Thermal Degradation Steps Research Articles

Thermal and toughness enhancement of poly (lactic acid) bio-nanocomposites

Bio-nanocomposites based on poly (lactic acid)/epoxidized natural rubber (PLA/ENR) blends containing graphene (G) nanofiller were prepared by melt compounding using nano-single screw extruder with a screw speed of 60 rpm, and followed by compression molding. The ENR and graphene loading was varied from 0-30 wt% and 0.5-2.0 phr. The objectives of this work are to investigate the effect of ENR and graphene loading on PLA matrix on the thermal, morphology and toughness properties. The TGA curve of PLA/ENR and PLA/ENR/G bio-nanocomposites shows a single step of thermal degradation. As increasing the loading of graphene, degradation temperature (Tdeg) was increase where graphene act to slow down the rate of degradation. The PLA/ENR blends showed a co-continuous morphology while PLA/ENR/G bio-nanocomposites revealed a good dispersion of graphene in a PLA/ENR matrix at 1 phr of graphene loading. The optimum impact strength was recorded at 10 wt% of the ENR loading which is 104.6 J/m for the PLA/ENR system. In the case of PLA/ENR/G system, the optimum impact strength was recorded at 1 phr of graphene which is 219.5 J/m. The thermal and toughness enhancement of PLA/ENR/G bio-nanocomposites will diversify the future application of this bio-nanocomposites.

Thermal degradation of oriental beech wood impregnated with different inorganic salts

This study investigated the thermal properties of Oriental beech (Fagus orientalis) treated with (NH4)2HPO 4, K2HPO4, NH4Cl and (NH4)2SO4 salts and their mixtures (1:1; w/w) aqueous solutions at 3% concentrations. The effects of different inorganic salts fire retardants on the thermal degradation characteristics of wood samples were evaluated by thermogravimetric analysis (TGA). Based on the TGA curve for untreated beech wood, weight loss takes place at three distinct steps. The impregnation of inorganic salts resulted in higher char yields and additional thermal degradation steps were identified. The highest char yield (80%) was obtained from (NH4)2HPO4-K2HPO4 mixture impregnated sample. Salt mixtures containing phosphates ((NH4)2HPO4 and K2HPO4) have remarkable effects on thermal stability of beech wood, whereas NH4Cl salt lowered the decomposition temperatures and char yield.

Poly(phenylene) synthesized using diels-alder chemistry and its sulfonation: Sulfonate group complexation with metal counter-ions, physical properties, and gas transport

Sulfonated poly(phenylene) (sPP) thermal stability, physical properties, and gas transport characteristics were evaluated as a function of ion-exchange capacity (x = IEC), and counter-ion type (M = H+, Cs+, Na+, Mg2+, and Al3+). Counter-ion substitution with its sulfonated groups produced Δv(SO3-) vibrational shifts that were related to ion type and valence observed using FTIR. Increasing IEC and counter ion complexation strength within sPP led to greater density and reduced fractional free volume (FFV). sPPx-M exhibited a single thermal degradation step greater than 550 °C that decreased with increasing IEC. Unsulfonated poly(phenylene) (PP) had a glass transition at 391 °C, which shifted to 420 °C upon sulfonation. Thermal stability and mechanical properties increased with counter-ion type in the following order: sPP2.5-Cs+ < sPP2.5-Na+ < sPP2.5-Mg2+. However, decreased thermal stability and physical properties were observed using Al3+ as a counter-ion (sPP2.5-Al3+). He, H2, CO2, N2, O2 and CH4 permeability decreased within sPP2.5-M based upon counter-ion type, size, and valence. Larger CO2 and H2 molecules were more permeable than He, which revealed a more complex transport process was occurring within sPP2.5. Metal-ion complexation with sPP2.5 significantly reduced CO2 and H2 permeability. PP possessed high CO2 permeability (152 Barrers) with moderate CO2/CH4 selectivity (12.6). sPP2.5-Na+ (IEC = 2.5 meq/g) had a CO2/CH4 selectivity of 71.3, and counter-ion substitution to create sPP2.5-Cs+ increased CO2/CH4 selectivity by 23%. Gas solubility and diffusivity decreased with increasing IEC and metal-ion complexation strength. sPPx-M had tunable ideal gas permselectivity that was largely a function of sulfonate group concentration and counter-ion type.

