Combustion synthesized vanadia rods for environmental applications

Rod‐shaped V₂O₅ was synthesized using the solution combustion technique, and the morphology of the compound was confirmed by TEM. Rods of an average diameter of 500 nm and length 3–6 times the diameter were obtained after the calcination of freshly prepared V₂O₅ at 550°C for 24 h. Pd metal nanoparticles of 20 nm size were deposited onto the rods using the wet impregnation technique. The as‐synthesized, calcined and Pd impregnated V₂O₅ were characterized by a wide variety of techniques including energy dispersive X‐ray spectroscopy and X‐ray photoelectron spectroscopy. These compounds were tested for CO oxidation, adsorption, and photocatalytic degradation of dyes. The 1% Pd/V₂O₅ showed a high activity for CO oxidation, the as‐synthesized compound showed activity for the adsorption of cationic dyes, whereas the calcined V₂O₅ sample showed high rates of photocatalytic degradation of dyes. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Atrazine Removal in Municipal Secondary Effluents by Fenton and Photo‐Fenton Treatments

Alternative water sources, including effluents from municipal wastewater treatment plants (MWTP) are necessary to meet increasing water demand. Advanced oxidation processes based on the Fenton reaction were applied to remove atrazine from the secondary effluents of a MWTP that uses activated sludge. Fenton, UV‐A photo‐Fenton, and UV‐C photo‐Fenton treatments were tested. Atrazine removal percentages were around 20 % for Fenton, 60 % for UV‐A photo‐Fenton and 70 % for UV‐C photo‐Fenton treatments, respectively. Organic matter mineralization by Fenton treatment was monitored and no significant reduction was observed. However, organic matter oxidation in terms of COD reduction of around 30 and 40 % were achieved by Fenton and photo‐Fenton processes, respectively. The photo‐Fenton process with UV‐C is a useful technique for atrazine degradation, leading to higher degradation than with UV‐A while also being more attractive in an economic point of view.     

DSC determination of thermally oxidized olive oil

The feasibility of using DSC as an analytical method to evaluate the autoxidation of olive oil at 50°C and thermal oxidation at 93 and 180°C in 10-mL airtight vials was studied. DSC peak enthalpy and peak crystallization temperatures were compared with headspace oxygen depletion and headspace volatiles in oxidized oil samples. A single crystallization peak was found in olive oil. The crystallization peak shifted to lower temperatures, and the enthalpy associated with this phase transition decreased as the exposure time increased at 93 and 180°C. DSC peak enthalpy in olive oil at 50, 93, and 180°C showed correlations of 0.84, 0.91, and 0.95, respectively, with headspace oxygen depletion in sample bottles. Correlation of DSC initial peak temperature with headspace oxygen depletion was 0.53, 0.87, and 0.95 at 50, 93, and 180°C, respectively. Correlations of DSC peak enthalpy and initial peak temperature with headspace volatiles at 180°C were 0.95 and 0.97, respectively. These results indicate that DSC is a good analytical method to determine the oxidative stability of olive oil at frying temperature.     

Fire performance of charring closed‐cell polymeric insulation materials: Polyisocyanurate and phenolic foam

Results are presented from 2 series of ad hoc experimental programmes using the cone calorimeter to investigate the burning behaviour of charring closed‐cell polymeric insulation materials, specifically polyisocyanurate (PIR) and phenolic (PF) foams. These insulation materials are widely used in the construction industry due to their relatively low thermal conductivity. However, they are combustible in nature; therefore, their fire performance needs to be carefully studied, and characterisation of their thermal degradation and burning behaviour is required in support of performance‐based approaches for fire safety design. The first series of experiments was used to examine the flaming and smouldering of the char from PIR and PF. The peak heat release rate per unit area was within the range of 120 to 170 kW/m² for PIR and 80 to 140 kW/m² for PF. The effective heat of combustion during flaming was within the range of 13 to 16 kJ/g for PIR and around 16 kJ/g for PF, while the CO/CO₂ ratio was within 0.05 to 0.10 for PIR and 0.025 to 0.05 for PF. The second experimental programme served to map the thermal degradation processes of pyrolysis and oxidation in relation to temperature measurements within the solid phase under constant levels of nominal irradiation. Both programmes showed that surface regression due to smouldering was more significant for PF than PIR under the same heat exposure conditions, essentially because of the different degree of overlap in pyrolysis and oxidation reactions. The smouldering of the char was found to self‐extinguish after removal of the external heat source.     

