Study on the crystal transformation of ammonium polyphosphate crystalline form V

The crystal transformation of ammonium polyphosphate crystalline form V (APPv) was studied. The effects of heating time and water content in the reactor were explored. The results showed that APPv underwent complete conversion to crystalline form II (APPii) when heated at 200°C. The pure and water-insoluble APPii was obtained under the alternate wet ammonia and dry ammonia atmosphere. Then, the thermal behavior of APPv and APPii was investigated. The TG analysis showed APPv had high thermal stability over the range of 300°C to 580°C, which was possibly due to its highly cross-linked structures.     

网状结构结晶V型聚磷酸铵的合成与表征

以85%的食品级磷酸为原料,三聚氰胺为缩合剂,合成了一种具有网状结构的结晶V型聚磷酸铵,对其水溶性、XRD、13C NMR、红外光谱、热重等进行了测试与表征,并与结晶I型、结晶Ⅱ型产品进行了对比。结果表明,本实验制备产品具有良好的耐水性, 其XRD图谱与结晶V型完全一致,其13C NMR及红外图谱表明该物质是以三嗪环为基本骨架的聚磷酸铵链交联网状结构。热重分析表明,700℃时该产品残重53.6%,大于结晶I型的40.29%及结晶II型的36.16%,初步显示该产品具有良好的高温热稳定性。     

The influence of KH-550 on properties of ammonium polyphosphate and polypropylene flame retardant composites

Ammonium polyphosphate (APP)/polypropylene (PP) composites were prepared by melt blending and extrusion in a twin-screw extruder. APP was first modified by a silane coupling agent KH-550 then added to polypropylene. The surface modification of APP by the coupling agent decreased its water solubility and its interface compatibility with the PP matrix. Limiting oxygen index (LOI) and thermogravimetric analysis (TGA) were used to characterize the flame retardant property and the thermal stability of the composites. The addition of APP improved the flame retardancy of PP remarkably. The crystal structures of APP/PP composites were characterized by X-ray diffraction (XRD). The results indicated that β-crystal phase PP may be formed. The structures and morphologies of APP, KH-550/APP and APP/PP composites were characterized by field-emission scanning electron microscope (FESEM). The mechanical property tests showed good mechanical properties of composite materials. Compared with unmodified one, the impact strength, tensile strength and elongation of modified APP/PP were all improved.     

可控合成具有氧化还原分区的Au-TiO2纳米哑铃光催化剂（英文）

太阳能因其环保清洁和来源丰富的特性被认为是最理想的资源之一.而光催化水分解是将太阳能转化为化学能的众多转换技术中,使用最广泛的策略之一.但H2和O2的逆反应显著降低了光催化水分解的效率,并且在实际应用中需要高昂的气体分离成本.因此,找到一种既可实现光催化有效水分解,同时抑制逆反应的策略具有十分重要的意义.到目前为止,为了实现光生电荷的有效分离,构建一维(1D)异质纳米结构光催化剂,被认为是抑制逆反应最有效的策略之一.其中哑铃状纳米结构,如Au-SiO2,Au-Fe3O4,Cu1.94S-CuS,Au-PbS(PbSe),Cu-Ag,Ag-Fe3O4,在促进光生电荷有效分离方面具有很大优势.但关于上述哑铃状纳米结构材料合成条件相对复杂,生长机理尚不清楚.对此,我们通过一种简便的合成策略制备了Au纳米棒/TiO2纳米哑铃结构光催化剂(Au NRs/TiO2 NDs).TiO2纳米颗粒(NP)仅包裹在Au NRs的两端.由于其独特的结构,可以实现电子空穴的定向分离,并减少它们在光照射下的复合,从而显著地提高电荷分离效率.同时,形成了氧化和还原反应的空间分离区域,从而有效地抑制了逆反应.通过SEM,XRD,和UV-Vis研究了可控合成哑铃状结构形态的关键因素.发现反应温度和酸度对Au NRs末端TiO2的包裹量有显著影响.基于此,我们提出了Au NRs/TiO2 NDs结构光催化剂的合成机理.并且通过改变加入的NaHCO3含量精准调节TiO2在Au NRs两端的包覆量,从而逐步提高Au NRs/TiO2 NDs光催化剂的产氢活性.在不断优化条件下,H2产率可达60264μmol/g/h,大约是报道的Au/TiO2光催化剂6倍.而电化学测试结果显示,在UV光照射下,Au NRs末端TiO2的包裹量越大,光电流相应越大.进一步证明光生电子定向从TiO2注入到Au NRs中,发生还原反应,而空穴留在TiO2上,发生氧化反应,从而实现氧化还原反应的分区.     

