Flame-retardant properties and synergistic effect of ammonium polyphosphate/aluminum hydroxide/mica/silicone rubber composites

The flammability behaviors of ammonium polyphosphate/aluminum hydroxide/mica/silicone rubber (APP/Al[OH]₃/mica/SiR) ceramifying composites containing APP, Al[OH]₃, and mica are investigated by cone calorimeter test. The thermal degradation and the synergistic effect of APP/Al(OH)₃/mica/SiR composites are investigated by thermal gravimetric analysis, X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. APP/Al(OH)₃/mica/SiR composites with 25 wt% of APP, 20 wt% of Al(OH)₃, 25 wt% of mica, and 30 wt% SiR presents a much lower total heat release, the value of peak heat release rate (PHRR), the maximum average heat release rate, the longest time to ignition, and time to the PHRR (t_PHRR), compared with the flame-retardant properties from composites with filler of APP and mica or APP and Al(OH)₃ alone. The results indicate that there is an excellent synergism in APP, Al(OH)₃, and mica, which endows APP/Al(OH)₃/mica/SiR composites with both good flame retardancy and fire prevention. The study on the synergism effect between fire prevention and flame retardancy of APP/Al(OH)₃/mica/SiR composites indicates that compounds containing P-O-Al are formed due to the reaction between APP and Al(OH)₃ during combustion in the early stage and a coherent, dense, and sealed structure is formed due to the reaction in mica, phosphates, and the thermal decomposition products of SiR during combustion in the later stage.     

Synthesis of Quaternary Ammonium Salts with Novel Counterions

The preparations of quaternary ammonium compounds from various tertiary amines and the (environmentally friendly) alkylation agent dimethyl carbonate were carried out. The effects of reaction temperature, reaction time, material mol ratio and solvent dosage on quaternization were examined, and the optimum reaction conditions were determined. Under the optimum conditions, the conversions of mono-alkyl tertiary amines could attain over 99%, while the conversions of di-alkyl tertiary amines reached over 95%. Moreover, a series of quaternary ammonium salts with new counterions (HCO₃, CH₃COO, CH₃CH₂COO, CH₃CH(OH)COO) were synthesized by the hydrolysis of methyl carbonate quaternary ammonium salts or by ion exchange reaction of methyl carbonate quaternary ammonium salts with corresponding acids.     

Methyl formation from methanol decomposition on Pd{111} and Pt{111}

The decomposition of CH₃OH adsorbed on Pd{111} and Pt{111} is compared as the surface is heated between 100 and 500 K. Using secondary ion mass spectrometry (SIMS) and thermal programmed desorption (TPD) it is suggested that an anomalous CH ₃ ⁺ ion signal observed previously by Akhter and White on oxygen precovered Pt{111} arises from the formation of a surface CH₃ species resulting from activation of the C-O bond of CH₃OH. This interpretation stems from a recent observation by Levis, Zhicheng and Winograd that CH₃OH decomposes to CH₃, OH and OCH₃ on clean Pd{111} between 100 and 300 K. The results are discussed in terms of the relative ability of these metals to synthesize CH₃OH from CO and H₂.     

Solution combustion synthesis of α-Al2O3 using urea

The processes involved in the solution combustion synthesis of α-Al₂O₃ using urea as an organic fuel were investigated. The data describing the influence of the relative urea content on the characteristic features of the combustion process, the crystalline structure and the morphology of the aluminium oxide are presented herein. Our data demonstrate that the combustion of stable aluminium nitrate and urea complexes leads to the formation of α-alumina at temperatures of approximately 600–800 °C. Our results, obtained using differential thermal analysis and IR spectroscopy methods, reveal that the low-temperature formation of α-alumina is associated with the thermal decomposition of an α-AlO(OH) intermediate, which was crystallised in the crystal structure of the diaspore.     

