Stages Of Thermal Degradation Research Articles

Extraction and characterization of Bougainvillea glabra fibers: A study on chemical, physical, mechanical and morphological properties

Bougainvillea glabra fibers (BGFs) present a promising avenue for sustainable material development owing to their abundance and favorable properties. This study entails a thorough investigation into the composition, physical characteristics, mechanical behavior, structural properties, thermal stability, and hydrothermal absorption behavior of BGFs. Chemical analysis reveals the predominant presence of cellulose (68.92 %), accompanied by notable proportions of hemicellulose (12.64 %), lignin (9.56 %), wax (3.72 %), moisture (11.78 %), and ash (1.75 %). Physical measurements ascertain a mean fiber diameter of approximately 232.63 ± 8.59 μm, while tensile testing demonstrates exceptional strength, with stress values ranging from 120 ± 18.26 MPa to a maximum of 770 ± 23.19 MPa at varying strains. X-ray diffraction (XRD) elucidates a crystalline index (CI) of 68.17 % and a crystallite size (CS) of 9.42 nm, indicative of a well-defined crystalline structure within the fibers. Fourier-transform infrared spectroscopy (FTIR) confirms the presence of characteristic functional groups associated with cellulose, hemicellulose, wax, and water content. Thermogravimetric analysis (TGA) delineates distinct thermal degradation stages, with onset temperatures ranging from 102.76 °C for water loss to 567.55 °C for ash formation. Furthermore, hydrothermal absorption behavior exhibits temperature and time-dependent trends, with absorption percentages ranging from 15.26 % to 32.19 % at temperatures between 30 °C and 108 °C and varying exposure durations. These comprehensive findings provide essential insights into the properties and potential applications of BGFs in diverse fields such as bio-composites, textiles, and environmentally friendly packaging solutions.

Thermal Degradation Kinetic Study of Expanded Perlite‐Modified Butadiene Rubber Composites

AbstractMineral–rubber composites based on phosphorylated butadiene rubber (PhBR), including pure expanded perlite (EP) and modified phosphorylated expanded perlite (PhEP) as fillers, are developed. The process involves forming PhBR and its composites—EP/PhBR and PhEP/PhBR—through the oxidative chlorophosphorylation (OxCh) reaction. An in‐depth comparative analysis is conducted on the thermal destruction of the PhBR matrix and the EP/PhBR, and PhEP/PhBR composites. The thermogravimetric (TG)/differential thermogravimetry (DTG) analyses reveal three stages of thermal degradation for the PhBR matrix and both composites, highlighting the notable effects of EP and PhEP in the second and third stages of the degradation process. In comparison, the PhEP/PhBR composite exhibits reduced weight loss, the highest integral procedural decomposition temperature (IPDT) value, and a lower Tmax on the DTG curve, compared with the EP/PhBR composite and the PhBR matrix. The mechanism of the thermal destruction reaction and the kinetic parameters Ea and A are calculated using the model‐fitting Coats–Redfern method.

Fabrication of geopolymer composites using egg-shell and fly-ash: Comparison between the strength and stability, physio-chemical and mechanical properties

Nowadays, the demand for developing new structural materials, particulate composites made from industrial waste has been preferred along with conventional fiber-reinforced composites. In this work, two new composites were fabricated by reinforcing flyash and eggshell separately in epoxy with equal volume fractions and were termed geopolymer composites. Further thermo-mechanical characterization of these fabricated geopolymer composites was carried out by conducting various mechanical, physical, chemical, and thermal testing methods. The results were compared with the outcomes of neat epoxy composites. It was demonstrated that eggshell-epoxy composites have 28.48 % and 1.5 % more tensile strength than neat epoxy and flyash-epoxy composites. The flexural strength and hardness in a similar fashion were observed as increased by 31.7 %, 7.37 %, and 29.45 %, 15.6 % over neat epoxy and flyash-epoxy composites. The composites were crystalline confirmed from the XRD analysis. In contrast to the above, the thermal conductivity and thermal stability of flyash-epoxy composites were found superior though eggshell-epoxy composite visualized higher stability at the initial stage of thermal degradation. Further, the change of thermal conductivity of these materials with a temperature change was investigated by finite element modeling in MATLAB using the PDE toolbox. It was examined that thermal conductivity increases non-linearly with the increase in temperature up to 700 °C and then follows a uniform trend on further increase.