Effects of ferric chloride on thermal degradation of γ‐oryzanol and oxidation of rice bran oil

The kinetics of γ‐oryzanol degradation in antioxidant‐stripped rice bran oil were investigated at 180°C for 50 h. Ferric chloride was added to the oil at different concentrations (0, 2.5, 5.0, and 7.5 mg/kg‐oil) to determine the degradation reaction rate of γ‐oryzanol and the extent of lipid oxidation (peroxide value and p‐anisidine value). It was found that the losses of γ‐oryzanol and its four components (cycloartenyl ferulate, 24‐methylene cycloartanyl ferulate, campesteryl ferulate, and β‐sitosteryl ferulate) could be described by a first‐order kinetics model. The degradation rate constant, k, linearly increased (p < 0.05) with the ferric chloride concentration, and increased about 1.5 times when 7.5 mg/kg‐oil ferric chloride was added. Ferric chloride addition also accelerated the lipid oxidation of rice bran oil significantly (p < 0.05). Practical applications: This paper describes the kinetic analysis of the degradation of γ‐oryzanol, a major phytochemical in rice bran oil, at its frying temperature. The results indicated that iron in the form of ferric chloride accelerated both the degradation of γ‐oryzanol and lipid oxidation.     

Thermo‐oxidative degradation behavior of recycled polypropylene

This study has been carried out to mimic the thermo‐oxidative degradation of polypropylene (co‐PP) during service life and recycling. Injection molded specimens were heat aged at 130°C for different times up to maximum of 300 h to simulate the degradation of co‐PP during the service life. These aged specimens were mixed with stabilizers in internal mixer and again heat aged up to 300 h. A small increase in melt flow rate (MFR) value was observed for aged co‐PP but it showed large increase after recycling. The presence of carbonyl peak at 1713 cm⁻¹ confirmed the oxidation of co‐PP during aging and it increases with aging time. Carbonyl index (CI) is increased in recycled sample with aging, whereas oxidation induction time (OIT) decreased. The stabilizers used during reprocessing are quite effective in controlling the thermo‐oxidative degradation of the polymer during processing and aging. The thermogravimetric analysis shows that the onset of degradation temperature starts at low temperature for recycled sample as compared to virgin co‐PP. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of novel poly(phenylene sulfide) containing a chromophore in the main chain

A kind of novel poly(phenylene sulfide)s (PPSs) containing a chromophore group were synthesized by the reaction of dihalogenated monomer and sodium sulfide (Na₂S.xH₂O) via nucleophilic substitution polymerization under high pressure. The polymers were characterized by Fourier transform infrared spectroscopy, ultraviolet spectroscopy, fluorescence spectroscopy, XRD, DSC, TGA, mechanical testing and dissolvability experiments. The intrinsic viscosity of the polymers obtained with optimum synthesis conditions was 0.22 ? 0.38 dl g^?1 (measured in 1‐chloronaphthalene at 208 °C). These polymers were found to have good thermal performance with a glass transition temperature (T_g) of 90.5 ? 94.6 °C and initial degradation temperature (T_d) of 475–489 °C, showing improved thermal properties compared with homo‐PPS. At the same time the resultant resins had a high tensile strength of 67.5 ? 74.1 MPa and compressive strength of 70.7 ? 85.4 MPa. Additionally, these polymers exhibited a weak UV ? visible reflectivity minimum at 450–570 nm, and the fluorescence spectra of the polymers showed maximum emission around nearly 370 nm. Also they showed excellent chemical resistance and another special property ? bright shiny colors changed into different colors in acid solution. © 2014 Society of Chemical Industry     

