and efficient flame retardants (FRs) has been a growing focus of research. In particular, it was significant to reduce the emissions of smoke and toxic gases generated during the burning of PP so that it meets green and safe industrial requirements. In this work, a CMSs@LDH@PZN hierarchical core–shell framework was designed and synthesized by using carbon microspheres (CMSs) and layered double hydroxides (LDHs) nanosheets connected to CMSs by electrostatic forces with polyphosphazene (PZN). The structure, composition and morphology of CMSs@LDH@PZN were characterized by SEM, TEM, FT-IR, XRD and TG, and the results were shown the triumphant preparation of the well-designed hierarchical core–shell structure CMSs@LDH@PZN. Additionally, the total smoke production, peak heat release rate and total heat release rate of PP/CMSs@LDH@PZN composites were decreased by 56.2%, 41% and 43.4%, respectively. With the addition of 20 wt% CMSs@LDH@PZN alone, the PP/CMSs@LDH@PZN composites reached a V-0 rating in the Vertical combustion tester (UL-94), and had a limiting oxygen index (LOI) value of 29.6%. Moreover, the heat release and toxic smoke emission were significantly lessened, which can be own to the adsorption of core–shell hybrid materials and the barrier effect of the P and N element crosslinked carbon layer. Herein, this work extends the idea of preparing multipurpose high-performance composites and designs and synthesizes an eco-friendly and efficient flame retardant with a double shell structure. [ABSTRACT FROM AUTHOR]

Ultrafine Mg/Al hydrotalcite particles (RMAH) were synthesized by co-precipitation in high-gravity environment generated by a rotating packed bed reactor with (NH 4 ) 2 CO 3 as precipitant. Sodium tripolyphosphate modified RMAH (S-RMAH) was investigated as potential flame retardant for polypropylene (PP) material. The RMAH and S-RMAH materials were characterized using XRD, SEM/EDS, TG–DTG, FT-IR, BET, particle size distribution, pH point of zero charge and so on. The S-RMAH particles which were coated by P 3 O 10 5 − possessed smaller particle sizes and narrower sizes range, and their surface property was modified from hydrophilic to hydrophobic nature. As novel functional fire-retarding nanofillers, the RMAH and S-RMAH were used to prepare PP/RMAH and PP/S-RMAH composites, aiming to investigate the effect of the nanofillers on the flammability, compatibility and mechanical properties of PP material. The thermal stability, morphological and flame retardant properties of the two composites were determined by SEM, TGA, LOI and UL94 analyses, and their mechanical properties were also characterized. The results showed that the RMAH and S-RMAH could significantly enhance the thermal stability, flammability and mechanical properties of PP material, and the S-RMAH had better performances as a flame retardant for PP than the RMAH. It offered a new approach to preparing ultrafine hydrotalcite nanoparticles with high anti-flaming performances. [ABSTRACT FROM AUTHOR]

A novel and bio-based adenosine triphosphate (ATP) pillared Mg Al layered double hydroxide (LDHs-ATP) was fabricated via calcination-reconstruction, followed by the incorporation of a highly efficient flame retardant into polypropylene (PP). The XRD result indicated that the interlayer channel of LDHs-ATP was increased to 16.6 Å. Indeed, the increase of the LDHs-ATP interlayer spacing promoted the uniform dispersion and thermal stability, which were further proved by the SEM and TG-DTG results. As expected, the PP/LDHs-ATP composite reached a LOI value of 29.1% and created a UL-94 V-0 rating with only 20 wt% LDHs-ATP loading. Furthermore, CCT illustrated that the peak heat release rate (PHRR), total heat release (THR) and total smoke release (TSR) of PP/LDHs-ATP composite exhibited a series of decreases of 55.9%, 39.5% and 56.4%, respectively, compared with that of Neat PP. [Display omitted] • A bio-based ATP pillared hydrotalcite (LDHs-ATP) was successfully fabricated. • With 20 wt% LDHs-ATP, the PP/LDHs-ATP reached LOI of 29.1% and got UL-94 V 0 rating. • The improvements attributed to synergistic effect from LDHs and ATP. [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]

