The Effect of Additives on the Burning Rate of Silicon‐Calcium Sulfate Pyrotechnic Delay Compositions

The effect of fuel particle size as well as the influence of inert and reactive additives on the burning rate of the Si‐CaSO₄ composition was evaluated. The burning rate decreased with increase in fuel particle size, while the enthalpy remained constant. Addition of fuels to the base composition increased the burning rate, with an increase from 12.5 mm ⋅ s⁻¹ to 43 mm ⋅ s⁻¹ being recorded upon 10 wt‐% Al addition. Ternary mixtures of silicon, calcium sulfate, and an additional oxidizer generally decreased the burning rate, with the exception of bismuth trioxide, where it increased. The Si‐CaSO₄ formulation was found to be sensitive to the presence of inert material, addition of as little as 1 wt‐% fumed silica stifled combustion in the aluminum tubes.     

Development and Performance of Boron Carbide‐Based Smoke Compositions

Pyrotechnic smoke compositions for visual obscuration containing boron carbide, potassium nitrate, potassium chloride, and various lubricants are described. Only the waxy lubricants stearic acid and calcium stearate slowed the burning rate into a range suitable for end‐burning smoke grenades. For compositions pressed into steel cans, the addition of just 2 wt‐% calcium stearate was shown to reduce the burning rate from 0.50 cm s⁻¹ to 0.09 cm s⁻¹. In this system, potassium chloride serves as a diluent that reduces incandesence but also increases slag formation. Compositions containing potassium chloride in the 25–30 wt‐% range exhibited both acceptably low incandescense and slag formation upon burning, while also producing copious amounts of white smoke. These experimental compositions were loaded into full‐size grenade cans; field and smoke chamber testing revealed that they outperform the US Army’s in‐service M83 TA grenade both qualitatively and quantitatively. The photopic mass‐based figures of merit for experimental grenades KCl‐25, KCl‐30, and a production‐run M83 TA grenade were 2.51, 2.19, and 1.44 m² g⁻¹, respectively.     

Mn+Sb2O3 Thermite/Intermetallic Delay Compositions

The binary Mn+Sb₂O₃ pyrotechnic composition was investigated for mining detonator time delay applications. EKVI thermodynamic modelling predicted two maxima in the adiabatic reaction temperature. The local maximum, at a manganese fuel content of ca. 36 wt‐%, corresponds to a pure thermite‐type redox reaction: 3 Mn+Sb₂O₃→3 MnO+2Sb. The overall maximum in the adiabatic reaction temperature (ca. 1640 K), at the fuel‐rich composition of 49 wt‐% Mn, is consistent with the reaction 5 Mn+Sb₂O₃→3 MnO+2 MnSb, i.e. a combination of the standard thermite with an additional exothermic intermetallic reaction. XRD analysis of combustion residues confirmed the formation of MnSb and Mn₂Sb for fuel‐rich compositions. Burn rates were measured using delay elements assembled into commercial detonators. The d₅₀ particle sizes were 23.4 and 0.92 μm for the Mn fuel and Sb₂O₃ oxidant powders, respectively. The delay elements comprised rolled lead tubes with a length of 44 mm and an outer diameter of 6.4 mm. The rolling action compacted the pyrotechnic compositions to 74 ± 2 % theoretical maximum density. The burning rate increased linearly from 4.2 to 9.4 mm s⁻¹ over the composition range 25–50 wt‐% Mn.     

Development and Performance of the W/Sb2O3/KIO4/Lubricant Pyrotechnic Delay in the US Army Hand‐Held Signal

Gassy pyrotechnic delays composed of tungsten, antimony(III) oxide, potassium periodate, and various lubricants have been developed for use in the US Army hand‐held signal. The new compositions were developed to replace the current formulation, which contains potassium perchlorate and barium chromate, chemicals that are facing increasing scrutiny due to environmental regulation. The hand‐held signal delay housing was used to demonstrate the burning rate tunability of the new compositions. The addition of 1–5 % of waxy lubricants (stearic acid or calcium stearate) was found to have a profound effect on burning rate. The effect of tungsten content and the Sb₂O₃/KIO₄ ratio on burning rate was also probed. A wide range of inverse burning rates (2 to 15 s cm⁻¹) were demonstrated, which encompasses the 7 to 8.5 s cm⁻¹ range required by the hand‐held signal. The W/KIO₄ reaction produces I₂, which was observed by visible spectroscopy in the vapor above a sample of combustion residue.     