Kinetic Analysis of Thermal Decomposition of Polyvinyl Chloride at Various Oxygen Concentrations

PVC plastic products are common combustible substances seen in fires, but their thermal degradation behavior under different oxygen concentrations has not been adequately studied. The thermal degradation behavior of PVC materials in atmospheres with different oxygen concentrations was analyzed via thermogravimetric–Fourier transform infrared spectroscopy (TG-FTIR). The TG results show that the thermal degradation process of PVC under a non-oxygenated atmosphere occurred in two stages, and the activation energies of the two stages were 130–175 KJ mol−1 and 230–320 KJ mol−1, respectively; under the oxygenated atmosphere, the thermal degradation process occurred in three stages. The activation energies of the three stages were 130–175 KJ mol−1, 145–510 KJ mol−1 and 75–190 KJ mol−1, respectively. And the reaction mechanism of the second stage of thermal degradation was changed from D-ZLT3 to En by the higher oxygen concentration. Infrared spectroscopy (FTIR) was used to analyze the pyrolysis process of PVC in the non-oxygenated atmosphere, and the eight major components were as follows, in descending order according to amount released: C-H stretching > HCl > C-Cl stretching > H2O > CO2 > C-H bending > C-H aliphatic bending > CH2. For the reaction of PVC at an oxygen concentration of 7%, the nine major components, in descending order according to amount released, were as follows: CO2 > HCl > H2O > CO > C-H stretching > C-Cl stretching > C-H aliphatic bending > C-H bending > CH2. For PVC reactions at oxygen concentrations of 14% and 21%, the five major components, in descending order according to amount released, were CO2 > HCl > CO > C-Cl stretching > H2O.

Biotechnological investigation of Pediastrum boryanum and Desmodesmus subspicatus microalgae species for a potential application in bioenergy

The production of photosynthetic microalgae is a promising ecological advantage for obtaining carbon credits. This paper addresses cultivation and preparation, growth analysis, physicochemical characterization (X-ray diffraction-XRD, Fourier transform infrared-FTIR, scanning electron microscopy-SEM, and energy dispersive spectroscopy-EDS), and thermal behavior (thermogravimetry-TG, derivative thermogravimetry-DTG, and differential scanning calorimetry-DSC) of two microalgae, namely Pediastrum boryanum-PB (CH007) and Desmodesmus subspicatus-DS (AEE431E) for a potential application as an energy resource. Regarding the former, the literature reports no specific study on the species, which shows high lipid productivity and fast growth. A synthetic culture medium (Walter culture-WC) was subjected to variations in pH, luminosity, and maximum growth reached in 12 and 13 days for PB and DS, respectively. TG/DTG curves identified the main thermal degradation stages, i.e., dehydration (DS (24.68–158.68 °C) and PB (20.06–116.18 °C)), devolatilization (DS (166.34–543.00 °C) and PB (128.22–493.93 °C)), and gasification or carbonization (DS (>550 °C) and PB (>500 °C)), and DSC curves revealed two endothermic events, an exothermic one for DS, and only one endothermic event and an exothermic one for PB. XRD patterns showed a cellulose crystallinity index (CI) for DS (22.54 %) and PB (28.82 %), confirming the predominance of amorphous regions. SEM images detected external epidermis for DS and some interconnected pores for PB. The FTIR spectra identified functional groups (lipids, proteins, and carbohydrates) and CO, CO, OH, CH, and C-O-C linkages, and EDS and ICP-OES identified the main organic, inorganic, and metallic elements. The microalgae species displayed characteristics similar to those of the other biomasses in the bioenergy industry, enabling their use in thermoconversion processes for biofuel production and considering some socioenvironmental aspects.

