Thermal Degradation Profile Research Articles

Periconium sp. (endophytic fungi) extract mediated sol-gel synthesis of ZnO nanoparticles for antimicrobial and antioxidant applications

The Periconium sp. extract mediated sol-gel process was effectively utilized for the synthesis of ZnO nanoparticles. The aqueous fungal extract acted as chelating agent for the Zn2+ ions and lead to the formation of gel. The dried gel was characterized by X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), Thermogravimetric/differential thermal analysis (TG/DTA) respectively to identify their phase, structural coordination, morphological feature and thermal degradation profile. The XRD analysis reveals that the biosynthesized ZnO nanoparticles are exist in hexagonal wurtzite structure with the average crystallite size of 40 nm. Transmission electron microscopic (TEM) images of the synthesized ZnO nanoparticles did show the quasi spherical shape with 16–78 nm in size. The Dynamic Light Scattering (DLS) analysis showed their zeta potential and hydrodynamic particle size respectively as −88.6 mV and 338 nm. The UV–Visible spectroscopic analysis depicts their band gap energy as 3.15 eV. The synthesized ZnO nanoparticles exhibited excellent antimicrobial activity against Staphylococcus aureus (Gram positive), Escherichia coli (Gram negative) and Candida albicans (fungi) with an average inhibition zone of 16, 14 and 24 mm, minimum inhibitory concentration (MIC) value of 50, 50, 40 μg/ml, the minimum bactericidal/fungicidal concentration (MBC/MFC) of 50 μg/ml and the half maximal inhibitory concentration (IC50) of 22, 38 and 21 μg/ml respectively. Further, the ZnO nanoparticles also exhibited good antioxidant property with the 85.52% free radical quenching for 100 μg/ml concentration.

Effect of particle size and heating rate on pyrolysis kinetics of Nerium oleander

Nerium oleander is a lignocellulosic biomass which is not consumed by cattle due to its poisonous nature. The effect of two important parameters namely particle size and heating rate on thermal degradation profiles of leaves and stems of N. oleander under pyrolytic conditions were studied using thermogravimetric analysis (TGA). Experiments were conducted using heating rates from 5 to 20 °C min−1 in the pyrolysis temperature range of 0–1200 °C under 100 sccm nitrogen flow. Three different particle sizes 125, 500, and 1000 µ were considered for this study. Three degradation stages (each for hemicellulose, cellulose, and lignin) excluding the moisture loss were found for the chosen biomasses irrespective of particle size and heating rate. The kinetic rate parameters for hemicellulose, cellulose, and lignin were found using mass loss data obtained from TGA assuming first order kinetics using Coats–Redfern model. The assumed first order kinetics was proved correct for all the biomasses chosen based on the R2 value for the experimental data. Lower range of activation energy for hemicellulose and cellulose was observed for all particle sizes at lower heating rate when compared with lignin for both leaves and stems of N. oleander.

Catalyzed pyrolysis of SRC poplar biomass. Alkaline carbonates and zeolites catalysts

Poplar biomass of nine different genotypes, from short rotation coppice, was pyrolyzed in a fixed bed reactor using several solid catalysts. Pine bark was used as reference for uncatalyzed pyrolysis. Pyrolysis tests were performed for temperatures in the range 425–500 °C, selected from the thermal degradation profiles obtained by thermogravimetry under N2 flow. All the analyzed poplar genotypes showed similar pyrolysis behavior, with the highest bio-oil yield (53% average value) being obtained for the highest tested temperature (500 °C). In analogous conditions, the pine bark resulted in higher bio-char yields than poplar biomass, due to its larger lignin content.Catalyzed pyrolysis carried out at 500 °C using 10% of catalyst (Wcat/Wbiomass) for H-ZSM5 and FCC (spent catalyst from Fluid Catalytic Cracking unit) zeolites, and Mg and Na carbonates, showed improved gasification with slightly lower liquid production. The FCC catalyst promoted the lowest depreciation of bio-oil yield with the highest decrease of acid functional groups. All the used catalysts were effective to lessen the acidic components of the produced bio-oils thus having a beneficial effect on the pyrolysis liquid products.

