Li Dang

To improve the flame retardancy and smoke suppression of magnesium hydroxide (MH) in flexible PVC, a hierarchical flame retardant (MH‐P2@Fe) was designed via dual‐layer coating of polydopamine (PDA) and polydichlorophosphazene (PDCP) followed by Fe(OH) ₃ loading. The introduction of Fe(OH) ₃ enhanced the thermal stability of the PDCP coating, raising its onset decomposition temperature ( T ₀₅ ) to 343.6°C. Adding 20 phr of MH‐P2@Fe to PVC gave a limiting oxygen index of 25.6%, a UL‐94 V‐0 rating, and reductions in peak heat release rate (20.7%), total heat release (8.89%), peak smoke production rate (37.5%) and total smoke production (28.6%) compared to PVC/MH. Thermogravimetric analysis (TGA)‐based quantitative analysis showed that iron oxides (Fe ₂ O ₃ /Fe ₃ O ₄ ) derived from the decomposition of Fe(OH) ₃ possess a strong catalytic char‐forming capacity of 8.44 per unit mass, promoting early dehydrochlorination and deep aromatization to form a continuous, highly graphitized inorganic–organic char layer (MgO and Fe ₂ O ₃ /Fe ₃ O ₄ ). In the gas phase, phosphorus radicals and water vapor quenched active radicals and diluted combustible gases. Moreover, the dual‐layer coating improved interfacial adhesion, resulting in higher impact strength and tensile modulus than neat PVC, although tensile strength decreased. This work provides an effective halogen‐free flame retardant for PVC with balanced performance.

To address the high flammability and toxic smoke emission of flexible PVC (fPVC), a Mg–Mo–P multi-component flame retardant (MO@MH-PEPE) was constructed by modifying MoO ₃ -hybridized Mg(OH) ₂ with phenolic epoxy phosphate ester.

To enhance the interfacial compatibility and fire safety of polyvinyl chloride (PVC)/molybdenum trioxide‐doped magnesium hydroxide (MO@MH) composites, three chain‐length‐varied silicon‐phosphorus polyether modifiers (ABP₂₀₀, ABP₁₀₀₀, and ABP₂₀₀₀) were synthesized and characterized. Magnesium‐molybdenum‐silicon‐phosphorus multicomponent flame retardants (MO@MHABP) were subsequently prepared via wet modification. The chain‐length‐dependent mechanical behavior of PVC composites was systematically evaluated through combined experimental characterization and molecular dynamics (MD) simulations. Static mechanical tests revealed that yield strength, tensile strength, and impact strength of PVC/MO@MH composite were all improved by inducing ABP modifiers, with the shortest‐chain ABP₂₀₀ showing optimal enhancement. Dynamic mechanical analysis revealed increased storage/loss modulus and glass transition temperatures for PVC/MO@MHABP, indicating restricted chain mobility. Interface interaction models (Turcsányi equation and Kubát model) combined with MD simulations demonstrated that the shortest‐chain modifier (ABP₂₀₀) enhanced interfacial adhesion through the strongest Cl–NH interactions (supported by the most negative ΔE values). Cone calorimetry tests indicated that ABP modification decreased the heat release rate and total heat release of PVC/MO@MH composites but did not significantly improve smoke suppression. This study provides valuable insights into interfacial regulation and performance optimization in PVC composites.