苯胺和环氧丙烷共聚物的制备及其性能

采用循环伏安法制备了苯胺和环氧丙烷导电高分子共聚物（PAN-PPO）,采用扫描电子显微镜（SEM）和差热分析等对聚合物进行表征,同时研究其对甲醇的电催化氧化作用.结果表明：在相同的条件下,PAN-PPO的聚合氧化还原峰电流和电导率均高于聚苯胺（PAN）;PAN-PPO具有均匀致密的纳米纤维网状结构,纤维直径小于70 nm;PAN-PPO的热分解温度略低于聚苯胺（PAN）;在甲醇酸性体系中,PAN-PPO对甲醇具有较好的电催化活性,此反应受扩散控制.     

The Nanocrystalline Nickel with Catalytic Properties on Methanol Oxidation in Alkaline Medium

The hexagonal closed packed (hcp) nanocrystalline nickel (Ni), with an average diameter of 9.7 ± 2.27 nm was deposited uniformly on composite graphite (CG) by the rapid scanning (6,500 mVs^–1) voltammetry technique. The hcp‐nano Ni‐modified CG electrode was investigated for the catalytic oxidation of methanol in alkaline medium through the formation of NiOOH. A high anodic current was obtained at peak potential of +570 mV vs Ag/AgCl. Both the scan rate and the methanol concentration affected the oxidation of methanol. The results showed that catalytic activity had increased with decrease in Ni particle diameter. It was also shown that the hcp‐nano Ni/CG modified electrode was the most efficient catalyst in the oxidation of methanol.     

Phase Development and Shrinkage of Reaction-Bonded Mullite Composites with Silicon Carbide of Different Particle Sizes

Mullitization temperatures and mechanical properties of reaction-bonded mullite composites were investigated using silicon carbide (SiC) of two different particle sizes (180 nm and 2.5 μm) as one of the starting components. The smaller SiC particle size resulted in earlier mullitization, lower final densities, and lower strength of these composites. The sintering shrinkage of these composites was investigated. Low-to-zero shrinkage was rendered possible via volume expansions that were associated with the oxidation of SiC and aluminum in the green material. Green bodies that contained 55 vol% aluminum were compacted to 70% of the theoretical density. The materials showed a linear sintering shrinkage of <1% and had a four-point bend strength of 430 MPa. Samples that were made from precursors with the coarse (2.5 μm) SiC were covered by a porous outer layer after firing in air. This layer led to anisotropy in shrinkage. The porosity of this outer layer was attributed to the oxidation of residual SiC during sintering and the trapping of gaseous oxidation products. Samples that were made from the fine (180 nm) SiC did not exhibit such a layer and showed isotropic shrinkage.     

Structure and processability of iodinated poly(vinyl alcohol) (III)‐structure of films iodinated in solution before casting

Films iodinated at solution before casting (IBC films) were prepared by casting aqueous solutions of 10 wt % poly(vinyl alcohol) (PVA) containing selected quantities of I₂/KI. The quantity of I₂/KI was controlled to obtain 15.2, 39.8, 83.2, 117.0, and 140.1%. The Thermogravimetry (TG) curves of the IBC film exhibited three distinct zones corresponding to the evaporation of H₂O and I₂ molecules (zone I), evaporation of I₂ and partial decomposition of side groups (? OH) (zone II), degradation of the remaining side groups and partial degradation of the main chain (zone III‐1), and degradation of the remaining main chain and the char zone corresponding to KI. The crystalline structure of the film with a weight gain of 15.2% was almost the same as that of the pure PVA, and the film with the weight gain of 140% was almost amorphous. The differential scanning calorimetry (DSC) thermograms of the IBC films with a weight gain of 15.2% and 39.8% indicated endothermic single or double peaks at around 180°C, corresponding to the crystal melting and degradation of side groups; those with weight gains of 83.2% and above indicated exothermic peaks at around 170°C, corresponding to crystallization, and broad endothermic peak at around 180–200°C, corresponding to the crystal melting and degradation of side groups. The dynamic mechanical α_a transition of the IBC film with the weight gain of 140.1% appeared at around 20°C. X‐ray diffraction and DSC analysis of deiodinated films show that the crystal structure, on deiodination of all the IBC films, regardless of crystallinity, returned to that of the pure PVA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3497–3502, 2006     