Hydrothermal and organic-chemical treatments of eucalyptus biomass for industrial purposes

This study aimed to evaluate the promising feasibility of the hydrothermal pre-processing of eucalyptus wood and eucalyptus bark under organosolv and organic acid conditions to produce a highly concentrated cellulose feedstock. For that, particulate samples of both biomasses were heated in water solutions containing from 0 to 50%vol/vol of ethanol and from 0 to 50 mmol.L−1 of oxalic acid at temperatures between 140 and 180 °C. Significant differences on the thermal degradation profiles were observed for both biomasses indicating the partial hydrolysis converted them into a more homogeneous solid fraction with higher contents of cellulose. It was also observed a significant variation of the glycan content from approximately 39 to 76% for wood particles, whereas the variation for bark was from 32 to 50%. In general, the proposed pre-processing route was considered potentially feasible to concentrate the cellulose/glycan contents of eucalyptus biomasses for subsequent industrial utilization.

Modification of the resistance of two epoxy resins to accelerated weathering using calcium sulfate as a photostabilizer

Epoxy-timber composites have received increasing attention during the last decades because there are many advantages related to their uses as construction materials in applications such as timber bridges. However, the durability of epoxy-timber composites under outdoor conditions has become a concern for many epoxy resins. This study evaluated the chemical, thermal, and mechanical properties of two cured epoxies, the product of the diglycidyl ether of bisphenol A with 2,4-trimethyl-1,6-hexanediamine (DGEBA-TMDA) and the analogous resin prepared with the hydrogenated diglycidyl ether of bisphenol A (HDGEBA-TMDA), each mixed with 2 wt. % calcium sulfate (CS). We hypothesized that the use of CS, as an inorganic UV absorber, could decrease undesirable effects arising from exposure to UV light, moisture, and extreme temperatures.An accelerated aging chamber simulated natural weathering for 1, 2, 3, 4, and 6 months. Chemical changes in cured epoxy systems over time in the presence and absence of CS fillers were determined using Fourier transform infrared spectroscopy (FT-IR). Thermal degradation profiles before and after exposure to accelerated weathering were followed by thermogravimetric analysis (TGA). The glass transition temperatures (Tg) before and after accelerated weathering were measured, and the effect of accelerated weathering on the surface morphology of the epoxy systems was investigated by scanning electron microscopy (SEM). In the presence of CS, after 6 months accelerated weathering the tensile strength of DGEBA-TMDA reduced by 23.8 ± 2.4%, compared to 46.5 ± 5.5% in its absence, while the corresponding values for HDGEBA-TMDA were 21.4 ± 2.1% and 28.7 ± 1.8%.

Characterization of Cassava Fiber of Different Genotypes as a Potential Reinforcement Biomaterial for Possible Tissue Engineering Composite Scaffold Application

Cassava bagasse contains considerable amount of natural single elementary cellulose fibers and white thick root fiber (thick-core fiber) that has seen frequent application in the packaging industry as reinforcement for plastic composite development. However, a review of the literature was unable to find any study that characterized the material properties (such as tensile properties) of both the single elementary and white thick-core cassava cellulose fibers), and their application as potential reinforced filler in tissue engineering scaffold development. In this study, the tensile properties, morphology, crystallinity and thermal degradation profile of non-chemically treated single elementary cellulose fibers and thick-core fibers of different cassava genotypes were investigated. Fibers were tested according to ASTM C1557 under direct tension in a standard mechanical testing system and the cross-sectional area of the fractured regions of the fibers were determined using a 3D optical microscopy method. Cassava fibers of different genotypes did not show any significant difference in tensile properties, with average tensile strength ranging from (5.1–7.3 MPa), Young’s modulus (258–333 MPa) and failure strain (3.4–4.2 %). Tensile test conducted for several gage lengths did not influence the tensile strength and Young’s modulus of the fibers, however, strain-at-break depended on gage length. Single elementary and thick-core fibers showed similar surface morphology, degree of crystallinity (ranging from 21–40 %) and tensile properties with some variation in elastic modulus. Cassava fibers are thermally stable around 100–200 oC, where processing could be performed. Preliminary results showed an improvement in the mechanical properties of a gelatin scaffold when cassava cellulose microfibers were used as reinforcing fillers. The current findings show that cassava fiber has a reasonable mechanical strength, stiffness and thermal stability, and could be considered as a reinforced biomaterial to improve the mechanical integrity of tissue engineering scaffolds.