Controllable synthesis and catalysis application of hierarchical PS/Au core-shell nanocomposites

Polystyrene (PS)/gold (Au) core-shell nanocomposites with tunable size, high stability, and excellent catalytic activity have been synthesized by a facile method that combines the ionic self-assembly with the in situ reduction. The composition and stoichiometry, as well as its morphology and optical properties of these nanocomposites have been examined and verified by various characterization techniques. The size and the coverage of gold nanoparticles (NPs) can be simply tailored by changing the amount of 3-aminopropyltrimethoxysilane (APTES), the functionalization time, the protonation time, and the amount of chloroauric acid (HAuCl₄). The continuous red shifts of the localized surface plasmon resonance absorption of the Au NPs on the PS spheres are observed. Importantly, the obtained Au NPs with controllable and uniform size on the surfaces of amino-functionalized PS spheres exhibit excellent size-dependent catalytic properties for the reduction of 4-nitrophenol (4-NP) by NaBH₄.     

Controllable synthesis and micelles preparation of tri-block copolymers from 2,2-dimethyl-trimethylene carbonate and ethylene glycol

Amphiphilic triblock copolymer of poly(2,2-dimethyl-trimethylene carbonate)–poly(ethylene glycol)–poly(2,2-dimethyl trimethylene carbonate) (PDTC–PEG–PDTC) was synthesized by dihydroxyl capped PEG with molecular weight of 1,000, 4,000, and 6,000 in the presence of rare earth tris(2,6-di-tert-butyl-4-methylphenolate)s. The rare earth phenolates/PEG system could prepare triblock copolymer with predictable molecular weights with narrow molecular weight distribution. The polymers were characterized by nuclear magnetic resonance spectroscopy, gel permeation chromotography, and differential scanning calorimetry to confirm the structure. The micelles formed from the amphiphilic triblock copolymer were determined by fluorescence spectrophotometer and dynamic light scattering. The critical micelle concentrations fell in the range of 1.67∼5.25 mg/L. Transmission electron microscopy pictures showed that the micelles possess spherical morphology, and the diameters of micelles in number averaged scale ranged from 20–70 nm. The micelles formed from triblock amphiphilic copolymers were explored as carrier for indomethacin (IND), and they could enhance IND solubility in water dramatically.     

Microencapsulated ammonium polyphosphate with polyurethane shell: preparation,characterization, and its flame retardance in polyurethane

A series of polyurethane (PU) microencapsulated ammonium polyphosphate (MCAPP) were prepared by in situ polymerization from toluene‐2,4‐diisocyanate (TDI), polyethylene glycol (PEG), and pentaerythtritol (PER). And the structure was characterized by Fourier transform infrared spectroscopy (FTIR) and X‐ray photoelectron spectroscopy (XPS). Then it chose the optimal PEG constituent to design microcapsule from scanning electron microscopy (SEM) and water solubility test. The combustion and thermal degradation behaviors of PU blended APP or MCAPP were investigated by thermogravimetric analysis (TGA), UL‐94 test, and microcombustion calorimetry. The results showed that the PU/MCAPP had better thermal stability and flame retardance, due to the stable char forming by APP and PU shell. Moreover, the water resistance of flame retarded PU composite was greatly improved. Copyright © 2009 John Wiley & Sons, Ltd.     