Modification of LLDPE using esterified styrene maleic anhydride copolymer: Study of its properties and environmental degradability

Linear low‐density polyethylene (LLDPE) was blended with decanol‐esterified styrene maleic anhydride copolymer (MDESMA) with an aim to enhance the environmental degradability of polyethylenes. Styrene‐maleic anhydride copolymer (SMA) was synthesized by precipitation polymerization, using benzoyl peroxide (BPO) as initiator. SMA was esterified with a long‐chain monoalcohol, n‐decanol, using methyl ethyl ketone (MEK) as solvent at 80°C to obtain monoesterified styrene‐maleic anhydride (MDESMA). Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA) were performed to characterize SMA and MDESMA. IR spectra of MDESMA showed a decrease in intensity of peak responsible for carbonyl absorption of a five‐membered ring anhydride group along with broadening of carboxyl O? H stretching peak. TGA showed two‐stage degradation for SMA and MDESMA. LLDPE was blended with MDESMA in single‐screw extruder and blends were characterized thermally by DSC and TGA. A single endothermic melting peak of LLDPE/MDESMA blend was observed. Films of the blends, formed by compression molding, showed an increase in modulus of elasticity but a decrease in elongation at break with increasing concentration of MDESMA. LLDPE/MDESMA blend compositions when kept in phosphate/citric acid buffer solution (pH ～ 8) showed initial weight gain because of water absorption and subsequently loss in weight due to dissolution of soluble component of blends. Film samples of blends kept for soil burial also showed similar behavior. Contact‐angle measurement of film samples of the blends showed an increase in value on soil burial, indicating degradation/dissolution of MDESMA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 102–108, 2004     

Effect of copper on the curing and structure of a DICY‐containing epoxy composite system

The curing and structure of an epoxy system containing dicyandiamide (DICY) as hardener were studied as a function of temperature and the presence or absence of copper with the use of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy in photoacoustic mode (FTIR‐PAS). Spectroscopic analysis of specimens taken from the DSC helped to clarify the reaction mechanism in terms of the different schemes that have been proposed. The initial stages, corresponding to the first peak in the DSC exotherm, involve the usual epoxide‐amine reactions closely followed by a reaction between DICY nitrile groups and hydroxyl groups to form structures containing iminoether and urea groups. These reactions are slightly retarded in the presence of copper. At higher temperatures, corresponding to the second peak in the exotherm, these structures are transformed into others believed to contain urethane ester groups. This reaction, which may be considered to constitute a form of degradation, is significantly accelerated in the presence of copper. The effect is particularly large around 180°C, a temperature commonly used to cure such systems, so the results have important practical implications, for example, in the lamination of circuit boards. © 2000 Government of Canada. Exclusive worldwide publication rights in the article have been transferred to John Wiley & Sons, Inc. J Appl Polym Sci 75: 1458–1473, 2000     

An optimization study on microwave irradiated decomposition of phenol in the presence of H2O2