Measurement and Modelling of Pyrotechnic Time Delay Burning Rates: Application and Prediction of a Fast Burning Delay Composition

A predictive numerical model was implemented for a time delay based on the Si+Pb₃O₄ system. The reaction kinetic parameters were estimated by comparing predicted surface temperature profiles with experimental data acquired with an infrared camera. Fair agreement between the modelled and measured burning rates was achieved. The burning rate is predicted to increase by 9.4 % for every 50 °C increase in ambient temperature. The core diameter was found to have a slightly larger impact on the burning rate than the wall thickness. The effect of using different wall thickness materials was evaluated and indicated that the burning rate is significantly influenced by the wall material when the thermal conductivity is increased and the volumetric heat capacity is reduced. The shape of the combustion front was found to widen with a long tail for materials with a low thermal conductivity and a narrower combustion front with a short tail for materials with high thermal conductivity. Preheating occurred for pyrolytic graphite‐ and diamond‐based elements but no radial combustion was observed. The external heat transfer parameters (convection and radiation) did not affect the burning rate of the fast delay composition. It is concluded that the ambient temperature, volume fraction solids, molar heat of reaction, core and outer diameter are the factors that most significantly influence the burning rate of the Si+Pb₃O₄ composition in long cylindrical elements.     

Synthesis of PS‐g‐POSS hybrid graft copolymer by click coupling via ”graft onto” strategy

Polystyrene (PS)‐incorporated polyhedral oligomeric silsesquioxanes (POSS) organic–inorganic hybrid graft copolymer could be achieved by click coupling reaction between alkyne groups in POSS and azido groups in PS via “graft onto” strategy. Alkyne‐functionalized POSS was synthesized via thiol‐ene facile click reaction and subsequent amidation reaction with very high yield. Azido‐multifunctionalized PS could be synthesized by chloromethylation and subsequent azido reaction. The chemical structures of PS‐(CH₂Cl)_m, PS‐(CH₂N₃)_m, and PS‐g‐POSS were determined by Fourier transform infrared and ¹H NMR characterization. PS‐g‐POSS presented a better hydrophobic property with contact angle of 113° than that of PS (85°). And PS‐g‐POSS with ≤5% of grafting degree had lower glass transition temperature (T_g) than that of PS and then it increased up to 112°C with grafting degree. An obvious aggregation of POSS phase with 10–80 nm in size was formed in PS‐g‐POSS matrix. In addition, 5 wt % of PS‐g‐POSS was added to general purpose polystyrene (GPPS) to remarkably improve its tensile strength from 45 to 57 MPa. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Sb6O13 and Bi2O3 as Oxidants for Si in Pyrotechnic Time Delay Compositions

Lead and its compounds in detonator time delays are being phased out owing to environmental and health concerns. It was found that changing from the conventional rolled lead elements to rigid aluminium tubes caused a significant decrease in the burn rate. It also impaired ignitability, especially of slow burning compositions such as Si BaSO₄. Consequently, potential alternatives for the latter and also the fast burning Si Pb₃O₄ system were sought. Bi₂O₃, prepared by thermal decomposition of bismuth subcarbonate, gave fast burning compositions with silicon as fuel (155 mm s⁻¹ with 20% Si). This system was ignitable by the spit of a shock tube. The Si Sb₆O₁₃ system required an initiating composition and yielded slow burning compositions. The lowest sustainable and reproducible burn rate in lead tubes, in the absence of additives, was 4.8 mm s⁻¹. In lead tubes, it was possible to reduce the burn rate further by adding fumed silica: A composition obtained by adding 10% fumed silica (add‐on basis) to a 10% Si–90% Sb₆O₁₃ composition still burned reliably at a burn rate of 2.3 mm s⁻¹.     