A trade‐off dilemma exists for simultaneously improving the mechanical properties and flame resistance of flexible polyvinyl chloride (fPVC)/magnesium hydroxide (MH) composites. In this study, epoxy phosphate ester (EPE), a hydrophobic surface modifier of MH, was synthesized using a self‐emulsification method. After modification, EPE was bonded to the surface of MH (MHEPE) without altering its morphology. The results of limiting oxygen index and cone calorimetry tests indicated that fPVC/MHEPE exhibited better flame retardancy and smoke suppression effects than did fPVC/MH. The peak of the heat release rate, total heat release, peak of the smoke production rate, and total smoke production of the fPVC/MHEPE composite were 206.0 kJ m⁻², 45.90 MJ m⁻², 0.0729 m² s⁻¹, and 9.88 m², which were 8.64%, 14.00%, 27.61%, and 9.02% lower than those of the fPVC/MH composite, respectively. For the fPVC/MHEPE composite, a compact and continuous char residue formed, which could inhibit heat and flammable volatile migration between the matrix and burning zones. In the gas phase, the dilution effect of H₂O vapor reduced the concentrations of O₂ and flammable volatiles. The free‐radical quenching effect of ·PO and ·PO₂ also played a vital role in extinguishing flame and terminating combustion. Further, the introduction of EPE improved the tensile and impact strengths of the fPVC/MH composites because of the excellent interfacial compatibility between MHEPE and the fPVC matrix. This study provides a simple and workable solution for the trade‐off dilemma, and the remarkable flame retardancy and mechanical properties of the fPVC/MHEPE composite render it a promising cable material.

Maleic anhydride-modified homopolymerized polypropylene (PP-g-MAH) and maleic anhydride-modified polyolefin elastomer (POE-g-MAH) were used as bulking agents to improve the poor processing and mechanical properties of highly filled composites due to high filler content. In this study, a series of linear low-density polyethylene (LLDPE)/magnesium hydroxide (MH) composites were prepared by the melt blending method, and the effects of the compatibilizer on the mechanical properties, flame retardancy, and rheological behavior of the composites were investigated. The addition of the compatibilizer decreased the limiting oxygen index (LOI) values of the composites, but they were all greater than 30.00%, which belonged to the flame retardant grade. Mechanical property tests showed that the addition of the compatibilizer significantly increased the tensile and impact strengths of the LLDPE/60MH (MH addition of 60 wt%) composites. Specifically, the addition of 5 wt% POE-g-MAH increased 154.07% and 415.47% compared to the LLDPE/60MH composites, respectively. The rotational rheology test showed that the addition of the compatibilizer could effectively improve the processing flow properties of the composites. However, due to the hydrocarbon structure of the compatibilizer, its flame retardant properties were adversely affected. This study provides a strategy that can improve the processing and mechanical properties of highly filled composites.

In this paper, an effective flame retardant consisting of hierarchical magnesium hydrate (MH) nanosheets doped with molybdenum trioxide nanoparticles (MO@MH) was successfully synthesized via a hydrothermal process. Then, MO@MH, MH, and MH/MO were respectively incorporated into flexible polyvinyl chloride (fPVC) to prepare a series of composites via melt blending. The results of limiting oxygen index (LOI), UL‐94, and cone calorimetry test showed that MO@MH exhibited better flame retardancy and smoke suppression than MH and MH/MO due to the synergistic effect of MO and MH, and the hierarchical structure of MO@MH. With the addition of 20 phr MO@MH, LOI value of fPVC was increased from 23.9% to 33.8% , and UL‐94 reached V0 rating. The peak heat release rate, total heat release, peak smoke production rate, and total smoke production were decreased to 143.0 kW/m², 44.9 MJ/m², 0.0093 m²/s and 29.4 m², respectively. The thermogravimetric analysis results suggested that MO@MH greatly promoted the dehydrochlorination of fPVC at lower temperature, so that more compact and continuous char residues were formed. The Fourier transform infrared spectroscopy results indicated that MO@MH can prevent chain scission and oxidation of fPVC carbonaceous backbone, and as a result less smoke was released.

A simple hydrothermal method was developed in this study to synthesize hydrophobic calcium sulfate hemihydrate whiskers in the presence of stearic acid. The morphology of the whiskers synthesized under different conditions was characterized by scanning electron microscopy, and their average aspect ratio was also estimated. The optimum synthesis conditions are determined as follows: the concentrations of Na2SO4 and CaCl2 solution for preparing the precursor are 1.1 mol/L; the precursor content in the autoclave is 10 wt％; the hydrothermal reaction temperature is 150 C; and the hydrothermal reaction time is 4 h, respectively. Glycol was used to promote the dispersion of stearic acid in the seriflux. The results show that the hydrophobic calcium sulfate hemihydrate whiskers can be obtained with stearic acid as surfactant, and their average aspect ratio can reach about 91.