High resistance to thermal decomposition in brown cotton is linked to tannins and sodium content

Brown cotton fibers (SA-1 and MC-BL) studied were inferior to a white cotton fiber (Sure-Grow 747) in fiber quality, i.e., a shorter length, fewer twists, and lower crystallinity, but showed superior thermal resistance in thermogravimetric, differential thermogravimetric, and microscale combustion calorimetric (MCC) analyses. Brown cotton fibers yielded 11–23 % smaller total heat release and 20–40 % greater char. Washing fibers in water and a 1 % NaOH solution showed that rich natural inorganic components and the condensed tannins present in brown cotton are responsible for the unusual thermal property. The loss of inorganics from white cotton during a water wash increased the thermal decomposition temperature of cellulose, resulting in no char yield. However, the stronger binding of metal ions for brown cotton as well as its dominant adsorption of sodium ions after a 1 % NaOH wash facilitated the low-temperature thermal-reaction route; the sodium content showed a significant negative correlation with the heat release capacity of the fiber. Condensed tannins greatly enhanced the adsorption of sodium ions to the fiber and exhibited inherent thermal stability. The limiting oxygen indices (LOI) calculated from the MCC parameters indicated the slower burning characteristic of brown cotton, and its LOI was further increased upon adsorption of sodium ions.     

Structure and thermal properties of natural colored cottons and bombax cotton

Chemical compositions, crystalline structures and thermal properties of bombax cotton and natural colored cottons including laurel green, bottle green and brown cotton were investigated by chemical analysis, SEM, IR spectra and X-ray diffraction. The results showed that the crystallinity and crystallite sizes of laurel green cotton were lower than those of bottle green cotton because of the excess content of suberin in the former. The crystallinity of brown cotton was similar to that of white cotton, and bombax cotton had the lowest crystallinity but its crystallite orientation was the highest. Thermal property of bottle green cotton was the most stable, whose decomposition temperature was higher of 30°C than that of common white cotton because of its higher lignin content, and bombax cotton had the lowest thermal degradation temperature. But bottle green cotton reached the highest decomposition speed and made decomposition finish within a very short time, and bombax cotton was just the reverse.     

Distribution of natural radioactivity in coal and combustion residues of thermal power plants

In India about 70 % of the total power generation originates from thermal power plants. Increasing demands of power in a developing country like India has resulted in rapid increase in thermal generation capacity. Coal fired power generation results in huge amounts of fly ash and bottom ash of varying properties. Coal which contains the naturally occurring radionuclides, on burning results in enrichment of these radionuclides in the ashes. Despite the implementation of best possible mechanisms to restrict release of fly ash from the stack, huge amounts of the same gets released in the environment. Fly ash samples from and around six coal-fired power station across India were measured for ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K activity by an HPGe γ-ray spectrometer. Radium equivalent activity and external hazard index were calculated to assess the radiation hazards arising due to fly ash.     

Reduced curing kinetic energy and enhanced thermal resistance of phthalonitrile resins modified with inorganic particles

The effects of inorganic particles such as Al₂O₃ and B₄C on the solidification kinetics and heat resistance of phthalonitrile resin were investigated. The properties of the blends and the cured products were tested by rheometer, differential scanning calorimetry, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The results revealed that B₄C and Al₂O₃ inorganic particles could prolong the gel time of phthalonitrile resin and broaden the processing window. The curing kinetic analysis showed that the presence of the particles could significantly reduce the curing activation energy of phthalonitrile resins by 72.38 kJ/mol down to 43.03 kJ/mol. Meanwhile, the heat resistance of the phthalonitrile resin was improved. Among them, the blend system combined with 30% B₄C showed prominent thermoresistance. And while the T_d5% weight loss temperature was 600°C, char yield at 1000°C was higher than 86% under nitrogen atmosphere; while the T_d5% weight loss temperature was 581°C, char yield at 1000°C was higher than 80% under air atmosphere. Hence, the resulting resins were good candidate matrix of high‐temperature structural composites.     

