Natural antioxidant functionalization for fabricating ambient-stable black phosphorus nanosheets toward enhancing flame retardancy and toxic gases suppression of polyurethane.

Herein, as a natural antioxidant, tannin (TA) is firstly used to functionalize black phosphorous (BP) nanosheets to improve the ambient stability and toxic suppression, thus decreasing the fire hazards of polymer materials. Compared to pure BP nanosheets, higher temperature for thermal oxidation decomposition is achieved for TA-BP nanosheets, directly confirming the ambient stability of TA-BP nanosheets. Meanwhile, from high resolution TEM and XPS results, TA-BP nanosheets after being exposed at air for 10 days present well-organized crystal structure and low POx bonds content. Cone calorimeter results illustrate that the incorporation of 2.0 wt% TA-BP nanosheets significantly decreases the peak value of heat release rate (-56.5 %), total heat release (-43.0 %), CO2 concentration (-57.3 %) of TPU composite. Meanwhile, with addition of low to 1.5 wt%, the release of highly-toxic CO gas is significantly suppressed, confirmed by lower peak value (0.52 mg/m3) and decreased total release amount (-55.1 %). The obviously enlarged tensile strength (36.7 MPa) and desirable elongation at break (622 %) are also observed. This strategy not only firstly adopts bio-based antioxidant to impart excellent environmental stability for BP nanosheets, but also promotes the promising potentials of BP nanosheets in the fire safety application of polymer composites.

Phosphorus-Containing Flame Retardants from Biobased Chemicals and Their Application in Polyesters and Epoxy Resins.

Phosphorus-containing flame retardants synthesized from renewable resources have had a lot of impact in recent years. This article outlines the synthesis, characterization and evaluation of these compounds in polyesters and epoxy resins. The different approaches used in producing biobased flame retardant polyesters and epoxy resins are reported. While for the polyesters biomass derived compounds usually are phosphorylated and melt blended with the polymer, biobased flame retardants for epoxy resins are directly incorporated into the polymer structure by a using a phosphorylated biobased monomer or curing agent. Evaluating the efficiency of the flame retardant composites is done by discussing results obtained from UL94 vertical burning, limiting oxygen index (LOI) and cone calorimetry tests. The review ends with an outlook on future development trends of biobased flame retardant systems for polyesters and epoxy resins.

Synthesis, characterization of phosphorus-containing copolyester and its application as flame retardants for poly(butylene succinate) (PBS).

Two novel phosphorus-containing copolyesters were synthesized by direct polycondensation reaction of phenyl dichlorophosphate, 1,4-succinic acid and 1,4-butanediol using stannous chloride (SnCl2) and 4-Methylbenzenesulfonic acid as catalyst, and its chemical structures were identified by 1H and 31P nuclear magnetic resonances (1H and 31P NMR). The resulting phosphorus-containing poly(butylene succinate) (PPBS) was characterized by X-ray diffraction (XRD), polarized optical microscope (POM), thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). PPBS can be as a flame retardant for commercial poly(butylene succinate) (PBS). A series of flame retardant composite materials were produced by melt-blending of PBS and PPBS. The comprehensive flame retardant property of composite materials was evaluated by limited oxygen index (LOI). While 20 wt % of PPBS was added into PBS resin, good flame retardant properties could be obtained. Composite materials can have much better flame retardancy (LOI = 30) than neat PBS resin. Thermogravimetric analysis (TGA) showed that the weight loss of PBS was decreased by the introduction of PPBS. In addition, possible flame retardancy mechanism of PPBS in composite materials was analyzed by SEM photos of char residue.

Synthesis of a Novel Phosphorus-Containing Flame Retardant Curing Agent and Its Application in Epoxy Resins.