Microencapsulated ammonium polyphosphate with epoxy resin shell: preparation,characterization, and application in EP system

Microencapsulated ammonium polyphosphate with an epoxy resin (EP) shell (MCAPP) was prepared by in situ method, and was characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), and thermgravimetric analysis (TGA). Compared to ammonium polyphosphate (APP), MCAPP has smaller particle sizes and lower water solubility. The effect of MCAPP on the fire performance of EP was studied by using limiting oxygen index (LOI) and UL‐94 tests. When the same loading levels of APP or MCAPP were added into EP, the LOI and UL‐94 tests show similar results. Tensile, bending, and impact strengths of the EP/APP and EP/MCAPP composites were also evaluated, and the results indicate that MCAPP has much less negative influence on the mechanical properties than APP. Copyright © 2010 John Wiley & Sons, Ltd.     

Flame retardancy and thermal degradation of halogen-free flame-retardant biobased polyurethane composites based on ammonium polyphosphate and aluminium hypophosphite

In this work, based on castor oil (CO), flame retardant polyurethane sealants (FRPUS) with ammonium polyphosphate (APP) and aluminum hypophosphite (AHP) were prepared. The synergistic flame retardant effects between APP and AHP on flame retardancy, thermal stability, and flame retardant mechanisms of FRPUS were investigated. It was found that when the mass ratio of APP and AHP was 5:1, the limiting oxygen index (LOI) value of FRPUS increased to 35.1%, In addition, at this ratio, the parameters from cone calorimeter testing (CCT) were reduced; these parameters include peak heat release rate (PHRR), total heat release (THR), smoke production rate (SPR) and total smoke production (TSP). The thermal decomposition behavior of the FRPUS was investigated by thermogravimetric analysis (TGA). The results showed that AHP improved the thermal stability of the PUS/APP system and increased char residue at high temperatures. Moreover, the residual carbon was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM), gas phase pyrolysis products were investigated by thermogravimetric analysis/infrared spectrometry (TG-IR) and thermogravimetric analysis/mass spectrometry (TG-MS). It was observed that the flame retardant mechanisms of the APP/AHP system was the combination of gas and condensed phase flame retardant mechanisms.     

Preparation and characterization of microencapsulated ammonium polyphosphate with polyurethane shell by in situ polymerization and its flame retardance in polyurethane

Microencapsulated ammonium polyphosphate (APP) with polyurethane (MCAPP) was prepared by in situ polymerization of pentaerythtritol (PER) and toluene‐2,4‐diisocyanate (TDI) in the presence of added APP. MCAPP was then incorporated into polyurethane (PU) to obtain flame retarded PU/MCAPP. Fourier transform infrared (FT‐IR) and X‐ray photoelectron spectroscopy (XPS) showed that APP was encapsulated by a layer of PU. It found that the optimal reaction time was 8 hr and microencapsulation led to an improvement in water leaching from scanning electron microscopy (SEM) and determination of water resistance. Thermal degradation of flame retarded PU was also investigated by thermogravimetric analysis (TGA). UL‐94 test and SEM were performed before and after water treatment at 75°C for seven days, and the results showed that PU loading of 30% MCAPP can maintain the V‐0 level, due to the shield effect of microencapsulation. Copyright © 2008 John Wiley & Sons, Ltd.     

CdS/有机复合纳米材料的可控合成与表征

本文在室温下,以正丁胺为模板剂,二硫化碳为硫源,制得了CdS/有机复合纳米材料.采用XRD、FTIR、SEM、TEM、元素分析以及热重分析(TG)等测试手段对产物进行了表征.实验结果表明产物的结构是CdS(CH3CH2CH2CH2NHCSNHCH2CH2CH2CH3) (CS2).随着正丁胺与二硫化碳的摩尔比、陈化时间...     

