Functional Group Effect on Char Formation, Flame Retardancy and Mechanical Properties of Phosphonate–Triazine-based Compound as Flame Retardant in Epoxy Resin

A series of novel flame-retardant thermosets were prepared by melt blending of phosphonate–triazine-based compound TNTP, triazine-based compound TN, and phosphonate-based compound TP, respectively. The curing systems were consisted of diglycidyl ether of bisphenol A (DGEBA) and 4,4′-diamino-diphenyl sulfone (DDS). The thermal behaviors and flame retardancy of these flame-retardant thermosets were investigated in terms of thermogravimetric analysis (TGA), limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter tests. TGA results showed that the char formation of flame-retardant thermosets could be significantly improved due to the presence of phosphonate moiety rather than triazine unit. It was found that the excellent flame retardant effect of TNTP was not contributed by either single group of phosphonate or triazine. An obvious synergic-effect on flame retardant produced by a combination of phosphonate and triazine moiety. The LOI value of TNTP-3/DGEBA/DDS could achieve 32.4% and reach UL-94 V-0 rating, while that of TN-3/DGEBA/DDS was 29.0% and failed in UL-94 test, and TP-3/DGEBA/DDS with a LOI value of 31.8% just reach UL-94 V-1 rating. Moreover, cone calorimeter test revealed that the incorporation of TNTP to epoxy thermoset with 1.5 wt % phosphorus content could result in a decrease of peak heat release rate (PHRR), total heat release (THR), average mass loss rate (AMLR), total smoke release (TSR), average CO yield (ACOY), and average CO₂ yield (ACO₂Y) compared with DGEBA/DDS control. The results from TGA data, scanning electronic microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) indicated TNTP modified thermosets had a comprehensive flame retardant mechanism, including the gas phase, condensed phase and phosphorus–nitrogen synergism mechanism. Furthermore, the mechanical properties of all the thermosets were also investigated by Izod impact strength and flexural property tests

Synthesis and Biological Activities of <i>O</i>,<i>O</i>-Dialkyl 1-((4,6-Dichloropyrimidin-2-yl)Carbamyloxy) Alkylphosphonates

<div><p></p><p>A series of new 1-((4,6-dichloropyrimidin-2-yl)carbamyloxy) alkylphosphonates were designed and synthesized. The structures of all the title compounds were confirmed by IR, ¹H-NMR, ³¹P-NMR and elemental analysis. The results of the bioassay showed that all of title compounds exhibited weak herbicidal activities against monocotyledons and <a href="http://dicotyledon" target="_blank">dicotyledon</a>s; however, some of them showed potential plant growth regulatory activities.</p></div

A Well-Defined Cyclotriphosphazene-Based Epoxy Monomer and Its Application as A Novel Epoxy Resin: Synthesis, Curing Behaviors, and Flame Retardancy

<div><p></p><p>A novel cyclotriphosphazene-based epoxy monomer, hexa-[4-(glycidyloxycarbonyl) phenoxy]cyclotriphosphazene (HGCP), was synthesized via a four-step synthetic route, and fully characterized by ¹H, ¹³C, and ³¹P NMR spectroscopy, high-resolution mass spectrometry, and elemental analysis. Thermosetting systems based on HGCP with three curing agents, for example, 4,4′-diaminodiphenylsulfone (DDS), 4,4′-diaminodiphenylmethane (DDM), and dicyandiamide (DICY), were used for making a comparison of their thermal curing behaviors. The curing behaviors were measured by differential scanning calorimetry. Moreover, flame retardancy of HGCP thermosetting systems was estimated by Limiting Oxygen Index (LOI) and Vertical Burning Test (UL-94). The resulting HGCP thermosetting systems exhibited better flame retardancy than the common epoxy resins diglycidyl ether of bisphenol A (DGEBA) and the regular brominated bisphenol A epoxy resin (TBBA) cured by DDS, respectively. When HGCP was cured by DDS, its thermosetting system gave the most char residues, met the UL-94 V-0 classification, and had a limiting oxygen index value greater than 35.</p> </div