Synthesis, structure, and optical studies of nanocomposites based on copoly (arylidene cyclohexanone) and CdS nanoparticles for photocatalytic and white LED applications

For various optical applications, the fabrication of nanocomposites of co-polyarylidene (cyclohexanone/4-tertiary butyl cyclohexanone) CoP6 with various-sized cadmium sulfide CdS nanoparticles via in situ polymerization has been investigated (CoP6-CdS NCs). Several techniques like FT-IR, XRD, XPS, SEM, TGA, TEM, UV–vis, and fluorescence emission have been used to investigate, characterize, and study nanocomposites' structural and optical characteristics. The optical band gap of NCs was found to have a slight redshift, from 2.81 to 2.71 eV, with no alteration to the absorption peak. The crystallinity and phase formation were studied by XRD, which showed that the produced NCs with larger (CdS) particles retain some crystalline structure. The NCs generated were characterized by SEM and TEM, revealing their aggregation inside the polymer matrix. The thermal stability of the produced nanocomposites varies with the size of the nanoparticles, with larger NPs being less stable than CoP6 in the first two stages of thermal degradation and smaller NPs showing better stability in the first stages. Their outstanding optical properties make them be used in solar cells and photocatalysts. According to the photophysical analysis, new CoP6-CdS NCs have excellent optical quality with 95% optical transparency and low absorption in the visible region; the light transmittance in the UV region is reduced as the size of the CdS NP increases. There is a potential for using CoP6-CdS NCs in white LED applications in the visible region by varying CdS nanofiller size. However, because the nanocomposites exhibit enhanced absorption in the UV region, they can be used as a material for UV protection.

Vinylester-glass fiber composite for water pipe: Processing and effect of fiber direction

Vinylester-glass fiber composites have a wide scale of applications, however the combination between multiple fillers can cause some disadvantages due to complicated processing, high cost and incompatibility. This paper presents a novel trial for filling commercial vinylester (VE) resin with glass fiber (GF), as one filler component, in dual directions to prepare water pipe composite using the continuous winding technique, for the first time. 10% to 25% VE-GF composites were prepared with distributing GF in axial and hoop directions. The composites were cured via in-situ polymerization; the crosslinked network is occurred between catalyst and unsaturation sites in prepolymer. All concentrations show stability in all stages of thermal degradation, compared with blank VE; the more stable composite is 25% VE-GF. GF filled in axial and hoop directions enhanced the mechanical strength of both axes. The improved concentration (20% VE-GF composite) increased axial tensile strength and hoop tensile strength respectively to 32 MPa and 51 MPa, compared with 22 MPa and 42 MPa for blank VE. Furthermore, this concentration enhanced the strengths of surface harness and pull off from 39 BHC and 2.2 MPa to 46 BHC and 5.3 MPa, respectively. The 25% VE-GF composite decreased these values, but still higher than blank. GF improved the resistance of vinylester toward water absorption in different immersion conditions, especially the 25% VE-GF composites. The filling direction doesn’t affect the composite stability. As a key issue for sustainable applied polymer composites, the proposed technique presents stable and low cost composite with one filler type, as physically, thermally and mechanically stable water pipe system.

Photocatalytic Activity and Thermal Stability of Hybrid Metal-Polymer-Coordinated Complexes Derived from Gallic Acid and Ethylenediamine.

Three new hybrid metal-polymer-coordinated complexes (MPCs) of copper(II), cobalt(II), and nickel(II) ions with an organic polymer derived from gallic acid and ethylenediamine (GAEtH) were synthesized. The structures of GAEtH and MPCs were characterized with FT-IR, ultraviolet (UV)-Vis, 1H and 13C NMR spectroscopy, and elemental and thermogravimetric analysis. The results reveal that the organic polymer GAEtH exhibits an infinite one-dimensional chain structure, while the hybrid MPCs have a double chain structure, with the two chains joined by metal ions. The thermodynamic and kinetic parameters of the thermal degradation stages were determined by the Coats Redfern method, and the photocatalytic behaviors of the MPCs were investigated through the decomposition of methyl orange dye under UV irradiation.