磷酸催化合成2,4-二叔丁基苯酚的研究

研究了以磷酸为催化剂,苯酚和叔丁醇为原料合成2,4-二叔丁基苯酚。合成产物经过利用受阻酚的性质分离提纯,得到高纯度的2,4-二叔丁基苯酚,并考察了影响反应的因素。结果表明:酚醇摩尔比为1∶3,催化剂85%磷酸的用量为10m L,反应时间为5h,反应温度为60℃是最适宜的反应条件;产物收率达57.1%。     

Influence of the presence of surfactants and humic acid in waters on the indophenol-type reaction method for ammonium determination

This work has evaluated the influence of humic acid and/or surfactants in the quantification of ammonium in waters with the indophenol-type reaction method. Thymol has been employed with the colorimetric method for sample ammonium concentrations between 0.25 and 1 mg L⁻¹. In addition, SPE/diffuse reflectance method has been used for quantification of ammonium at low concentrations (between 0.025 and 0.25 mg L⁻¹). Matrix effect owing to humic substances were observed with the colorimetric method when the concentration was equal or higher than 25 mg L⁻¹. Lower concentrations of humic compounds produced matrix effects with the more sensitive SPE/diffuse reflectance method. Generalized H-point standard addition method (GHPSAM) was employed for evaluating the effect of humic acids and for eliminating the bias error produced by humic acids. Real water samples of different types were analyzed and accurate results for ammonium concentration were obtained with both procedures in presence or absence of humic acids. Cationic and anionic surfactants inhibited the derivatization reaction at percentages up to 0.001% and 0.5%, respectively, and non-ionic surfactants at percentages of 5.5%     

Syntheses and characterization of elpasolite-type ammonium alkali metal hexafluorometallates(III)

Crystal structures of three fluorides (NH₄)₂NaFeF₆, (Fe), (NH₄)₂NaGaF₆, (Ga), and (NH₄)₂NaCrF₆, (Cr), as well as a substituted compound [(NH₄)_1−xK_x]₂KAlF₆ (x≈0.17), (Al), have been refined using single-crystal and powder X-ray diffraction techniques. All these four ammonium hexafluorides have a cubic elpasolite-type structure and crystallize in the space group Fm3¯m with lattice constants a=8.483(3), 8.450 (3), 8.4472(2) and 8.724(3) Å for compounds (Fe), (Ga), (Cr) and (Al), respectively. The effective ionic radius of the ammonium ion calculated from those compounds has a mean value of R=1.729 Å for CN=12. An ultraviolet-visible absorption spectrum of (NH₄)₂NaCrF₆, measured at room temperature, gives a crystal field (Dq=1575 cm⁻¹) and Racah parameters (B=758 cm⁻¹ and C=3374 cm⁻¹). Abnormal anisotropic thermal parameters of fluorine atoms have been observed in the compound (Al), and interpreted to arise from four strong hydrogen bonds (F…H-N) that are distributed in a square form around each fluorine atom.     

Preparation of microencapsulated ammonium polyphosphate with montmorillonite‐melamine formaldehyde resin and its flame retardancy in EVM

Microencapsulated ammonium polyphosphate (MMT‐MF‐APP) with a montmorillonite‐melamine formaldehyde resin coating layer was successfully prepared by in situ polymerization. The product was characterized by Fourier‐transform infrared, X‐ray photoelectron spectroscopy, and scanning electron microscopy. Water absorption analysis showed that the microencapsulation of APP with the MMT‐MF resin leads to a decrease in the particle's water solubility. The microcapsules also exhibited better mechanical properties and higher flame retardancy in the ethylene–vinyl acetate copolymer with high vinyl acetate content (EVM) rubber compared with the common ammonium polyphosphate. Moreover, thermogravimetric analysis results showed that the EVM composites with MMT‐MF‐APP and dipentaerythritol (DPER) as flame retardants possess higher thermal stability than those with common APP and DPER as flame retardants. Copyright © 2011 John Wiley & Sons, Ltd.     