Enhanced interfacial adhesion,mechanical, and thermal properties of natural flour-filled biodegradable polymer bio-composites

This study examined the interfacial adhesion, mechanical, and thermal properties of compatibilizing agent-treated and non-treated biocomposites as a function of the type of compatibilizing agent. The tensile strength, interfacial adhesion, and heat deflection temperature (HDT) of maleic anhydride-grafted poly(butylene succinate) (PBS-MA) and maleic anhydride-grafted poly(lactic acid) (PLA-MA)-treated biocomposites are greater than those of untreated maleic anhydride-grafted poly(styrene-b-ethylene-co-butylene-b-styrene) triblock copolymer (SEBS-MA) and maleic anhydride-grafted polypropylene (MAPP)-treated biocomposites. The storage modulus (E′) values and the tan δ_max temperatures (T _g) of PBS-MA and PLA-MA-treated biocomposites were slightly higher than that of the untreated biocomposites.     

The application of thermal analysis to the combustion of cellulose

It is shown that the use of differential thermal analysis (DTA) to follow the pyrolysis of cellulose in air products two and sometimes three exothermic peaks. The first peak is associated with the combustion of volatile material, released in the degradation process, the second is caused by the glowing combustion of the carbonaceous residue, and the final exotherm is probably due to the combustion of product gases.The thermogravimetric analysis (TG) data in air show a preliminary loss of water followed by a mass loss of about 85% due to the production of the combustible volatiles. This second step appears identical to the degradation process in nitrogen, but in air the degradation products ignite to produce the first exothermic peak on the DTA. The glowing combustion DTA peak is associated with a further mass loss of about 15% on the TG plot. The use of a thermomechanical analyser shows that a small shrinkage of 3% occurs between 45 and 110°C, with the major collapse taking place between 300 and 370°C. There is, however, an expansion of 10% between 370 and 405°C, believed to be due to a crosslinking reaction.     

Controlled site modification of inorganic networks in hybrid photocurable resins for high thermal crack resistance

For functional hybrid materials with desirable physical properties as well as chemical characteristics, controlled modification, i.e., site selective modification, of inorganic networks is one of the promising approaches. Here, we report a selective modification of less-condensed Si atoms in a siloxane-based UV-cured resin can drastically improve thermal crack resistance. The highly improved thermal crack resistance is attained by elimination of monomeric Si alkoxides using trimethylchlorosilane (TMCS) as a modifier. Liquid- and solid-state ²⁹Si NMR analyses were performed to evaluate the selectivity of reaction between TMCS and monomeric Si alkoxides included in photocurable precursory sols, whereas thermal mechanical analysis was to estimate coefficients of thermal expansion and deformation temperature of the UV-cured resins. The reaction between TMCS and the UV curable precursory sol occurs via a moisture-assisted process involving moderate hydrolysis reactions. As a result, the addition of TMCS increases a temperature at which crack forms from 150 up to 300 °C.     

Simultaneous photolysis of directly linked porphyrin-diazonium salt molecule

Meso-tetra-(p-diazoniumphenyl) porphyrin (TDSPP) can be photolyzed only under anaerobic conditions with a yield of 0.18 during simultaneous irradiation with He-Ne laser light (632.8 nm) and light of the 313 nm line of 0 mercury lamp. The excited singlet state of TDSPP is quenched by externalp-methoxybenzene diazoniumtetra fluoroborate (MeODS) with a rate constant of 9.7 × 10⁹M⁻¹s⁻¹. TDSPP and MeODS interact in the ground state with an equilibrium constant of about 16M⁻¹ and form a fluorescent but photochemically inactive.     

Solid-state thermal amorphization of inorganic polymers

Inorganíc polymers such as silicates, borates and phosphates can be transformed into amorphous solids by heating to an appropriate temperature. Thermal amorphization can be obtained by: 1. thermal dissociation of a crystalline compound, 2. distortion of the crystal structure of a solid during prolonged heat treatment, without change of its chemical composition. The specificity of the materials received, the crystallochemical conditions necessary for the amorphization which takes place, and the high-temperature processes of internal structure reconstitution and recrystallization in the amorphous products are considered. Dedicated to Professor Lisa Heller-Kallai on the occasion of her 65^th birthday     

Solubility of radioactive inorganic salt in supercritical water

Journal of Radioanalytical and Nuclear Chemistry - In order to reduce the deposition of inorganic salt in continuous reactor during the treatment of radioactive spent extraction solvent by...     