Synthesis,characterization, and thermo mechanical properties of siloxane‐modified epoxy‐based nano composite

In this study, polymer hybrid composites were synthesized by sol‐gel process. 3‐Amino‐propyltrimethoxysilane [APTMS)/γ‐Glycidoxypropyl trimethoxy‐silane (GPTMS); (4, 4′‐Methylene‐dianiline (DDM)] and 1,4‐Bis(trimethoxysilylethyl) benzene (BTB) were added to DGEBA type epoxy resin for anticipated to exhibit excellent thermal stability. Boron trifluoride monoethylamine (BF₃MEA) was used as catalyst. The structure of nanocomposites was characterized by attenuated total reflectance (ATR) and solid‐state ²⁹Si NMR which suggest EP‐APTMS‐BTB/EP‐GPTMS‐BTB possesses T³; T¹–T⁰, and T¹ structures when the BTB content was lower than 10 wt % and higher 20 wt %, respectively. BF₃MEA was proved to be an effective catalyst for the sol‐gel reaction of APTMS, but it could not promote for GPTMS. From TEM microphotographs, EP‐APTMS‐BTB (10 wt %) possesses a dense inorganic structure (particle size around 5–15 nm) compare with the loose inorganic structure of EP‐GPTM‐/BTB (10 wt %). DSC, TGA were use to analyze the thermal properties of the nanocomposites and DMA was used to analyze the dynamic mechanical properties of hybrid composites. The T_gs of all nanocomposites decreased with the increasing BTB content. A system with BTB content lower than 10 wt % showed good dynamic mechanical property and thermal stability (Td₅ increased from 336°C to 371°C, char yield increased from 27.4 to 30.2%). The structure of inorganic network affects the Td₅ and dynamic mechanical properties of composite. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40984.     

Metal Fluorocarbon Pyrolants,XVI : Theoretical and Experimental Investigation of Poly[bis(2,2,2‐trifluoroethoxy)phosphazene] (PTFEP) as Oxidizer in Magnesium Based Pyrolants

Consolidated magnesium/poly[bis(2,2,2‐trifluoroethoxy)phosphazene] (MPZ) pyrolants display a stable combustion regime between ξ(Mg) 30–83 wt‐%. The combustion rate increases with increasing magnesium content. Mixtures containing between 15–29 wt‐% Mg do ignite with a butane torch but extinguish rapidly thereafter. The combustion flames for each stoichiometric range exhibit particular features such as luminous carbon particles, after burn luminescence of Mg and burning Mg‐rich ejecta. UV/Vis spectra of the combustion flames show a distinct continuum superimposed from signals for transient CF₂, Mg, MgF, MgO, P₂⁺, PH, PN, and PO. The thermochemical calculation using NASA‐CEA indicate the highest adiabatic temperatures 1889 K at ξ(Mg)=35 wt‐%. The aerobic combustion of MPZ yields similar temperatures as common magnesium/polytetrafluoroethylene pyrolants.     

Measurement and Modelling of Pyrotechnic Time Delay Burning Rates: Method and Model Development

The burning rates of a slow reacting Mn+Sb₂O₃ and a fast reacting Si+Pb₃O₄ time delay composition, filled into lead tubes, were measured with an infrared camera, with two thermocouples and in the form of a fully assembled detonator. The infrared camera method returned values that were on average about 12 % lower than those recorded for the detonators. The temperature profiles measured for the slow burning elements were fully developed, whereas those obtained for the fast burning Si+Pb₃O₄ elements were not. A numerical model was developed to simulate the Mn+Sb₂O₃ system. Kinetic parameters were determined by least square fits to the recorded surface temperature profiles. The model made it possible to determine the effect of various property variations on the burning rate. The thermal conductivity of the delay composition was found to have the smallest impact and the heat of reaction the largest effect.     