Flammability and combustion properties of ammonium polyphosphate-/poly(acrylic acid)- based layer by layer architectures deposited on cotton,polyester and their blends

Layer by layer architectures consisting of four layer repetitive unit (QL) based on poly(diallydimethylammonium chloride)/poly(acrylic acid)/poly(diallydimethylammonium chloride)/ammonium polyphosphate have been deposited on cotton, polyester and their blends in order to promote the formation of an aromatic and stable carbonaceous structure (char) during combustion. The LbL-treated fabrics have been subjected to flammability (reaction to flame application) and combustion (reaction to different external heat fluxes) tests. The coatings were able to remarkably enhance the char formation of each substrate just after 1QL deposition; furthermore, 5 and 10QL assemblies have favoured the formation of intumescent-like structures with further improvement of the final residue. As a consequence, the treated fabrics have shown a strong reduction of the flammability (afterglow and incandescent melt dripping suppression) and combustion (reduced heat released). Infrared spectroscopy has pointed out the aromatic nature of the residues left after the combustion.     

Microencapsulated ammonium polyphosphate with urea–melamine–formaldehyde shell: preparation,characterization, and its flame retardance in polypropylene

Microencapsulated ammonium polyphosphate (MCU‐APP) with urea–melamine–formaldehyde (UMF) resin is prepared by in situ polymerization, and is characterized by FTIR and XPS. The microencapsulation of APP with the UMF resin leads to a decrease in the particle's water solubility. The flame retardant actions of MCU‐APP and APP in PP are studied using limiting oxygen index (LOI) and UL‐94 test, and their thermal stability is evaluated by thermogravimetric analysis. It is found that the LOI value of the PP/MCU‐APP composite is higher than the value of the PP/APP composite. In comparison with the PP/MCU‐APP composites, the LOI values of the PP/MCU‐APP/DPER ternary composites at the same additive loading increase, and UL‐94 ratings of most ternary composites are raised to V‐0. The water‐resistant properties of the PP composites containing APP and MCU‐APP are studied. Moreover, the combustion behavior of the PP composites is investigated by the cone calorimeter. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis and structural characterization of 3,4-diphenylcyclopenta-2,4-diene-1 thione and its reactivity with V(V)

In the first part of this work, we have studied the reactivity of an ethanolic solution of diphenylthiocarbazone (C₁₃H₁₂N₄S) with an aqueous solution of vanadium(V), leading to a new compound C₁₇H₁₂S (L). This compound was crystallographically characterized and identified by XRD. This technique reveals no metal in the structure. Then, we reacted L with the same metal, producing a dimeric complex V₂O₄(L)₂(H₂O)₂(OH)₂ (C1), characterized by elemental analysis, IR, UV–Visible, ¹H NMR, ¹³C NMR, and ⁵¹V NMR spectra. A probable structure has been proposed.     

磷化淀粉的合成及其与聚磷酸铵协效阻燃聚乳酸的性能研究

利用9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)和马来酸酐(MA)对淀粉进行改性得到磷化淀粉(DOPOMASt),通过红外光谱(FTIR)、核磁共振谱(1H-NMR)和X射线光电子能谱(XPS)确定其结构.利用DOPOMASt作为碳源,与聚磷酸铵(APP)复配后通过熔融共混制备了阻燃聚乳酸(PLA)...     

Microencapsulation of ammonium polyphosphate with PVA–melamine–formaldehyde resin and its flame retardance in polypropylene

With a shell of PVA–melamine–formaldehyde resin, microencapsulated ammonium polyphosphate (VMFAPP) is prepared by in situ polymerization and characterized by FTIR and XPS. Microencapsulation gives VMFAPP better water resistance and flame retardance compared with APP in PP. Thermal stability and fire resistance behavior have been analyzed and compared. The LOI value of the PP/VMFAPP composite is higher than that of the PP/APP composite. The UL 94 ratings of most of the PP/VMFAPP composites are V‐0, whereas PP/APP gives no rating at the 30% additive level. The water resistant properties of the PP composites are studied. Results of the cone calorimeter experiment show that VMFAPP is an effective flame retardant in PP compared with APP. The thermal degradation behaviors of APP and VMFAPP have been studied using TG and dynamic FTIR. Copyright © 2008 John Wiley & Sons, Ltd.