Antibacterial cotton treated with N-halamine and quaternary ammonium salt

Quaternary ammonium salts and N-halamines are widely used as biocides in antimicrobial coatings, and have been extensively studied over the past two decades. In this work, 5,5-dimethyl-3-(3′-triethoxysilylpropyl)hydantoin (SPH), and 3-(trimethoxysilylpropyl) octadecyl dimethyl ammonium chloride (SPODA) were synthesized and coated onto cotton fibers using a pad-dry process (PD) and the traditional pad-dry-cure process (PDC). The coated cotton swatches were characterized by FT-IR and SEM. The quaternary ammonium salt showed a relatively lower inactivating bacteria efficacy than did the N-halamine compounds. The chlorinated swatches coated with both SPH and SPODA using the PD process could inactivate about 7 logs of the Staphylococci aureus within 5–10 min and 7 logs of Escherichia coli O157:H7 within 10–30 min, respectively. The addition of quats in N-halamine coatings improved antimicrobial activity against Gram-negative bacteria E. coli O157:H7. However, this result was not observed when the PDC process was applied in coatings because of the increasing hydrophobicity of the coated samples under high coating temperature.     

Enhanced thermal decomposition,laser ignition and combustion properties of NC/Al/RDX composite fibers fabricated by electrospinning

Cellulose - Nano aluminum (Al) has always been the research hotspot in the field of energetic materials because of its high energy density and combustion temperature, and has been considered to be...     

PVC-laponite nanocomposites: Enhanced resistance to UV radiation

Laponite, a clay mineral, was treated by intercalation of two different phthalocyanine amide polymers based on aliphatic amine (MF-PcAl) as well as an aromatic one (MF-PcAr). The intercalation of the amide polymers was followed by X-ray diffraction (XRD). The different forms of laponite even in its untreated form were incorporated into poly(vinyl chloride) (PVC) formulations via melt blending method to produce PVC-laponite nanocomposites of exfoliated type which was confirmed by XRD. The stabilization mode of the incorporated laponites against UV radiation is discussed based on scanning electron microscopy (SEM), XRD, UV-vis absorption and transmission spectra, electron paramagnetic resonance (EPR), differential scanning calorimetry (DSC) and mechanical properties. Improved resistance to the UV degradative effect was explained on the light of the ability of the clay to scatter the light and to trap any growing radicals as well in addition to the sacrificing role of phthalocyanines by absorbing the incident light on the expense of the PVC and transmitting the rest of the light in another non-harmful form such as heat.     

Kinetic models of natural gas combustion in an internal combustion engine

In this study, combustion of methane was simulated using four kinetic models of methane in CHEMKIN 4.1.1 for 0-D closed internal combustion (IC) engine reactor. Two detailed (GRIMECH3.0 & UBC MECH2.0) and two reduced (One step & Four steps) models were examined for various IC engine designs. The detailed models (GRIMECH3.0, & UBC MECH2.0) and 4-step models successfully predicted the combustion while global model was unable to predict any combustion reaction. This study illustrated that the detailed model sh...     

Synthesis and characterization of cotton candy-PANI: Enhanced supercapacitance properties

Polyaniline (PANI) is a popular material for making supercapacitor electrodes due to its long-term cycle stability, specific capacitance, conductivity, mechanical robustness, scalability, and viability. All of these characteristics may be improved by introducing new architecture and employing alternative synthetic methods. The current study covers the synthesis and electrochemical performance of the protonated emeraldine salt of a newly architected PANI, which is referred in this article as cotton candy polyaniline (cc-PANI). It was found that the direct current (DC) conductivity and specific capacitance of PANI and cc-PANI electrodes are 1.21 × 10^?4 Scm^?1, 3.73 × 10^?4 Scm^?1 and 161.66 Fg^-1, 203.33 Fg^-1 at a current density of 1Ag^-1 in a 1 M H2SO4 electrolyte solution respectively. Further, the static contact angle (CA) was found to be 38.3^o and 32.6^o for PANI and cc-PANI. Here, a novel designed cc-PANI was effectively synthesised and characterised. This strategy offers new hopes in the realm of PANI with improved supercapacitance qualities.     