Enhancing the Phenolic Content of Bio-Oil by Acid Pre-Treatment of Biomass

Pyrolysis of lignocellulosic biomass with acidic pre-treatment to produce valuable bio-chemicals has been carried out in an integrated pyrolysis-gas chromatograph/mass spectrometry system. Three different waste biomasses (fir wood sawdust, pine wood sawdust and nutshell) were subjected to acidic solution to specify the acid pre-treatment effect on biomass chemical structure, thermal degradation profile and pyrolysis products. Post acid pre-treatments, the changes in the biomasses and thermal degradation profile were studied through proximate, structure and ultimate analysis and thermogravimetric. The pre-treatment significantly reduced the inorganic, cellulose and hemicellulose content in biomass samples. According to the pyrolysis experiment results, acid pre-treatment provided the increasing of the amount of phenolic in the degradation products at 10 min pyrolysis time. All the results would assist further understanding of thermal decomposition and thermo-chemical application for bio-fuels and bio-chemicals of fir wood sawdust, pine wood sawdust and nutshell.Article History: Received January 15th 2018; Received in revised form May 24th 2018; Accepted 7th June 2018; Available onlineHow to Cite This Article: Ozbay, N. and Yaman, E (2018) Enhancing the Phenolic Content of Bio-Oil by Acid Pre-Treatment of Biomass. Int. Journal of Renewable Energy Development, 7(2), 163-169.https://doi.org/10.14710/ijred.7.2.163-169

Production and characterisation of biodegradable PLA nanoparticles loaded with thymol to improve its antimicrobial effect

Thymol is widely recognised as an antibacterial compound. However, its use in food technology is hindered by its high volatility, its light sensitivity and its low solubility in water. To overcome these drawbacks, the preparation of nanoparticles using polylactic acid (PLA) is proposed in this study.The average size of the nanoparticles and thymol encapsulation efficiency parameters were studied using different PLA and thymol concentrations. Furthermore, the morphology, the storage stability of the nanoparticles at several pHs and the in vitro thymol release profile were also studied, as well as their thermal degradation profile. Finally, their antimicrobial activity on a real food model was measured, using for this purpose apple pieces previously inoculated with E. coli.The PLA was found to be the key variable in optimizing the nanoparticle preparation, producing spherical nanoparticles with a thymol encapsulation efficiency of 60.3 ± 8%. These nanoparticles showed a high storage stability at several pHs and improved antimicrobial properties in comparison with the non-encapsulated thymol.

Tasar silk fiber waste sericin: New source for anti-elastase, anti-tyrosinase and anti-oxidant compounds

The present study investigates the properties of sericin extracted from tasar silk fiber waste (TSFW). The surface morphology of TSFW was observed by scanning electron microscope (SEM). SEM images revealed the removal of residual sericin over the surface of TSFW. The molecular weight distribution of sericin was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The results suggested that TSFW sericin represented a family of proteins with wide-ranging molecular weight distribution (11–245 kDa). Structural determination by FTIR revealed the presence of both α-helical and β-sheet structures. The colour was studied by colorimeter indicating less brightness, more red and yellow colour intensities. The carbon: nitrogen ratio (C:N) was studied by CHNS element analyzer and the ratio is 5.15-7.85. Thermal properties of TSFW sericin have been studied by thermogravimetric analysis (TGA) method. TGA curve showed higher thermal stability and variable degradation profiles. Furthermore, TSFW sericin contains 17 amino acids where serine, aspartic acid and glycine are the more significant compounds (54.34–60.49%). In addition, sericin was found to inhibit tyrosinase, elastase and glutathione-S-transferase activity, and had apparent radical scavenging impacts on 2.2‑diphenyl‑1‑picryl‑hydrazil (DPPH), hydrogen peroxide and inhibition of lipid peroxidation. Result suggested that TSFW sericins might be a valuable ingredient for cosmoceutical products.