Thermal gasification behavior of plastics with flame retardant

In order to develop effective final treatment system of waste plastics, thermal gasification characteristics of plastics compounds containing flame retardant were investigated. Polypropylene (PP) with flame retardant, which was composed by Al(OH)₃ or (NH₄PO₃)_n, was decomposed in an image furnace. Mass reduction during thermal decomposition was measured by an electric micro-balance. The gas components produced by the thermal decomposition were analyzed with a gas analyzer (MEXA 4000 FT, Horiba Ltd.). Soluble organic fraction (SOF) components in a condensable emission during the decomposition process were analyzed with a combustion type PM analyzer (MEXA 1370 PM, Horiba Ltd.). In addition, SOF and solid carbon in the remains after the thermal decomposition were also analyzed by the PM analyzer. The oxygen concentration was changed from 0% to 21% and the content of flame retardant was changed from 0% to 50%. It was found that thermal decomposition temperature increased with a decrease of oxygen concentration. Flame retardant had small effect on the thermal decomposition temperature. However, gas components produced by thermal decomposition were changed corresponding to the containing ratio of flame retardant. The mass of remains was also affected by the ratio of flame retardant. As for the PP with Al(OH)₃, it was considered that PP was completely decomposed and main component of the remains was Al₂O₃ produced by decomposition of Al(OH)₃ even if the surrounding temperature increased up to 900 K. As for the PP with (NH₄PO₃)_n, gradual mass reductions continued after rapid mass reductions. The ratio of SOF and carbon contents in the remains after decomposition of PP with (NH₄PO₃)_n were higher than the case of PP with Al(OH)₃.     

3D supramolecular open-framework constructed by inorganic [B5O6(OH)4]− and organic [CH3COO]− anions

A borate compound [Ni(en)₃][B₅O₆(OH)₄][CH₃COO] (1) has been synthesized under mild hydrothermal conditions. The newly synthesized compound was characterized by single-crystal X-ray diffraction, elemental analysis and thermogravimetry. The three-dimensional (3D) supramolecular open-framework of compound 1 is constructed by inorganic [B₅O₆(OH)₄]⁻ building units and organic [CH₃COO]⁻ anions through hydrogen bonds, and the charge-balancing [Ni(en)₃]^2 + cations are located in 3D channels. It is very interesting that there exist two helical chains formed by [B₅O₆(OH)₄]⁻ building units and organic [CH₃COO]⁻ anions through hydrogen bonds in compound 1 along different axes. Magnetic measurement indicates that compound 1 exhibits paramagnetic behavior down to 4 K.     

Preparation of carboxylic acids from hydroxy compounds by oxidation with ozone

Various mono- and dicarboxylic acids were obtained with appreciable yields from saturated hydroxy compounds by oxidation in aqueous acetic acid with a mixture of ozone and oxygen followed with oxygen. The starting materials and the mono- and dicarboxylic acids obtained were as follows: Primary alcohols RCH₂OH → RCOOH; α,ω-glycols HOCH₂(CH₂)_nCH₂OH → HOOC(CH₂)_nCOOH; secondary alcohols and 12-hydroxyoctadecanoic acid R₁CH₂CH(OH)CH₂R₂ → R₁COOH + R₂CH₂COOH + R₁CH₂COOH + R₂COOH; alicyclic alcohols CH₂(CH₂)_nCHOH → HOOC(CH₂)_nCOOH; 9,10-dihydroxyoctadecanoic acid CH₃(CH₂)₇CH(OH)CH(OH) (CH₂)₇COOH → CH₃(CH₂)₇COOH + HOOC(CH₂)₇COOH. Small amounts of aldehydes, ketones, and carboxylic acids having fewer carbon atoms than those of the carboxylic acids formed as main products were also detected from some of the oxidation products.     

Thermal decomposition of cerium(III) acetate studied with sample-controlled thermogravimetric–mass spectrometry (SCTG—MS)

Thermal decomposition of cerium(III) acetate hydrate, Ce(CH₃CO₂)₃·1.5H₂O, to cerium(IV) oxide, CeO₂, in helium has been successfully investigated by sample-controlled thermogravimetry combined with evolved gas analysis by mass-spectrometry (SCTG–MS). Cerium(III) anhydrous acetate decomposed to cerium (IV) oxide through four decomposition steps in the temperature range of 250–800 °C. SCTG–MS was very useful to distinguish the successive decomposition accompanying the formation of the intermediate products to identify simultaneous gas evolution during the mass losses. The decomposition intermediates quenched from SCTG were characterized by X-ray diffraction (XRD) and X-ray absorption near-edge structure (XANES). The XANES revealed clearly the coexistence of Ce(III) and Ce(IV) and the valence change from cerium(III) to cerium(IV). The three decomposition intermediate products were presumed to be Ce₂O(CH₃CO₂)₄, Ce₂O₂(CH₃CO₂)₂ and Ce₂O₂CO₃. A detailed thermal decomposition mechanism of Ce(CH₃CO₂)₃·1.5H₂O is discussed.     