Investigation of the Burning Properties of Slow‐Propagation Tungsten Type Delay Compositions

Twenty‐eight delay compositions with a variation of the W content of ±20% wt, on the basis of the primitive formula, W/BaCrO₄/KClO₄/SiO₂/Viton=27 : 54 : 11 : 6 : 2, were designed for delay ignition in self‐destruction application of fuse. They were processed finally to be cylindrical pellets and were then characterized by measuring their burning properties including igniting ability, burning rate, and output flame temperature. In the experiments, the cylindrical pellets were packed into a heat‐resisting quartz tube and were ignited by an electrical‐heating wire. A high‐speed video camera and a digital‐image processing device were used for simultaneously recording the combustion phenomena such as ignition and flame propagation. In addition, the output flame temperature was detected by placing a thermocouple at the end of the quartz tube. The delay compositions were also loaded in a cylindrical aluminum tube to measure burning properties as compared to naked cylindrical pellets. According to these experimental results, this work discussed the effect of composition on burning properties. The consequences of these analyses will be very important and useful for defining criteria in formulating the tungsten type slow‐propagation delay compositions, as well as for improving self‐destruction designs of fuse.     

Synthesis of a melamine‐cyclotriphosphazene derivative and its application as flame retardant on cotton gauze

The halogen‐free flame retardance of natural fiber is an everlasting challenge due to the well‐known poor solubility of phosphazene in water. In this case, a new cyclotriphosphazene derivative (MCP) was synthesized. It was etherized hexamethylolmelamine (HMMM) and hexachloro‐cyclotriphosphazene (HCCP) by one pot reaction. It was characterized by ¹H NMR, ¹³C NMR, ³¹P NMR, FT‐IR, TGA, SEM, limited oxygen index (LOI) and vertical flame testing. The MCP has good solubility in water and thermosetting MCP has compact structure which can expand several times after burning. Cotton gauze was soaked in six different concentration of aqueous solutions of MCP (0 wt %, 5 wt %, 10 wt %, 15 wt %, 20 wt % and 25 wt %, respectively) to obtain the flame retardant cloth. The cloth was soaked in 20 wt % MCP solution had higher char yield and LOI. They had no any afterflame and afterglow, and gauze 2‐ gauze 5 cannot be burned out in 12s ignition time. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43555.     

Synergistic effect between silicone‐containing macromolecular charring agent and ammonium polyphosphate in flame retardant polypropylene

A novel silicone‐containing macromolecular charring agent (Si‐MCA) was synthesized via polycondensation, and it was combined with ammonium polyphosphate (APP) to flame retard polypropylene (PP). The results showed that Si‐MCA exhibited a good synergistic effect with APP in flame retardant PP. When the content of APP was 18.7 wt % and Si‐MCA was 6.3 wt %, the limiting oxygen index value of the PP/APP/Si‐MCA composite was 33.5%, and the vertical burning (UL 94) test classed a V‐0 rating. The peak heat release rate, total heat release, average mass loss rate, and total smoke production of the composite were also decreased significantly. Moreover, the PP/APP/Si‐MCA composite showed an outstanding water resistance. After soaking in 70°C water for 168 h, the PP/APP/Si‐MCA composite could still reach a UL 94 V‐0 rating at 20.0 wt % IFR loading, whereas the PP/APP/PER composite failed to pass the UL 94 test even at 25.0 wt % IFR loading. Thermogravimetric analysis, thermogravimetry‐Fourier transform infrared spectrometry, and scanning electron microscopy‐energy dispersive X‐ray spectrometry results revealed that a compact and thermostable intumescent char was formed by APP/Si‐MCA during burning, thus effectively improved the flame retardancy of PP. The possible synergistic mechanism between APP and Si‐MCA was also discussed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41580.     

Preparation of diacylglycerol‐enriched palm olein by phospholipase A1‐catalyzed partial hydrolysis