Dressings produced from PVA nanofibers containing chloramphenicol

In this study, electrospun PVA membranes crosslinked with citric acid or glutaraldehyde and containing the antibiotic chloramphenicol (CLF) were obtained for the production of dressings. This material was characterized by SEM, FTIR, DSC, TGA NMR, degree of swelling, and solubility. The SEM images showed the possibility of obtaining nanofibers with a diameter between 600 and 700 nm. Crosslinking with citric acid (3% m/m) was the only one able to give stability to PVA fibers in water and preserve their morphology. The stability of PVA fibers in water was associated with a decrease in OH groups in PVA and an increase in crystallinity, both effects promoted by crosslinking. The increase in crystallinity due to crosslinking was observed by DSC, DRX, and FTIR analyses. A linear correlation was found between the increase in enthalpy of fusion and the increase in crystallinity. The FTIR analysis confirmed the incorporation of the drug into the fibers. The results of TGA analysis suggested that the presence of basic groups in the CLF molecule may act as proton receptors delaying the first stage of thermal degradation of the polymer. The absence of CLF-related peaks in the X-ray diffractograms and DSC curves suggests that the drug may be in an amorphous state, which improves the solubility of CLF and facilitates its immediate release, making the drug more bioavailable. The mechanism of CLF release indicated that the kinetics follows the typical Weibull model for matrix systems, showing an immediate release in the first 30 min. The membranes exhibited hemotoxicity below the limit established by ASTM F756–08. In addition, the disk diffusion tests showed antimicrobial activity against S. aureus, S. epidermidis, and P. aeruginosa strains, indicating that these membranes are promising for use in wound dressings with anti-infective biological activity.

Effects of organically-modified montmorillonite and alkalinization on physical, mechanical, chemical, morphological, and thermal properties of wheat straw/recycled polypropylene nanocomposites

Valorization of wheat straw fiber/recycled polypropylene nanocomposites was investigated through studying the individual and combined effects of organically modified montmorillonite (OMMT) and alkali treatments on the given composites. FTIR spectra indicated the reduction of wheat straw fibers' hydroxyl groups due to hemicellulose removal resulting from alkali treatment. There were also trace diminutions in C-O peak intensities due to the degradation of little amounts of lignin. X-ray analysis revealed the intercalation of nanoclay in the polymer matrix. The improved interaction of fiber-polymer interfaces brought about by alkali treatment was also confirmed by scanning electron microscopy. The water absorption and thickness swelling properties of the nanocomposites were improved due to the barrier properties of nanoclay against water ingress. The flexural strength and modulus of elasticity increased by the individual, and likewise combined treatments. Thermogravimetric analysis demonstrated that the temperatures of first and second stages of composites' thermal degradation increased via the formation of a carbonized char layer thermally insulating the deeper composite layers. Differential scanning calorimetry showed some slight increases in the melting temperature, melting enthalpy, crystallisation temperature, crystallisation enthalpy, and crystallinity index of the treated composites due to the nucleating effect of nanofillers. The overall results showed that the combined treatment of OMMT and NaOH (vs. the individual ones) could significantly improve the overall properties of the studied composites. This was due to some interesting synergistic effects of the given treatments converting the wheat straw fiber/recycled polypropylene nanocomposites to high performance materials of choice for industry.

Study on high moisture extruded pea protein isolate based on acid-induced process: Physicochemical properties, conformational changes and fibrous structure mechanism

The present study aims to gain a better understanding of the physicochemical properties and quality attribute changes, and fibrous structure formation mechanisms of pea protein analogs with different glucan-δ-lactone (GDL) additions under high moisture extrusion. The results showed that the pH value of the extrudates gradually approached the isoelectric point and the zeta potential increased with the increase in GDL, which reduced the water holding capacity, nitrogen solubility index and browning index values, while increasing the hardness, chewiness and fibrous degree of the extrudates. The comparison revealed the maximum zeta potential value and total SH, and minimum free SH of the raw material, suggesting the unfolding and cross-linking of proteins under the triple action of the extruder. The relative content of β-sheet as the predominant component of protein extrudate decreased, while α-helix increased, and λmax was bathochromiclly shifted through FTIR and fluorescence spectroscopy. However, negative trends were observed when the GDL concentration reached 1%, due to the excessive concentration of the GDL accelerating the aggregation and sedimentation of proteins, and intensified the phase separation degree in the cooling die during the extrusion process, thus promoting the change in the velocity gradient. In addition, the thermal stability of the extrudate first increased and then decreased as the GDL concentration increased, and showed a three-step thermal degradation stage. The pores and highly irregular fibrous filaments transformed into a highly compact and coarse matrix with an excessive GDL concentration, as observed by SEM. These findings validate the potential of GDL to improve the textural attributes and structure formation of meat analogs, and provide a reference for the development of acid-induced proteins under high moisture extrusion.