Preparation and formation mechanism of Al-Si/Al2O3 core-shell structured particles fabricated via steam corrosion

In this study, Al-Si/Al₂O₃ core-shell structured particles were fabricated via pressurized steam corrosion for 1 h followed by heating for 3 h at 1100 °C. After steam corrosion, a layer composed of disordered crystals covered the surfaces of the Al-Si alloy particles. After heating, Al-Si/Al₂O₃ core-shell structured particles with complete shells were prepared. The thickness of the shell was approximately 2 μm, and it enclosed the Al-Si alloy core. The shell exhibited excellent thermal stability because, even at 1100 °C, the mass gain ratio of the encapsulated particle was less than 0.5%. Scalloped patterns of alumina were formed by the oxidation of Al, which was inlaid through and upon the alumina shell. The shell formation mechanism suggested that the α-Al₂O₃ shell resulted from the combination of the decomposition of surface Al(OH)₃ crystals and the oxidation of Al from the core.     

Synthesis and properties of novel liquid ester-free reworkable cycloaliphatic diepoxides for electronic packaging application

Four novel liquid cycloaliphatic diepoxides, with two epoxycyclohexyl moieties linked via -O- (EpoI), -OCH₂CH₂O- (EpoII), -OCH (CH₃)CH₂O- (EpoIII), -OCH(CH₃)CH₂CH(CH₃)O- (EpoIV), respectively, and their diene precursors were synthesized and characterized. These diepoxides could be readily cured with hexahydro-4-methylphthalic anhydride (HMPA) using Iron (III) acetylacetonate as curing accelerator. The thermal and mechanical properties of cured products were examined by differential scanning calorimetry (DSC), thermal mechanical analysis (TMA) and dynamic mechanical analysis (DMA). The thermogravimetric analysis (TGA) data revealed that, the cured EpoI and EpoII had similar thermal decomposition onset temperature to the commercial ERL-4221™ (>300 °C), whereas the cured EopIII and EpoIV, having secondary or tertiary carbon-ether linkages, started to decompose at obviously lower temperature (around 220 °C), which just lay in the desired reworkability temperature range (200-300 °C). The higher glass transition temperature (>120 °C) and moderately low thermal decomposition temperature made EpoIII and EpolV suitable candidates for future reworkable flip chip electronic packaging application.     

Investigation of mechanism of Al(OH)3 crystal growth

Crystallization of Al(OH)₃ that occurs during the decomposition of caustic soda solutions is an important part of Bayer process for alumina production. Several phenomena, which influence the physicochemical characteristics of precipitated Al(OH)₃, occur simultaneously during this process. They are nucleation, agglomeration, and crystal growth of Al(OH)₃. In this article, we have investigated the mechanism of Al(OH)₃ crystal growth from pure caustic soda solutions and in the presence of oxalic acid. The results have shown that the growth of Al(OH)₃ crystals from caustic soda solutions follow the B + S model (birth and spread). New Al(OH)₃ particles, formed during the decomposition process of pure caustic soda solutions, are characterized by regular hexagonal shape. The nuclei have the same geometry as the contact face. However, microstructural investigations of Al(OH)₃ samples, obtained by crystallization from caustic soda solutions in the presence of oxalic acid, have shown the presence of nuclei of irregular shape in addition to regular ones. So, the presence of oxalic acid in the caustic soda solutions leads to a change in crystal habit. Besides, the results obtained by kinetic investigation confirmed the mentioned mechanism of Al(OH)₃ crystal growth.     

