The effect of morphology on the flame-retardant behaviors of melamine cyanurate in PA6 composites

Synthesis, Characterization of sym-2,4,6-trisubstituted-s-Triazine Derivatives and Their Effects on Flame Retardancy of Polypropylene Composites

Polypropylene (PP) is flammable material, which brings latent danger to the environment and human society. Therefore, developing new environmentally friendly and effective flame-retardant is one of the most important ways to improve the flame retardancy of PP and improve safety during its lifetime. Herein, we describe the synthesis of five sym-2,4,6-trisubstituted-s-triazine derivatives, namely, N2,N4,N6-triphenyl-1,3,5-triazine-2,4,6-triamine (TAT), N2,N4,N6-tris(4-bromophenyl)-1,3,5-triazine-2,4,6-triamine (TBAT), N2,N4,N6-tris(4-chlorophenyl)-1,3,5-triazine-2,4,6-triamine (TCAT), 4,4′,4″-((1,3,5-triazine-2,4,6-triyl) tris(azanediyl)) triphenol (THAT), and N2,N4,N6-tris(4-methoxyphenyl)-1,3,5-triazine-2,4,6-triamine (TMAT), from the reaction of cyanuric chloride and p-substituted aniline employing conventional heating or microwave irradiation. The prepared compounds characterized by different techniques, such as Fourier-transform infrared (FTIR), Ultra-Violet and Visible (UV-Vis), Nuclear Magnetic Resonance spectroscopy (1H-NMR and 13C-NMR), Thermogravimetric Analysis (TGA), and differential scanning calorimetry (DSC). The effect of substituent on the aniline moiety has great impact on its thermal stability, as observed from the TGA and DSC data. Based on the TGA and DSC results, three triazine derivatives TAT, TBAT, and TMAT were used as charring agents in the presence of different proportions of ammonium polyphosphate (APP) to form an intumescent flame-retardant (IFR) system, to improve the flame retardancy of PP. The flammability property of PP was investigated by a vertical burning test (UL94). The results of UL94 revealed that the TXAT/APP (IFR) system influence the PP and could improve the flame retardancy of PP. Best results were obtained with the mass ratio of APP and TXAT 2:1. When the IFR loading was 25 wt%, it displayed great influence and passed V-0 with TMAT, and V-1 with both TAT and TBAT in the UL94 test.

Flame Inhibition and Charring Effect of Aromatic Polyimide and Aluminum Diethylphosphinate in Polyamide 6

An aromatic macromolecular polyimide (API) was synthesized and characterized, and used as a synergistic charring flame retardant in glass fiber reinforced polyamide 6 (GF/PA6). API and aluminum diethylphosphinate (ADP) exhibited better flame inhibition behavior and synergistic charring flame retardant behavior compared with ADP alone. The 5%API/7%ADP/GF/PA6 sample achieved the lower peak value of the heat release rate (pk-HRR) at 497 kW/m² and produced higher residue yields of 36.1 wt.%, verifying that API and ADP have an outstanding synergistic effect on the barrier effect. The API/ADP system facilitated the formation of a carbonaceous, phosphorus and aluminum-containing compact char layer with increased barrier effect. FTIR spectra of the residue and real-time TGA-FTIR analysis on the evolved gases from PA6 composites revealed that API interacted with ADP/PA6 and locked in more P⁻O⁻C and P⁻O⁻Ar content, which is the main mechanism for improving flame inhibition and charring ability. In addition, the API/ADP system improved the mechanical properties and corrosion resistance of GF/PA6 composites compared to ADP alone.

Integrated effect of supramolecular self-assembled sandwich-like melamine cyanurate/MoS2 hybrid sheets on reducing fire hazards of polyamide 6 composites

A novel strategy of using supramolecular self-assembly for preparing sandwich-like melamine cyanurate/MoS₂ sheets as the hybrid flame retardants for polyamide 6 (PA6) is reported for the first time. The introduction of MoS₂ sheets function not only as a template to induce the formation of two-dimensional melamine cyanurate capping layers but also as a synergist to generate integrated flame-retarding effect of hybrid sheets, as well as a high-performance smoke suppressor to reduce fire hazards of PA6 materials. Once incorporating this well-designed structures (4wt%) into PA6 matrix, there resulted in a remarkable drop (40%) in the peak heat release rate and a 25% reduction in total heat release. Moreover, the smoke production and pyrolysis gaseous products were efficiently suppressed by the addition of sandwich-like hybrid sheets. The integrated functions consisting of inherent flame retarding effect, physical barrier performance and catalytic activity are believed to the crucial guarantee for the reduced fire hazards of PA6 nanocomposites. Furthermore, this novel strategy with facile and scalable features may provide reference for developing various kinds of MoS₂ based hybrid sheets for diverse applications.

New insight into the preparation of flame-retardant thermoplastic polyether ester utilizing β-cyclodextrin as a charring agent

The past decade has witnessed remarkable progress of the development and amelioration of thermoplastic polyether ester elastomer (TPEE), showing its promising wide-range utility. Herein we unraveled an unprecedented research to utilize β-cyclodextrin (β-CD) with perfect charring ability in TPEE in substitution of toxic halogen flame retardants. The TPEE/phosphorous–nitrogen flame retardants (P-N FR) (aluminum diethylphosphinate and melamine polyphosphate)/β-CD system was created and the flame retardance effects were determined using the limiting oxygen index (LOI) and the vertical burning test (UL94), while the charring effects of β-CD were measured by thermogravimetric analysis (TGA), laser Raman spectroscopy (LRS), and scanning electron microscopy (SEM). Besides, the mechanical properties and the morphology were tested by the universal testing machine and SEM. Results indicate that with 10 wt% of β-CD added to the TPEE/25 wt% P-N FR systems, the UL94 can reach to V-0 grade and the tensile strength of this blend was kept above 10 MPa, which can be applied in practice. To our delight, β-CD promoted the formation of stable and compact carbonaceous char, preventing the melt dripping and enhancing the properties and the charring mechanism was better studied by real-time Fourier transform infrared spectra. Being easy to construct, sustainable, and economic, the TPEE composite modified by β-CD and P-N FR is a reliable and widely applicable novel fire retardation material.

Synergistic effects of BHDB-IPC with AlPi/MCA on flame retarding TPEE

The deoxybenzoin-based copolyarylate BHDB-IPC with perfect charring ability was synthesized.