Valorization of the biomass of Rhizoclonium hookeri through slow pyrolysis and its thermokinetic investigation for bioenergy potential

The macroalgae, Rhizoclonium hookeri has the ability to grow in fresh and wastewater rich in nutrients like phosphorus and nitrogen. Here we have performed the slow pyrolysis of dried R. hookeri at three different thermal rates of 5, 10 and 20 °C min−1 from 25 to 800 °C using the thermogravimetric technique to get the thermokinetics for its bioenergy value. Four different thermal degradation stages were considered to get the kinetic triplets from its pyrolysis. The activation energy was obtained for each stage of thermal decomposition utilizing four classical isoconversional methods (Friedman, Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, and Starink). The activation energies obtained through these isoconversional methods for the four valorization zones of R. hookeri were in the range of 151.15–192.62 kJ mol−1. The pre-exponential factor (A) showing the chemical nature of each reaction step was extracted from the kinetic compensation effect and has values in the range of 1.99 × 1020 to 2.63 × 1012 min−1. The thermodynamic parameters revealed the non-spontaneous, endothermic and complex nature of the pyrolysis process of Rhizoclonium biomass. The thermokinetic data showed that Rhizoclonium biomass has bioenergy potential like other macroalgae and is a suitable feedstock for the large-scale pyrolysis process. In conclusion, the outcomes from this study suggest the suitability of Rhizoclonium hookeri as a feedstock for producing bioenergy and is of great significance for designing large-scale equipment to pyrolyze this macroalgal specie.

Comprehensive Characterization of Cocos nucifera Palm Residues for Biochar Production

The feasibility of using Cocos nucifera palm residues such as shell, husk, leaflets, fronds, and rachis for biochar production was investigated. Biomass characterization such as proximate, elemental, biochemical, higher heating value, and thermogravimetry were analysed. The results showed that fixed carbon of coconut palm residues was in the range of 10.48% to 17.47%, with the shell being the highest. Carbon, hydrogen, nitrogen, and oxygen content of the residues ranged from 39.46% to 48.60%, 4.23% to 6.00%, 0.42% to 1.66%, and 44.98% to 55.28%, respectively. Among the residues, lignin content was found to be maximum in the shell biomass (29.31%) and minimum in the rachis (21.89%). Thermogravimetric analysis of coconut palm residues revealed the presence of three stages of thermal degradation with overall weight loss ranging between 68.56% and 77.08 per cent. Higher fixed carbon and lignin content unveiled the potential of coconut palm residues for biochar synthesis. Slow pyrolysis of coconut palm residues resulted in biochar generation with fixed carbon content ranging between 65.40% and 78.21%, and proved its suitability for applications such as solid fuel, adsorbent, catalyst, and precursor for biomaterials production such as activated carbon and carbon molecular sieves.

Removal of Cu (II) Ions from Aqueous Solution Using Poly-Amidoxime Resin from Grafted Millet Husk Cellulose

Poly-amidoxime ligand was synthesized on the cellulose isolated from millet husk through a graft copolymerization process for adsorption of Cu (II) ion from aqueous solution. The functional group, thermal degradation and morphology of the adsorbent were investigated by Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA) and scanning electron microscope (SEM), respectively. The FTIR results showed that grafting was successful due to the presences of 2244 cm-1 for cyano group (CN) and also band at 1640 cm-1 and 1380 cm-1 that replaced 2244 cm-1 which successfully confirmed the synthesis of poly(amidoxime) functional group. The TGA showed two stages of thermal degradation 12 % weight loss observed in amidoxime at 240 0C which is due degradation of amidoxime functional group then it reduces to 2% in second stage at 530 0C which revealed the improved thermal stability of the material. The SEM image showed a clear morphology of the absorbent before adsorption and after adsorption. The Initial concentration, adsorbent dosage and contact time were taken as independent variables. The adsorption process was optimized by central composite design (CCD) in Response surface methodology (RSM). The predicted value is in good agreement with experimental value and also the ANOVA result showed that all the independent variables have significant impact with the adsorbent. The optimum condition achieved in the experiment was at initial concentration of 150 mg/L, adsorbent dosage of 0.3 g and contact time of 90 min for Cu2+ with percentage removal of 55.41 % predictably and 54.92 % experimentally.