氢氧化铝对导热加成型有机硅灌封胶性能的影响

以粘度为300和1 000 mPa·s的端乙烯基硅油复配,含氢硅油为交联剂,三氧化二铝为导热填料,氢氧化铝[Al(OH)_3]为阻燃剂,制备了无卤阻燃导热加成型有机硅灌封胶,研究Al(OH)_3用量对导热加成型有机硅灌封胶性能的影响。结果表明:随着Al(OH)_3用量的增大,加成型有机硅灌封胶的阻燃性能和导热性能提高,粘度增大,体积电阻率和物理性能下降;当Al(OH)_3用量为60份时,加成型有机硅灌封胶的综合性能最佳。     

Metal chelates as synergistic flame retardants for flexible PVC

The thermal degradation of flexible PVC treated with various metal chelates containing Cr, Al, Fe, Co, Ni, Cu, or Zn combined with two compounds, Al(OH)₃ and Mg(OH)₂, was studied by thermal analysis. Limiting Oxygen Index (LOI), Smoke Density Rating (SDR), and mechanical properties were investigated. The structure of the char formed after combustion of the PVC compounds was observed through scanning electron microscopy (SEM). The high LOI and char yield of flexible PVC treated with flame retardants showed that there was a good synergistic effect between Al(OH)₃, Mg(OH)₂, and metal chelates. J. VINYL. ADDIT. TECHNOL., 11:70–75, 2005. © 2005 Society of Plastics Engineers.     

Thermal routes to metal complexed polyimines; facile conversion of CoX2(NH2CH2CH{OEt}2)2 to CoX2{=NCH2CH=}2

Cobalt(II) complexes of the form CoX₂(NH₂CH₂CH{OEt}₂)₂ [X=Cl, Br, I] react hydrolytically in solution to convert hemiacetal moieties to aldehydes, the latter undergoing Schiff base condensation. Complex decomposition and the separation of metal salt and organic material occur concomitantly. In contrast, thermal reactions afford metal complexed polyimines of the form CoX₂{=NCH₂CH=}₂. Analyses are consistent with the liberation of four equivalents of ethanol per mole of CoX₂(NH₂CH₂CH{OEt}₂)₂ via an autocatalytic cycle of hemiacetal hydrolysis and Schiff base condensation. Such thermal routes offer facile access to metal complexed polyimines.     

Surface Base Sites of MgO Covered with Al2O3: XANES Analysis of Al and Mg K-edges

Solid bases comprising MgO covered with Al₂O₃ were prepared by decomposition of Al(OCH(CH₃)₂)₃ over Mg(OH)₂ in ethyl acetate. Catalysts containing more than 10 mol% Al were insoluble in acetone. Aluminum occupied mainly octahedral sites in the low content range; tetrahedral structure being the principal one in the high range.     

The synthesis,using microwave irradiation and characterization of novel,organosoluble metal-free and metallophthalocyanines substituted with flexible crown ether moieties

Cyclotetramerization of a phthalonitrile derivative to the metal-free phthalocyanine was accomplished in n-pentanol in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene at reflux under an argon atmosphere. Ni(II), Zn(II), Co(II), Cu(II) phthalocyanines with four, peripheral 4-[methyleneoxy(12-crown-4)] groups were synthesized from 4-[{(12-crown-4)-yl}methyleneoxy]phthalonitrile in the presence of the anhydrous, divalent metal salts (NiCl₂, Zn(CH₃COO)₂, CoCl₂ and CuCl₂). The green phthalocyanines were soluble in common organic solvents such as CHCl₃, CH₂Cl₂, CH₃COCH₃, THF, DMF and DMSO. The structures of the target compounds were confirmed using elemental analysis, IR, ¹H NMR, ¹³C NMR, UV–vis and MS spectral data.     

Characterization of products of interaction between kaolin ore and ammonium sulphate

The reaction products resulting from the interaction between kaolin ore and ammonium sulphate depend on molar ratios between reactants, reaction temperature and time of interaction. The reaction products were characterized by means of XRD. They were composed of silica, unreacted kaolin ore, traces of iron, magnesium, calcium, titanium and NH₄Al(SO₄)₂ and (NH₄)₃Al(SO₄)₃. The last compound was produced alone at 553 K, whereas mixtures of them were produced between 553 and 823 K after a short time of interaction (0.5 h). On other hand the former compound was produced alone after longer heating (c. 2 h). At 823 K, a mixture composed of Al₂(SO₄) and NH₄Al(SO₄)₂ was identified after 0.5 h, whereas anhydrous aluminium sulphate was detected alone after heating the reaction mixture for 2 h. The transformation of (NH₄)₃Al(SO₄)₃ into NH₄Al(SO₄)₃ and alumina leads to a decrease in the percentages of extracted alumina from kaolin ore at relatively higher temperatures and/or longer heating of reaction mixtures. The investigation was also devoted to establishing the possible reactions which lead to the formation of Fe₂O₃, MgO, CaO and TiO₂ as soluble salts together with aluminium compounds. The percentages of their extraction are low compared with the original quantities found in kaolin ore. From the obtained results, both Al₂(SO₄)₃ and NH₄Al(SO₄)₂ can be prepared from local kaolin with a reasonable degree of purity which makes it possible to produce them for use for different industrial and pharmaceutical purposes.     