BACKGROUND Removal of phenol from industrial waste waters involves basic techniques namely extraction, biodegradation, photocatalytic degradation, etc. Among the available processes, the oxidation of phenols using H₂O₂ is a suitable alternative because of low cost and high oxidizing power. The application of an oxidation process for the decomposition of stable organic compounds in waste water leads to the total degradation of the compounds rather than transferring from one form to another. Since oxidation using Fenton's reagent is more dependent on pH, in this present work it was proposed to use H₂O₂ coupled with microwave irradiation. The effects of initial phenol concentration, microwave power and the irradiation time on the amount of decomposition were studied. RESULTS: In the present work experiments were conducted to estimate the percentage degradation of phenol for different initial concentrations of phenol (100, 200, 300, 400 and 500 mg L^?1), microwave power input (180, 360, 540, 720 and 900 W) for different irradiation times. The kinetics of the degradation process were examined through experimental data and the decomposition rate follows first‐order kinetics. Response surface methodology (RSM) was employed to optimize the design parameters for the present process. The interaction effect between the variables and the effect of interaction on to the responses (percentage decomposition of phenol) of the process was analysed and discussed in detail. The optimum values for the design parameters of the process were evaluated (initial phenol concentration 300 mg L^?1, microwave power output 668 W, and microwave irradiation time 60 s, giving phenol degradation 82.39%) through RSM by differential approximation, and were confirmed by experiment. CONCLUSION: The decomposition of phenol was carried out using H₂O₂ coupled with microwave irradiation for different initial phenol concentrations, microwave power input and irradiation times. The phenol degradation process follows first‐order kinetics. Optimization of the process was carried out through RSM by forming a design matrix using CCD. The optimized conditions were validated using experiments. The information is of value for the scale up of the oxidation process for the removal of phenol from wastewater. Copyright © 2008 Society of Chemical Industry     

Formation and decomposition of stigmasterol hydroperoxides and secondary oxidation products during thermo‐oxidation

The oxidation mechanisms of stigmasterol at 100 and 180 °C were investigated by using the HPLC‐UV‐FL method. An overall picture of the oxidation status was achieved with a single HPLC analysis, enabling us to monitor the formation and decomposition of both primary and secondary oxidation products. The oxidation behavior of stigmasterol was different at the two temperatures. At 180 °C, the amounts of hydroperoxides increased sharply during the first 10 min and then began to decrease. At 100 °C, the amounts of hydroperoxides increased over the entire experimental period. At 180 °C, all major secondary oxidation products, except 7‐ketostigmasterol, reached a plateau after 40 min of oxidation, while at 100 °C their amounts increased constantly. The same oxidation products were formed at both temperatures, but their distribution differed. At 180 °C, the formation of free radicals at position 7 was more favorable than formation of radicals at position 25. The situation was the opposite at 100 °C; radicals formed more easily at the tertiary position 25. At 180 °C, 7‐ketostigmasterol was dominant after 40 min of oxidation, whereas at 100 °C it was the main oxidation product over the entire experiment.     

Changes in Pore Size Distribution upon Thermal Cycling of TATB‐based Explosives Measured by Ultra‐Small Angle X‐Ray Scattering

Hot‐spot models of initiation and detonation show that voids or porosity ranging from nanometer to micrometer in size within highly insensitive energetic materials affect initiability and detonation properties. Thus, the knowledge of the void size distribution, and how it changes with the volume expansion seen with temperature cycling, are important to understanding the properties of the insensitive explosive 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB). In this paper, void size distributions in the 2 nm to 2 μm regime, obtained from small‐angle X‐ray scattering measurements, are presented for LX‐17‐1, PBX‐9502, and ultra‐fine TATB formulations, both as processed and after thermal cycling. Two peaks were observed in the void size distribution: a narrow peak between 7–10 nm and a broad peak between 20 nm and about 1 mm. The first peak was attributed to porosity intrinsic to the TATB crystallites. The larger pores were believed to be intercrystalline, a result of incomplete consolidation during processing and pressing. After thermal cycling, these specimens showed an increase in both the number and size of these larger pores. These results illuminate the nature of the void distributions in these TATB‐based explosives from 2 nm to 2 μm and provide empirical experimental input for computational models of initiation and detonation.     