Speciation of the inorganic components in brown coal

Brown coal samples from different deposits have been analyzed for the bonding forms of their inorganic components. Besides the analysis of the dried coals, ashing techniques (high and low temperature ashing) and extraction procedures with different solvents (acids, bases, complexation agents, organic solvents with different polarity) have also been investigated. ESCA, PIXE, INAA, ICP-Atomic Emission Spectroscopy, NMR and Ionchromatography have been applied to the analysis of coals, ashes, wet ashing and extraction products. The bonding behavior of more than 40 elements could be characterized. Conclusions about geological and geochemical processes during and after coalification could be drawn.     

Thermal decomposition of pharmaceutical preparations containing inorganic components

Summary Differential thermal analysis, thermogravimetry and derivative thermogravimetry have been used for studying the thermal decomposition of 30 formulations, most of which contained salts of metals.

---

Thermische Zersetzung pharmazeutischer, anorganische Bestandteile enthaltender Präparate

Zusammenfassung Differentialthermische Analyse, Thermogravimetrie und Derivat-Thermogravimetrie wurden für die Untersuchung des thermischen Zerfalls von 30 Medikamenten, von denen die meisten Metallsalze enthielten, herangezogen. Die Eignung dieser Methoden zur Identifizierung einzelner Präparate sowie für ihre qualitative und quantitative Analyse wurde gezeigt.

     

Synthesis and thermal behaviour of gallium-substituted aluminosilicate inorganic polymers

A combined sol-gel and solid-state method reported for the synthesis of gallium silicate analogues of aluminosilicate inorganic polymers has also been extended to the formation of related compounds with a range of Al-for Ga substitutions. Homogeneous, robust products were obtained at an optimum composition of SiO(2):(Ga(2)O(3) + Al(2)O(3)) = 7. After curing at 40 °C, all the products were typically X-ray amorphous, and the Al and Ga was shown by (27)Al and (71)Ga MAS NMR spectroscopy to be in solely tetrahedral coordination. The (29)Si MAS NMR spectra were as expected for silicate inorganic polymers, but also indicated the presence of some unreacted silica. Electron microscopy in conjunction with EDS elemental mapping showed that the Ga, Al and Si was homogeneously distributed in the products. Thermal treatment of these compounds results in endothermic water loss at about 75-160 °C followed by an exothermic event at about 950 °C corresponding to crystallization of KGaSi(2)O(6) in the gallium end-member. By contrast, the Al-substituted compounds never fully crystallised, but melted at 1200 °C to an X-ray amorphous product.     

Use of inorganic materials to enhance thermal stability and flammability behavior of a polyimide

While a great variety of high temperature polyimide materials exist, these materials are being subjected to higher and higher use temperatures in oxidative and environmentally aggressive environments. There is a limit to the extent one can take a polyimide before it will oxidize and subsequently suffer property degradation, thermal decomposition, and structural failure. Therefore, we instead sought to use materials which do not oxidize (inorganic materials) to enhance the polyimide composition and perhaps move the properties of the organic polymer more into the realm of ceramics while maintaining polyimide composite weights and processing advantages. In this paper we present results of the combination of inorganic micron sized particles with and without carbon nanofibers to produce a variety of highly inorganic particle filled polyimides. These polyimides were tested for thermal stability and flammability in resin pellet form and as a protective coating for a carbon-fiber composite structure. Our results demonstrate that the resin with inorganic particles exhibited significant reductions in flammability by themselves, but minimal flammability reduction when used as a thin coating to protect a carbon-fiber composite. Further, the gains in thermal stability are limited by the thermal stability of the polyimide matrix, suggesting that more work is needed in measuring the limits of inorganic fillers to improve thermal stability. Still, the results are promising and may yield polyimide systems useful for providing resistance to damage from high heat flux exposures/fire risk scenarios.