Partial hydrolysis of palm olein catalyzed by phospholipase A₁ (Lecitase Ultra) in a solvent‐free system was carried out to produce diacylglycerol (DAG)‐enriched palm olein (DEPO). Four reaction parameters, namely, reaction time (2–10 h), water content (20–60 wt‐% of the oil mass), enzyme load (10–50 U/g of the oil mass), and reaction temperature (30–60 °C), were investigated. The optimal conditions for partial hydrolysis of palm olein catalyzed by Lecitase Ultra were obtained by an orthogonal experiment as follows: 45 °C reaction temperature, 44 wt‐% water content, 8 h reaction time, and an enzyme load of 34 U/g. The upper oil layer of the reaction mixture with an acid value of 54.26 ± 0.86 mg KOH/g was first molecularly distilled at 150 °C to yield a DEPO with 35.51 wt‐% of DAG. The DEPO was distilled again at 250 °C to obtain a DAG oil with 74.52 wt‐% of DAG. The composition of the acylglycerols of palm olein and the DEPO were analyzed and identified by high‐performance liquid chromatography (HPLC) and HPLC/electrospray ionization/mass spectrometry. The released fatty acids from the partial hydrolysis of palm olein catalyzed by phospholipase A₁ showed a higher saturated fatty acid content than that of the raw material.     

Important Parameters of Epoxidation of 1,4‐bis(allyloxy)butane in Aqueous‐Organic Phase Transfer Catalytic System

The epoxidation of 1,4‐bis(allyloxy)butane to give 1‐allyloxy‐4‐glycidoloxybutane and 1,4‐bis(glycidoloxy)butane was investigated. The reaction was carried out with 30 wt % hydrogen peroxide under phase transfer catalysis (PTC) conditions in the presence of sodium tungstate(VI) dihydrate and orthophosphoric(V) acid (WO₄^2–/PO₄^3–). Methyltrioctylammonium chloride (Aliquat 336) was used as the phase transfer catalyst. The effect of agitation speed and reaction temperature on the yield of epoxidation products was determined.     

“Metakaolin‐Slag‐Clinker Blends.” The Role of Na+ or K+ as Alkaline Activators of Theses Ternary Blends

This article reports on research into the use of solid alkalis (Na₂CO₃ and K₂CO₃) as activators to obtain hybrid cement (cement whose hydration generates a mix of C–A–S–H and (N,C)–A–S–H gels) from a blend of 20% clínker + 40% blast furnace slag + 40% metakaolin. More specifically, the study aimed to determine the effect of activator dosage (5 and 8 wt%) and type of alkaline cation (Na⁺ or K⁺) on the 2‐ and 28‐d mechanical strength of the end materials. The findings showed that the highest mechanical strength values were obtained with 5% Na₂CO₃. According to the XRD, NMR, and SEM/EDX analyses conducted on the reaction products, the alkalinity and solubilized chemical species generated by adding 5% Na₂CO₃ to the system yielded a mix of (N,C)–A–S–H and C–A–S–H cementitious gels as the main reaction products. The secondary reaction products included metastable (3CaO·Al₂O₃·CaCO₃·11H₂O‐type) carboaluminates that evolved into the calcite or vaterite forms of calcium carbonate. When K₂CO₃ was used (instead of Na₂CO₃), a (3CaO·Al₂O₃·0.5Ca(OH)₂·0.5CaCO₃·11H₂O‐type) hemicarboaluminate also formed. The study also revealed that Na⁺ favors coagulation/precipitation more effectively than K⁺, generating gels with a wider range of Qⁿ species.     

Preceramic polymer as precursor for near‐stoichiometric silicon carbon with high ceramic yield

Precursor polycarbosilane containing acetylenic and Si? H group (PCAS) has been successfully prepared by the reaction of dilithioacetylene with methyl dichlorosilane, and characterized by gel permeation chromatography, Fourier transform infrared spectroscopy, ¹H‐NMR, ¹³C‐NMR, and ²⁹Si‐NMR. Thermogravimetric analysis curve in nitrogen showed the temperature of 5 wt % weight losses (T_d5) was 613°C, while the ceramic yield of PCAS was 88% at 1000°C. Pyrolysis behavior and structure evolution of the cured PCAS were studied by means of X‐ray diffraction, Raman, scanning electron microscope‐energy dispersive X‐ray spectrometer, transmission electron microscope (selected area electron diffraction and high resolution transmission electron microscope), and elemental analysis. The polymer to ceramic conversion was completed at 1600°C and the results revealed that the ceramic consisted of β‐SiC and α‐SiC. The composition of the ceramic was near‐stoichiometric with molar ratio of Si/C (1.02 : 1) except rare and localized free carbon inclusions. The SiC ceramics exhibited high thermo‐oxidation resistance at elevated temperatures in air atmosphere. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41335.     