Thermal Stability of Gamma Irradiated Low Density Polyethylene Films Containing Hindered Amine Stabilizers

Summary: The thermal stability of gamma irradiated low density polyethylene (LDPE) films in presence of various structures of hindered amine stabilizers (HAS) was investigated by the oxygen uptake method under constant temperature of 180 °C and normal pressure conditions. The thermo‐oxidation was run using air environment. The sigmoidal dependency of oxygen uptake allows the calculation of the main kinetic parameters: oxidation induction time and oxidation rate on the propagation step. The various steps involved in the thermal degradation process were detected by the derivative procedure applied to the dependencies of oxygen uptake on time. It was found that the kinetic parameters of the thermal degradation process, determined by oxygen uptake, revealed the antioxidant role of HAS in γ‐irradiated LDPE films by providing better stability, when compared with the unstabilized samples. Moreover, the results indicated that the dependencies of oxygen uptake on thermal degradation time involved two degradation stages: the former occurring in the ungrafted moiety and the latter taking place after the antioxidant depletion is achieved. The stabilization efficiency of these oxidation inhibitors provides satisfactory thermal resistance to LDPE films, especially those based on an alkoxyamine structure.

Dependencies of oxygen uptake on time at the thermal degradation of LDPE irradiated at 812 kGy. (‐□‐) free of additive; (‐○‐) Tinuvin 123; (‐?‐) Sanduvor PR 31; (‐?‐) Uvasil 299.     

Thermal Oxidation Kinetics of Refined Hazelnut Oil

In this study, oxidation kinetics of refined hazelnut oil heated at the temperature range from 80 to 180 °C was evaluated. The changes in peroxide value, p‐anisidine value, polymer triglyceride content, α‐tocopherol content, and color values during oxidation were best fitted to zero‐order kinetic model. The rate constants for the p‐anisidine value, polymer triglyceride content, and degradation of α‐tocopherol of hazelnut oil increased at the temperatures between 80 and 160 °C, while the rate constant for peroxide value decreased at the temperatures between 80 and 140 °C. The activation energies for the formation of peroxides (at 80–140 °C), secondary oxidation products such as alkenals, the polymer triglycerides, and degradation of α‐tocopherol were found as 47.49, 29.95, 52.65, and 14.22 kJ mol^?1, respectively. The induction period of hazelnut oil was observed to reduce with increasing oxidation times. The increase in the b* value with the oxidation time and temperature was attributed to the fact that the heating process intensified the yellow color of the oil.     

Characterization of polyaniline via pyrolysis mass spectrometry

In this work, direct insertion probe pyrolysis mass spectrometry technique was applied to investigate the thermal and the structural characteristics of electrochemically prepared HCl and HNO₃‐doped polyaniline (PANI) films. It has been determined that the thermal degradation of both samples showed three main thermal degradation stages. The first stage around 50–60°C was associated with evolution of solvent and low‐molecular‐weight species adsorbed on the polymer, the second stage just above 150°C was attributed to evolution of dopant‐based products, and the final degradation stage at moderate and elevated temperatures was associated with evolution of degradation products of the polymer. Chlorination and nitrolysis of aniline during the electrochemical polymerization were detected. Extent of substitution increased as the electrolysis period was increased. Furthermore, for the HNO₃‐doped PANI, the evolution of CO₂ at elevated temperatures confirmed oxidation of the polymer film during electrolysis. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermooxidative degradation behavior of poly(silphenylene–siloxane)s

Copolymers of poly(silphenylene–siloxane) with dimethylsiloxane and diphenylsiloxane with various end groups were synthesized through an Si? H/Si? OR polycondensation process. The thermooxidative degradation behaviors of the copolymers were investigated by thermogravimetric analysis and IR spectrometry techniques. All of the polymers were characterized by a two‐step mass loss. The first one, which peaked at 510–545°C in differential thermogravimetric curves, was mostly caused by the main‐chain depolymerization, whereas the second one, which reached its maximum around 650°C, was caused by side‐group oxidation and Si? C bond scission. The main‐chain depolymerization occurred over a temperature range of some 470–580°C, whereas Si? C bond scission and side‐group oxidation occurred over a temperature range of about 585°C to above 720°C. The incorporation of phenyl groups in the end groups greatly retarded the temperature for the degradation onset of the main chain to 120°C higher. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010