Effect ofCaSt2/ESOthermal stabilizers on the preparation, thermal stability, and thermal stability mechanism of self‐made vinylidene chloride‐methyl acrylate copolymer resin film

AbstractThe effects of heat stabilizer systems on the thermal stability and processability of self‐made vinylidene chloride‐methyl acrylate copolymer (PVDC‐MA) film were investigated via accelerated aging test, Congo red test, FTIR, DMA, and TG‐FTIR. These results displayed that CaSt2/ESO performed excellently in synergistic inhibition of PVDC‐MA thermal degradation. Especially, when the mass ratio of CaSt2/ESO was 1.5:1.5, the static thermal stability time of PVDC‐MA was increased from 14.5 to 46.5 min. The kinetic calculation results also verified this point. Compared with pure PVDC‐MA, the average apparent activation energy (Ēa) of thermal degradation reaction of PVDC‐MA stabilized by CaSt2/ESO enhanced from 144.1 to 169.7 kJ mol−1(α0 ≤ 0.1), indicating that the thermal stability of PVDC‐MA in the initial thermal degradation stage was dramatically improved by CaSt2/ESO. Moreover, the mechanism of the effect of CaSt2/ESO on PVDC‐MA in the initial thermal degradation stage was further explored by the generalized master plot methods. The kinetic analysis result suggested that under the synergistic effect of CaSt2/ESO, the mechanism model followed by the degradation of PVDC‐MA changed essentially (the three‐dimensional diffusion thermal degradation mechanism transformed into two‐dimensional diffusion).

Kinetic study of the thermolysis process of oil sludge (atasu-alashankou) with nickel, cobalt and iron deposited on microsilicate

The object of research is the process of thermal degradation of oil sludge in the presence of heterogeneous catalysts. The creation of efficient technological processes for processing the organic part of oil sludge into motor fuels, raw materials for petrochemicals and the disposal of microsilicate is an important urgent task, the solution of which will allow to obtain a significant economic and environmental effect. The problem to be solved is to establish the general kinetic laws of the process of thermal degradation of oil sludge in the presence of microsilicate with deposited metals. The advantage of the Ozawa– Flynn–Wall method is that it is possible to determine the kinetic parameters for each value of oil sludge conversion, that is, for different stages of thermal degradation. The activation energy of oil sludge 67.1 kJ/mol, and with a catalyst 59 kJ/mol are calculated for each degree of conversion (α), respectively. The value of the correlation coefficient was (R2≥0.997) provides good convergence with experimental results. Compared with other methods of thermal processing of oil sludge, catalytic thermal degradation has a number of advantages: relatively low process temperatures (400–650 °C), low sensitivity to the composition of raw materials and the processing process, which meets all modern requirements of chemical production. Regularities of thermokinetic parameters of thermal decomposition of oil sludge were studied using raw materials obtained during the process of oil transportation, in the presence of catalyst with applied metal (nickel, iron, cobalt) to microsilicate. Obtained results of oil sludge decomposition kinetics can be used in creating a database for mathematical modeling of process of heavy hydrocarbon raw materials processing

The development of eco‐friendly UV‐protective polyacrylate/rutile TiO2 coating

AbstractThis work aims to prepare a coating with good UV protection properties while maintaining optimal transparency. In this work, the addition of 0–2 wt.% TiO2 on the properties of polyacrylate (PA), the method of preparation, and the effect of UV exposure on coatings were investigated. Rutile TiO2/PA coatings were prepared by ex situ and in situ emulsion polymerization. The results showed that the addition of nanoparticles and the preparation method significantly affect the particle size distributions of PA, such that ex situ emulsions show the presence of agglomerates, while they are not visible in in situ emulsions. Viscosity also depends on the preparation method, so ex situ emulsions show no change with the addition of nanoparticles, while in situ emulsions show an increase in viscosity. In situ coatings also have better morphology and transparency compared to ex situ. The addition of nanoparticles increases the thermal stability of PA in the later stages of thermal degradation and causes a decrease in tensile strength with an increase in elongation at break of PA. In situ coatings also provide better UV protection properties compared to ex situ coating films.