A novel phosphorus-containing compound diphenyl-(2,5-dihydroxyphenyl)-phosphine oxide defined as DPDHPPO was synthesized and used as flame retardant and curing agent for epoxy resins (EP). The chemical structure was well characterized by Fourier transform infrared (FTIR) spectroscopy, 1H, 13C and 31P nuclear magnetic resonance. The flame retardant properties, combusting performances and thermal degradation behaviors of the cured epoxy resins were investigated by limiting oxygen index (LOI), vertical burning tests (UL-94), cone calorimeter and thermogravimetric analysis (TGA) tests. The morphologies and chemical compositions of char residues for cured epoxy resins were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The water resistant properties were evaluated by putting the samples into distilled water at 70 degrees C for 168 h. The results revealed that the EP/40 wt% DPDHPPO/60 wt% PDA thermosets successfully passed UL-94 V-0 flammability rating and the LOI value was as high as 31.9%. The cone tests results revealed that the incorporation of DPDHPPO efficiently reduced the combustion parameters of epoxy resins thermosets, such as heat release rate (HRR), total heat release (THR) and so on. The TGA results indicated that the introduction of DPDHPPO promoted epoxy resins matrix decomposed ahead of time compared with that of pure EP and led to a higher char yield and thermal stability at high temperature. The morphological structures and analysis of XPS of char residues revealed that DPDHPPO benefited to the formation of a sufficient, compact and homogeneous char layer with rich flame retardant elements on the epoxy resins materials surface during combustion. After water resistance tests, EP/40 wt% DPDHPPO/60 wt% PDA thermosets still remained excellent flame retardancy, the moisture absorption of epoxy resins thermosets decreased with the increase of DPDHPPO contents in the thermosets due to the existing of P-C bonds and the rigid aromatic hydrophobic structure.

Conferring flame retardancy on cotton using novel halogen-free flame retardant bifunctional monomers: synthesis, characterizations and applications.

Two novel halogen-free phosphorous-nitrogen flame retardant bifunctional monomers were synthesized and characterized using attenuated total reflectance/Fourier transform-infrared (ATR/FT-IR) and electrospray ionization mass spectrometry ((+)ESI-MS). The monomers were applied separately and graft polymerized on cotton in the presence of the thermal initiator K(2)S(2)O(8). The performance of each monomer was evaluated using thermal gravimetric analysis (TGA), grafting efficiency, and vertical flame test. It was shown that the performance of N,N-dimethyl di(acryloyloxyethyl)phosphoramide (DMDAEP) (monomer 2) as flame retardant outperformed that of ethyl di(acryloyloxyethyl)phosphorodiamidate (EDAEP) (monomer 1). The superior performance of DMDAEP was attributed to the presence of more nitrogen atoms compared to EDAEP. The increased nitrogen content in DMDAEP increased the synergistic effect of the P-N system. Cotton treated using padding methods showed more promising results than cotton treated by exhaust methods.

Synthesis and application in polypropylene of a novel of phosphorus-containing intumescent flame retardant.

A novel phosphorus-containing triazine oligomer poly(2-morpholinyl-4-penta-erythritol phosphate-1,3,5-triazine) (PMPT) was synthesized as a kind of tri-component intumescent flame retardant (IFR). The chemical structure of PMPT was characterized by FTIR, 1H-NMR and 31P-NMR, and the mechanical and flammability properties of FR-PP were measured. The FTIR results showed that the expected chemical reactions had  happened at each step. The 1H-NMR and 31P-NMR spectra also agreed with the chemical structure of PMPT. The slight effect of PMPT on the mechanical properties of FR-PP suggested that PMPT and PP are compatible. The high limited oxygen index (LOI) values of FR-PP revealed that PMPT was an efficient IFR and there was the synergistic effect between PMPT and ammonium polyphosphate/ pentaerythritol (APP/PER).

Silicon-containing soybean-oil-based copolymers. Synthesis and properties.

New silicon-containing soybean-oil-based copolymers were prepared from soybean oil, styrene, divinylbenzene, and p-trimethylsilylstyrene by cationic polymerization using boron trifluoride etherate as initiator. Soxhlet extraction and NMR spectroscopy indicate that the copolymers consist of a cross-linked network plasticized with varying amounts of oligomers and unreacted oil. This soluble fraction increases when the SiST content in the feed increases, according to a lower reactivity of this monomer. The thermal, dynamomechanical, and flame-retardant properties of these materials were examined. Thermosets with glass transition temperatures ranging from 50 to 62 degrees C, which are thermally stable below 350 degrees C, and with LOI values from 22.6 to 29.7 were obtained. Their properties suggest that these materials may prove to be useful alternatives for current non-renewable-based thermosets and that the flame-retardant properties of vegetable-oil-based thermosets can be improved by adding covalently bonded silicon to the polymer.