Layered double hydroxide/NaSb(OH)6–poly(vinyl chloride) nanocomposites: Preparation,characterization, and thermal stability

A novel layered double hydroxide/NaSb(OH)₆‐based nanocomposite (Sb‐LDH) has been prepared via intercalation of thio‐antimonite (SbS₃^3?) and reconstruction of LDH using Mg‐Al LDH as precursors. It is composed of LDH nanolayers with thickness of 25 nm and NaSb(OH)₆ nanoparticles with diameter of 3–25 nm. The presence of NaSb(OH)₆ will decrease the decomposition intensity and hinder the decomposition of Mg‐Al LDH because of the potential synergetic effect. When applied to poly(vinyl chloride) (PVC) composites, both Mg‐Al LDH and Sb‐LDH can enhance the thermal stability and increase the decomposition temperature of PVC. Compared with Mg‐Al LDH, Sb‐LDH results in higher decomposition temperatures and whiteness and higher initial and long‐term stabilities due to the presence of NaSb(OH)₆, which can react with HCl and coordinate with Cl in the PVC chains. Because Mg‐Al LDH will accelerate the dehydrochlorination of PVC driving by the Lewis acid such as AlCl₃, the thermal stability of PVC decreases with increasing nanofiller loading. When 1 wt % Sb‐LDH was added, the color change time and Congo red time of PVC composites are 140 min and 154 min, respectively. With enhanced thermal stabilization, this novel LDH nanocomposite could gain promising application in thermal stabilizer for PVC resins. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Basic magnesium carbonate flame retardants for polypropylene

Magnesium hydroxide and magnesium carbonates have attracted attention as endothermic flame retardants that are sufficiently stable to be incorporated into thermoplastics without decomposition. In this survey, a basic form of magnesium carbonate, magnesium carbonate hydroxide pentahydrate [(MgCO₃)₄ · Mg(OH)₂ · 5H₂O] was evaluated as a flame retardant for polypropylene. This filler (MCHP) has a thermal stability intermediate between that of alumina trihydrate (ATH) and magnesium hydroxide, which is sufficient to allow incorporation into polypropylene without decomposition. The MCHP is most effective at high filler concentrations near 60% where it was found to impart a Limiting Oxygen Index of 28.2 with a V-O rating (no dripping). This is slightly more effective than the flammability ratings for ATH and Mg(OH)₂ under the same conditions. The effectiveness of MCHP was attributed to the large endothermic loss of water of hydration, which also dilutes the combustion gases. This action was further aided by the formation of an intumescent char on the burning surface, which eventually extinguished the flame. Various combinations of magnesium oxide, magnesium hydroxide, magnesium carbonate, and MCHP were evaluated in order to clarify the mechanism of the flame retardant and improve the efficiency of the protective action. However, no synergism was evident, and the flame retardant results were found to be additive. The mechanical properties and processabilities of these highly filled compounds are very sensitive to the type of surface treatment. The method of Savides was employed to compare the burning temperature of the test specimens and to measure the rates of combustion.     

Synthesis of AlN powder from Al(OH)3 by reduction–nitridation in a mixture of NH3–C3H8 gas

Aluminum nitride (AlN) powders were synthesized by gas-reduction–nitridation of aluminum hydroxide (Al(OH)₃) powders using a mixture of NH₃ and C₃H₈ gases. A high conversion to AlN (over 70% of naitridation ratio) and single-phase AlN were achieved over 1200 °C. The specific surface area of the products decreased with increasing of reaction temperature and soaking time, and products obtained contain much lesser oxygen than those of the previous researches. The reason why such nanosized AlN powders were easily obtained from Al(OH)₃ was considered to be the higher surface areas of transition alumina formed by dehydration of Al(OH)₃ during firing.