Synthesis and mesophase characterization of methacrylate based three phenyl ring core side chain liquid crystalline copolymers

A new series of side chain liquid crystalline copolymers consisting of a mesogenic monomer and a non-mesogenic n-butyl methacrylate are prepared by free radical solution polymerization. The mesogenic monomer is synthesized by a multistep route and is built with side arm core consisting of three phenyl rings linked by an ester and a terminal alkoxy chain at one end and hexamethylene spacer between methacyrlate unit and the phenyl ring core. The copolymers are synthesized with different feed ratios of liquid crystalline monomer and n-butyl methacrylate to realize composition dependent copolymers. The mesogenic monomers are characterized by FT-IR, 1H and 13C NMR while for a representative mesogen solution two-dimensional (2D) NMR experiments are also carried out. The hot-stage optical polarized microscopy, differential scanning calorimetry and variable temperature powder X-ray diffraction investigations revealed the existence of enantiotropic nematic (N) and smectic C (SC) mesophases for the copolymers. The weight average and number average molecular weight of the copolymers are found to be in the range 1.6×104 to 3.7×104g/mol from gel permeation chromatography. Thermal degradation profile of mesogenic copolymers investigated by thermogravimetric analysis revealed that the copolymers are stable till 335°C in nitrogen atmosphere. The copolymer compositions were determined using 1H NMR analysis.

Thermogravimetric analyses and kinetic modeling of three Cameroonian biomass

Pyrolysis and combustion processes of three Cameroonian biomass have been performed in a thermobalance to determine their thermal degradation profiles and the associated kinetic parameters. The samples were heated from ambient temperature to $$900\,{{}^\circ }{\hbox {C}}$$ under four low temperature rates (5, 10, 15 and $$20\, {{}^\circ }{\hbox {C}}\,\hbox {min}^{-1}$$ ) and under non-oxidative (nitrogen) or oxidative (synthetic air) atmospheres. The kinetic parameters associated with the pyrolysis of the different samples have been estimated either using a differential isoconversional method with two reaction functions or through the extended independent parallel reaction (EIPR) model and these sets of values are compared. Under nitrogen, the mean values of the activation energies obtained using a differential isoconversional method with Mampel’s reaction function are found equal to $$121.2\,{\hbox {kJ}}\,\hbox {mol}^{-1}$$ for oil palm kernel samples, to $$158.8\,{\hbox {kJ}}\,\hbox {mol}^{-1}$$ for movingui samples and to $$172.5\,{\hbox {kJ}}\,\hbox {mol}^{-1}$$ for padouk samples. When using the 3D diffusion function, the mean value of the activation energies is the same for the two first samples and increases to $$178.8\,{\hbox {kJ}}\,\hbox {mol}^{-1}$$ for padouk samples. When applying the EIPR model, the activation energies of the cellulose part (the main part of these lignocellulosic biomass) of the samples are, respectively, equal to 142.5, 155.2 and $$149.0\,{\hbox {kJ}}\,\hbox {mol}^{-1}$$ and do not highly vary with the applied temperature ramp. Under air, the values of the kinetic parameters have been determined using the EIPR model and the values of the activation energies slightly vary with the temperature ramp for the three samples.