Layered double hydroxide (LDH) can be used as a flame retardant (FR) for polypropylene (PP) because of its excellent flame retardancy and smoke-suppression effects. However, the agglomeration of LDH seriously affects its dispersity in the PP matrix, thus limiting its application as a FR polymer. This study aimed to enhance the dispersion of LDH in the PP matrix for improving its flame retardancy performance. Herein, a reactive triazine-based organic framework (TOF) was designed and formed by the in situ polymerisation of cyanuric chloride and melamine, and then the LDH surface was covered with TOF to obtain a novel core–shell FR (LDH@TOF), with TOF as the 'shell' and LDH as the 'core'. Subsequently, LDH@TOF was melted into the PP matrix as nanofillers to prepare PP and LDH@TOF composites (PP/LDH@TOF). As expected, the PP/LDH@TOF composites exhibited superior flame-retarding performance (limiting oxygen index of 29.2% and UL-94 V -0 rating) and favourable smoke-suppression performance at 20 wt% of LDH@TOF loading. Moreover, the peak heat release rate, total heat release and total smoke production of PP/LDH@TOF composites decreased by 29.9%, 12.1% and 12.4%, respectively, compared with those of PP and LDH composites. The outstanding flame retardancy properties of the PP/LDH@TOF composites were attributed to the better dispersibility of LDH@TOF in the PP matrix, the synergy of the physical barrier effect of nanosheets and the dense carbonisation acceleration of LDH@TOF. The findings of this study provide a highly efficient approach for functionalising LDH for expanding its application value of PP composites. [Display omitted] • Novel organic covalent structure TOF@LDH modified by triazinyl organic covalent skeleton are synthesised. • TOF@LDH has well dispersion and outstanding thermostability in PP. • TOF@LDH enhances the charring capability, flame retardancy and smoke suppression of PP. [ABSTRACT FROM AUTHOR]

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]

Due to the inherent defect of flammability of polypropylene (PP), a novel and highly efficient carbon microspheres@layered double hydroxides@copper lignosulfonate (CMSs@LDHs@CLS) flame retardant was designed and prepared, which was attributed to the strong electrostatic interaction between carbon microspheres (CMSs), layered double hydroxides (LDHs) and lignosulfonate as well as the chelation effect of lignosulfonate on copper ions, and then it was incorporated into the PP matrix. Significantly, CMSs@LDHs@CLS not only observably improved its dispersibility in PP matrix, but also simultaneously achieved excellent flame retardant properties for composites. With the addition of 20.0 % CMSs@LDHs@CLS, the limit oxygen index of CMSs@LDHs@CLS and PP composites (PP/CMSs@LDHs@CLS) reached 29.3 % and achieved the UL-94 V-0 rating. Cone calorimeter tests indicated that the peak heat release rate, total heat release and total smoke production of PP/CMSs@LDHs@CLS composites exhibited declines of 28.8 %, 29.2 % and 11.5 %, respectively, compared with those of PP/CMSs@LDHs composites. These advancements were attributed to the better dispersibility of CMSs@LDHs@CLS in PP matrix and illustrated that CMSs@LDHs@CLS observably reduced fire hazards of PP. The flame retardant property of CMSs@LDHs@CLS might relate to condensed phase flame retardant effect of char layer and catalytic charring of copper oxides. [ABSTRACT FROM AUTHOR]

A series of novel organic and/or inorganic-intercalated MgAl layered double hydroxides (S x Mo y -LDH) were designed and prepared via calcination-reconstruction, where the organic anion was stearic (S) and inorganic anion was MoO 4 2− (Mo). The intercalation of stearic and/or MoO 4 2− anions into the interlayer galleries of the LDH host layers was controlled by adjusting the mass ratios (x / y) of stearic acid to (NH 4) 2 MoO 4 , in which the stearic-intercalated LDH was obtained above the 1: 1 of the x / y mass ratio, and the MoO 4 2−-intercalated LDH was synthesized below the 1: 1 of the x / y mass ratio. Especially at x / y mass ratio of 1: 1, stearic and MoO 4 2− anions were co-intercalated into the interlayers of the S 1 Mo 1 -LDH to confer excellent flame-retardant properties. The morphology, chemical composition and structure of the as-prepared S 1 Mo 1 -LDH determined by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy and energy dispersive spectrometer (SEM/EDS) and thermogravimetry (TG) confirmed the co-intercalation of stearic and MoO 4 2− anions into the interlayer galleries. After adding the S x Mo y -LDH materials into polypropylene (PP) matrix, the flame retardant performance of the PP-composites was significantly enhanced compared with the neat PP. It was also noticed that different interlayer anions could provide different retardant performances, and the stearic-MoO 4 2−-co-intercalated LDH (S 1 Mo 1 -LDH) exhibited the highest thermostability and the best flame retardant performance owing to the synergistic effect of the interlayer stearic and MoO 4 2− anions as well the LDH host layers. Therefore, it was possible to obtain a certain intercalation state of the organic and inorganic anions by modulating the mass ratios (x / y) of organic to inorganic anions. Unlabelled Image • The organic and/or inorganic-intercalated MgAl-LDH, was successfully prepared. • At x/y mass ratio of 1: 1, stearic and MoO 4 2− anions were co-intercalated into the interlayers of the S 1 Mo 1 -LDH. • The S 1 Mo 1 -LDH provided excellent fire resistance to PP matrix owing to the interlayer stearic, MoO 4 2− and LDH. [ABSTRACT FROM AUTHOR]