Biodegradation of novel bioplastics made of starch, polyhydroxyurethanes and cellulose nanocrystals in soil environment

Plastic pollution is recognized as a major environmental problem in many countries. Over the last decade, academics have embraced research on bioplastics to discover newer high-end green materials. However, the end-of-life environmental fate of such materials is not adequately understood. Non-isocyanate polyhydroxyurethanes (PHUs) are green engineering materials with huge potential to replace traditional polyurethanes. Despite this immense potential, a number of questions about their environmental fate remain unanswered. The present study investigated the extent and mechanisms underlying soil biodegradation of PHUs and determined whether the deterioration of PHUs within starch bioplastics (ST) can improve the biodegradation of starch (ST)-PHU hybrids. Soil microbiomes managed to effectively and quickly digest not only PHUs but also ST-PHU hybrids. All ST-PHU hybrids were characterized by exceptional biodegradability with mass losses of up to ~88% following a soil burial time of only 120 days. The biodegradation of ST-alone bioplastics was 69% under identical conditions. The presence of cellulose nanocrystals (CNC) reduced the potential for the soil microbial community to degrade nanohybrids (ST-PHU-CNC). Microbially digested bioplastics with PHU presented less stages of thermal degradation, and reduced intensities of FTIR, NMR and XPS signals compared to the original films, indicating improvement of the biodegradation mechanism. These findings suggested the positive environmental implications of PHU in improving the bioplastic's degradation and their potential for future applications.

New nickel (II), cobalt (III), and iron (III) complexes with N′‐[(2‐aminochromon‐3‐yl)methylidene]benzohydrazide: Synthesis, characterization, solvatochromic shift, dipole moment, and DFT calculations

AbstractNew Ni (II), Co (III), and Fe (III) complexes of hydrazone (HL) derived from 2‐aminochromone‐3‐carboxaldehyde with benzoyl hydrazine were synthesized and characterized by elemental analyses, spectral (UV–Vis, IR, Mass, 1H, and 13C‐NMR) data, as well as magnetic susceptibility, molar conductivity measurements, and thermal gravimetric analysis (TGA). The ligand behaves as monobasic with ONO donor sites, forming square planar geometry with Ni (II) and octahedral geometries with both Co (III) and Fe (III) complexes. Solvent effects on the absorption and fluorescence spectra of the prepared complexes were investigated in 11 different solvents with diverse polarities. Lippert–Mataga, Bakhshiev, Kawski–Chamma–Viallet, and Reichardt‐solvatochromic methods were applied to estimate the dipole moments of the ground and excited state (μg and μe). Multiple linear regression analysis was useful to specify the extent of specific and nonspecific solute–solvent interactions using Kamlet–Taft and Catalan solvatochromic models. The Stoke's shifts of complexes were mainly controlled by the polarity/polarizability parameter of the solvent. Density function theory (DFT) at B3LYP/6‐311G(d,p) level engaged in the Gaussian 09 program was carried out to optimize the structures of the ligand and its complexes. Structural parameters data are correlated with the experimental data. Also, using Coats–Redfern techniques, the kinetic parameters were calculated for each thermal degradation stage of metal complexes. Finally, in vitro bioassays of the ligand and its complexes against Gram‐negative, Gram‐positive bacteria and the fungus strain were tested for these compounds with good results.

Modeling and evaluation of dynamic degradation behaviours of carbon fibre-reinforced epoxy composite shells

In this study, a segmented degradation model was established for the first time to predict and evaluate the dynamic degradation characteristics of carbon fibre-reinforced epoxy composite (CFRC) shells accurately by considering temperature variations during heating, maintenance, and cooling. The model is based on the Reddy's high-order shear deformation theory, complex modulus method, and coefficient fitting approach. First, explicit expressions of material parameters and thermal expansion coefficients (TECs) in different thermal degradation stages were proposed, followed by the derivation of the differential equations to solve the structural dynamic degradation characteristics. Moreover, an identification method for the fitting coefficients of the CFRC material was described, which is based on experimental tests and iterative calculations of elastic moduli, loss factors, and TECs at different degradation time points in different thermal degradation stages. Finally, the natural frequencies, damping ratios, and time-domain responses were measured using a novel testing system for the dynamic degradation of specimens subjected to a pulse excitation load to validate the developed model. Theoretical and experimental results indicate that the natural frequencies decreased as the degradation time increases at the heating-up and temperature maintenance stages, whereas they increased at the cooling stage. However, an uptrend in the damping and response behaviours was observed in the first two stages, whereas a downtrend was recognized at the cooling stage.