Synthesis and characterization of poly (ionic liquid) derivatives of N-alkyl quaternized poly(4-vinylpyridine)

The main motivation of this work is to obtain poly (ionic liquids) (PILs) derived from poly (4-vinyl pyridine) of different hydrophobic character containing BF4−, PF6−, (CF3SO2)2 N− and CF3SO3− as counterions. PILs were synthesized from N-alkyl quaternized poly(4-vinylpyridine) P-4VP+-CnBr− with different alkyl chain length, n=2, 4, 5 and different molecular weights (60.000 and 160.000g/mol). The systems obtained were compared with the polyelectrolyte of origin, i.e., the N-alkyl quaternized poly(4-vinylpyridine). The molecular characterization of PILs was obtained by FT-IR, 1H NMR and 19F NMR. Moreover, the thermal analysis of these systems was by carried out by differential scanning calorimetry (DSC) and thermogravimetry (TGA) techniques. Thermal degradation profiles obtained from TGA measurements, varied according to the alkyl chain length, which in turn influenced the obtained values of glass transition temperature (Tg), due to greater or lesser segmental movement of the alkyl chain. The results obtained for the PILs studied were analysed according to alkyl chain length, molecular weight and counter-anion effects. Additionally, P-4VP+-C4 BF4− was used in a preliminary study of chromium (VI) removal from aqueous solution, showing a 72.2% removal of Cr (VI).

Thermally induced chemical evolution in polyimide films investigated by X‐ray photoelectron spectroscopy

Thermally modified polyimide films based on 1,4‐Phenylene diamine (p‐PDA) and 3,3′,4,4′ – Benzophenone tetracarboxylic dianhydride (BTDA) were prepared and their chemical structure transformation after thermal treatment at 350 °C–500 °C was investigated. X‐ray diffraction results revealed an increase in the polymer chain order for all treated PI samples as a consequence of the thermal treatment and chain interaction. TGA analysis showed that the heat treatment promoted different thermal degradation profiles. Electron spin resonance evidenced a large population of free radicals as a result of homogeneous bond cleavage when the thermal treatment was performed at 500 °C. X‐ray photoelectron spectroscopy analysis indicated that the chemical structure transformation not only occurs on the outer surface but also in the sub‐surface layer. These results show that controlled fast thermal treatment can produce materials with specific characteristics and may serve as a general strategy for changing both structural and chemical properties of the polymers. POLYM. ENG. SCI., 58:943–951, 2018. © 2017 Society of Plastics Engineers

Thermal degradation of urea‐formaldehyde cellulose composites filled with aluminum particles: Kinetic approach to mechanisms

ABSTRACTThis article reports a study on structural characterization and thermal degradation kinetics of insulating/conducting urea‐formaldehyde cellulose (UFC) composites filled with aluminum particles. Structural characterization of UFC/Al composites carried out by SEM, XRD, and FTIR analyses reveals that composites are fairly homogenous, and the interactions between UFC and aluminum in UFC/Al composites are more probably physical in nature. Measurements of inherent thermal stabilities, probing reaction complexity, and thermal degradation kinetics of UFC and UFC/Al composites have been undertaken by thermogravimetric (TG)/differential thermogravimetric (DTG) analyses under nonisothermal conditions. The integral procedure decompositions temperature (IPDT) elucidates significant thermal stability of UFC, and higher aluminum contents in composites are capable of enhancing the thermal stability of UFC resin. TG/DTG analyses suggest highly complicated thermal degradation profiles of UFC and UFC/Al composites, which consist of various parallel/consecutive reactions. Generalized linear integral isoconversional method has been employed to determine the activation energies of thermal degradation processes. Substantial variations in activation energies of UFC and UFC/Al composites with the advancement of reaction verify their multi‐step reaction pathways. Advanced reaction model determination methodology with the help of a novel kinetic function F(α,T) reveals that the multi‐step thermal degradation of UFC goes to completion by principally following intricate nucleation/growth mechanisms. It is also found that aluminum more likely participates in the thermal degradation of resin and tends to alter its reaction mechanism. Detailed interpretations of the obtained kinetic parameters are given, and their probable physical significances are discussed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44826.