Calcium carbonate and ammonium polyphosphate‐based flame retardant composition for polypropylene

The chemical mode of action as a flame retardant of calcium carbonate nanoparticles combined with ammonium polyphosphate in polypropylene was investigated. Reduction in burning rates for 0.5 mm thick samples were observed without appreciable char formation up to 30 wt % loading of additives. Thermogravimetric analysis (TGA) of the mixture of CaCO₃ and ammonium polyphosphate (APP) showed that calcium carbonate nanoparticles react with ammonium polyphosphate before the degradation of the phosphate chains. TGA–FTIR studies of the polymer composite samples and powder mixtures of the additives confirmed the evolution of ammonia and carbon dioxide due to interaction between the additives. X‐ray diffraction (XRD) analysis of chars, obtained after burning the films, showed definite diffraction peaks corresponding to that of calcium metaphosphate. The inert gasses produced by the interaction of the additives hindered the advancing flame and, thus, reduces the burning rates, at times even without char formation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Co‐synthesis of Sm0.5Sr0.5CoO3‐Sm0.2Ce0.8O1.9 Composite Cathode with Enhanced Electrochemical Property for Intermediate Temperature SOFCs

A 70 wt.% Sm_0.5Sr_0.5CoO₃ – 30 wt.% Sm_0.2Ce_0.8O_1.9 (SSC–SDC73) composite cathode was co‐synthesized by a facile one‐step sol–gel method, which showed lower polarization resistance and overpotential than those of physically mixed SSC–SDC73 cathode. The polarization resistance of co‐synthesized SSC–SDC73 cathode at 800 °C was as low as 0.03 Ω cm² in air. Scanning electron microscopy (SEM) images showed that the enhanced electrochemical property was mainly attributed to the smaller grains and good dispersion of SSC and SDC phases within the composite cathode, leading to an increase in three‐phase boundary length. The dependence of polarization resistance with oxygen partial pressure indicated that the rate‐limiting step for oxygen reduction reaction was the dissociation of molecular oxygen to atomic oxygen process. An anode supported fuel cell with a co‐synthesized SSC–SDC73 cathode exhibited a peak power density of 924 mW cm⁻² at 800 °C. Our results suggested that co‐synthesized composite was a promising cathode for intermediate temperature solid oxide fuel cells (IT‐SOFCs).     

Production of bio‐crude from forestry waste by hydro‐liquefaction in sub‐/super‐critical methanol

Hydro‐liquefaction of a woody biomass (birch powder) in sub‐/super‐critical methanol without and with catalysts was investigated with an autoclave reactor at temperatures of 473–673 K and an initial pressure of hydrogen varying from 2.0 to 10.0 MPa. The liquid products were separated into water soluble oil and heavy oil (as bio‐crude) by extraction with water and acetone. Without catalyst, the yields of heavy oil and water soluble oil were in the ranges of 2.4–25.5 wt % and 1.2–17.0 wt %, respectively, depending strongly on reaction temperature, reaction time, and initial pressure of hydrogen. The optimum temperature for the production of heavy oil and water soluble oil was found to be at around 623 K, whereas a longer residence time and a lower initial H₂ pressure were found to be favorite conditions for the oil production. Addition of a basic catalyst, such as NaOH, K₂CO₃, and Rb₂CO₃, could significantly promote biomass conversion and increase yields of oily products in the treatments at temperatures less than 573 K. The yield of heavy oil attained about 30 wt % for the liquefaction operation in the presence of 5 wt % Rb₂CO₃ at 573 K and 2 MPa of H₂ for 60 min. The obtained heavy oil products consisted of a high concentration of phenol derivatives, esters, and benzene derivatives, and they also contained a higher concentration of carbon, a much lower concentration of oxygen, and a significantly increased heating value (>30 MJ/kg) when compared with the raw woody biomass. © 2009 American Institute of Chemical Engineers AIChE J, 2009