Synthesis and characterization of biobased poly(butylene succinate-ran-butylene adipate). Analysis of the composition-dependent physicochemical properties

Fully biobased aliphatic random poly(butylene succinate-ran-butylene adipate) (PBSA) copolyesters and the corresponding homopolyesters (poly(butylene succinate) (PBS) and poly(butylene adipate) (PBA)) with high molar mass, were synthesized with different succinic acid/adipic acid (SA/AA) molar ratio by transesterification in melt, using titanium (IV) isopropoxide as an effective catalyst. All synthesized copolyesters were fully characterized by various chemical and physicochemical techniques including NMR, SEC, FTIR, WAXS, DSC and TGA. The final copolyesters molar compositions were identical to the feed ones. The different sequences based on succinate and adipate were randomly distributed along the chains. All the corresponding copolyesters showed an excellent thermal stability with a degradation onset temperature higher than 290°C and a thermal degradation profile driven by the major diacid component. Glass transition temperatures of copolyesters decreased with the adipate content due to the decrease of the chain mobility, following the Gordon-Taylor relation. PBSA showed a pseudo-eutectic melting behavior characteristic of an isodimorphic character. Besides, the presence of both crystalline phases was observed for adipate content in the range 50–60mol.%.

Comparative study of printed circuit board recycling by cracking of internal layers using organic solvents-dimethylformamide and dimethylacetamide

Dissolution studies of the substrate resin of waste printed circuit boards (WPCBs) in two organic solvents have shown that dimethylacetamide (DMAc) is more effective than dimethylformamide (DMF). Variation of dissolution parameters elucidated that DMAc results in 20% more resin dissolution when the temperature is increasing from 120 °C to 140 °C. It also results in 217% higher dissolution efficiency when the WPCBs:DMAc (w/v) ratio is increased to 3:10 from 1:10. The DMAc showed higher dissolution of the resin than DMF, for WPCBs of different size under conditions viz.- 140 °C, and 3:10 (w/v) WPCB:solvent ratio. The WPCBs of 2.25 cm2 size were completely separated into glass fiber matrix and copper foils in 180 min. Dissolution of resin is associated with the hydrogen bonding interaction with parent DMAc molecule. Spent DMAc has been regenerated by rotary decompression evaporator and it’s chemical structure and boiling point were found similar to pure DMAc. Dissolved solute in the DMAc has been recovered as the residue during regeneration. The residue and exhibits a thermal degradation profile and chemical structure similar to untreated brominated epoxy resin.

Poly(phosphorodiamidate)s by Olefin Metathesis Polymerization with Precise Degradation.

Degradable polymers are a currently growing field of research for biomedical and materials science applications. The majority of such compounds are based on polyesters and polyamides. In contrast, their phosphorus-containing counterparts are much less studied, in spite of their potential precise degradation profile and biocompatibility. Herein, the first library of poly(phosphorodiamidate)s (PPDAs) with two P-N bonds forming the polymer backbone and a pendant P-OR group is prepared through acyclic diene metathesis polymerization. They are designed to vary in their hydrophilicity and are compared with the structural analogues poly(phosphoester)s (PPEs) with respect to their thermal properties and degradation profiles. The degradation of PPDAs can be controlled precisely by the pH: under acidic conditions the P-N linkages in the polymer backbone are cleaved, whereas under basic conditions the pendant ester is cleaved selectively and almost no backbone degradation occurs. The PPDAs exhibit distinctively higher thermal stability (from thermogravimetric analysis (TGA)) and higher glass transition and/or melting temperatures (from differential scanning calorimetry (DSC)) compared with analogous PPEs. This renders this exotic class of phosphorus-containing polymers as highly promising for the development of future drug carriers or tissue engineering scaffolds.

Hot melt extrusion versus spray drying: hot melt extrusion degrades albendazole

The purpose of this study was to enhance the dissolution properties of albendazole (ABZ) by the use of amorphous solid dispersions. Phase diagrams of ABZ–polymer binary mixtures generated from Flory–Huggins theory were used to assess miscibility and processability. Forced degradation studies showed that ABZ degraded upon exposure to hydrogen peroxide and 1 N NaOH at 80 °C for 5 min, and the degradants were albendazole sulfoxide (ABZSX), and ABZ impurity A, respectively. ABZ was chemically stable following exposure to 1 N HCl at 80 °C for one hour. Thermal degradation profiles show that ABZ, with and without Kollidon® VA 64, degraded at 180 °C and 140 °C, respectively, which indicated that ABZ could likely be processed by thermal processing. Following hot melt extrusion, ABZ degraded up to 97.4%, while the amorphous ABZ solid dispersion was successfully prepared by spray drying. Spray-dried ABZ formulations using various types of acids (methanesulfonic acid, sulfuric acid and hydrochloric acid) and polymers (Kollidon® VA 64, Soluplus® and Eudragit® E PO) were studied. The spray-dried ABZ with methanesulfonic acid and Kollidon® VA 64 substantially improved non-sink dissolution in acidic media as compared to bulk ABZ (8-fold), physical mixture of ABZ:Kollidon® VA 64 (5.6-fold) and ABZ mesylate salt (1.6-fold). No degradation was observed in the spray-dried product for up to six months and less than 5% after one-year storage. In conclusion, amorphous ABZ solid dispersions in combination with an acid and polymer can be prepared by spray drying to enhance dissolution and shelf-stability, whereas those made by melt extrusion are degraded.

Graphene oxide embedded P(4‐VP) cryogel composites for fast dye removal/separations

In this study, graphene oxide (GO) prepared via modified Hummers method was embedded within superporous poly(4‐vinylpyridine) (p(4‐VP)) cryogels during the p(4‐VP) cryogel preparation up to 50 wt%. The SEM images revealed that GO layers are embedded within superporous of p(4‐VP) network. The FT‐IR and TGA analysis were also disclosed that the introduction of GO provided new functional groups and new thermal degradation profile for p(4‐VP)/GO cryogel composites. The swelling of p(4‐VP) and p(4‐VP)/GO cryogel composites in different solvent demonstrated that the swelling properties of p(4‐VP) cryogels were highly depend on the solvent and to the existence of GO. Moreover, bare p(4‐VP) cryogel and p(4‐VP)/GO cryogel composites were tested successfully in the direct removal of organic dyes such methylene blue (MB), rhodamine 6G (R6G), and methyl orange (MO) in aqueous environment. Interestingly, it was further illustrated that the separation of MB, R6G, and MO from their mixtures can be accomplished readily by using these cryogels as filter materials. The protonated forms of p(4‐VP), p(4‐VP)/GO that were obtained by HCl treatment of these cryogel systems were shown to be very successful in the separation of these dye mixtures. POLYM. COMPOS., 39:1694–1703, 2018. © 2016 Society of Plastics Engineers

Thermal Decoating of Aerospace Aluminum Alloys for Aircraft Recycling

Recycling of aircraft aluminum alloys can be complex due to the presence of their corrosion protection coating that includes inorganic compounds containing Cr(VI). In this study, the characterization and thermal degradation behavior of the coating on aluminum substrates coming from an aircraft destined for recycling are presented. Elements such as Sr, Cr, Si, Ba, Ti, S, C, and O were found in three different layers by EDS elemental mapping corresponding to SrCrO4, Rutile-TiO2, SiO2, and BaSO4 with an overall particle size D 50 = 1.96 µm. The thermal degradation profile analyzed by TGA showed four different stages. The temperature of complete degradation at the fourth stage occurred at 753.15 K (480 °C) at lower heating rates. At higher heating rates and holding an isotherm at the same temperature, the residence time to fully decompose the aircraft coating has been estimated as 4.0 ± 0.2 minutes. The activation energy calculated by the Flynn–Wall–Ozawa and the modified Coats-Redfern methods for multiple fraction of decomposition showed a non-constant behavior indicating the complexity of the reaction. Finally, the concentration of Cr(VI) released to the environment during thermal decoating was obtained by UV–Vis spectroscopy. It was found that 2.6 ± 0.1 µg of Cr(VI)/mm2 of aluminum substrate could be released unless adequate particle controls are used.