TGA investigation and morphological properties study of nanocrystalline cellulose/ag‐nanoparticles nanocomposites for catalytic control of oxidative polymerization of aniline

Polyaniline (PANI) and PANI/nanocrystalline cellulose (NCC)/silver nanoparticles (AgNPs) nanocomposites have been prepared via in situ oxidative polymerization of aniline in the presence of NCC and AgNPs in green mediate using sugar beet leaf extracts. A series of nanocomposites has been synthesized by varying the concentrations of AgNPs (0, 1, 4, and 8%) along with 2 wt% of NCC. The control on oxidative polymerization for aniline has been studied using fabricated nanocomposites as catalysts. Various analysis techniques, including UV‐visible spectroscopy, X‐ray diffraction, and transmission electron microscopy, were adopted to confirm the Nano‐sized AgNPs. The characteristic peaks of PANI and its nanocomposites were observed in the Fourier transfer infrared spectra of the nanocomposites, indicating the incorporation of NCC and AgNPs in the nanocomposite structure. Using three mathematical models, namely, Horowitz–Metzger, Coats–Redfern, and Broido methods, thermal degradation and kinetic parameters of the composites have been calculated for each step of thermal degradation. POLYM. COMPOS., 40:E753–E764, 2019. © 2018 Society of Plastics Engineers

Preparation and characterization of nano‐Sb2O3/poly(butylene terephthalate) composite powders based on high‐energy ball milling

In this work, a kind of composite powders with good dispersion and distribution of nano‐Sb2O3 particles in poly(butylene terephthalate) (PBT) was prepared by the high‐energy ball milling (HEBM). The effects of the milling time on the structure, morphology, particle size distribution, and thermal behavior of the nano‐Sb2O3/PBT composite powders were characterized by Fourier transform infrared spectroscopy, scanning electron microscope, laser diffraction particle size analyzer, and thermal analysis (TGA, DTG and DSC) techniques. The results showed that the regular shape of PBT powders was converted into flakes and the nano‐Sb2O3 particles were well deagglomerated and better dispersed in the PBT matrix during the HEBM process. The mechanochemical activation that was provided by the HEBM process caused a reduction in the molecular weight of PBT, which result in favoring the first step of thermal degradation. Furthermore, two Tg’s were obtained in the case of the nanocomposite powders when the milling time was over 3 h, one of them being slightly higher than that of the pure PBT, which indicated that there was a special interaction between PBT and nano‐Sb2O3 particles. However, the HEBM process leaded to a decreasing of the PBT crystallinity. J. VINYL ADDIT. TECHNOL., 25:91–97, 2019. © 2018 Society of Plastics Engineers

The Influences of Zirconium Dioxide on ENR-25/ZrO2 Composites: FTIR and TGA Analysis

The characterization and thermal stability of purified epoxidized natural rubber with 25 mol% epoxidation (ENR-25) and treated epoxidized natural rubber with 25 mol% epoxidation / Zirconium dioxide (ENR-25/ZrO2) Composites were studied using Fourier transform infrared spectroscopy (FTIR) and thermo gravimetric analysis (TGA). The ENR-25/ZrO2 composites were treated with acetic acid and two different loading (50 and 100 mg) of ZrO2 were used to form the composites. FTIR results show the ester (C-O) peaks at 1000-1300 cm-1 due to the presence of acetic acid in the composites. The disappearance of epoxide peak at range 880-875 cm-1 indicated that ZrO2 have formed hybrid bonds with opened epoxide rings. The both ENR/ZrO2 composites showed 2 major thermal degradation steps (304 - 489°C and 493 – 551°C) for 50 mg ZrO2 loading and (306 - 497°C 512 – 581°C) for 100 mg ZrO2 loading indicating that the thermal stability of the composites have improved.

Insight on the structural aspect of ENR-50/TiO2 hybrid in KOH/C3H8O medium revealed by NMR spectroscopy

The ring-opening reactions (ROR) of epoxide groups in epoxidized natural rubber/titania (ENR-50/TiO2) hybrid in potassium hydroxide/isopropanol medium were examined using NMR spectroscopy and supported by the FTIR technique. The thermal behaviour of the hybrid was also studied using TG/DTG and DSC analyses. The 1H NMR results suggested that 16.82% of ROR occurred in the hybrid, while the 13C NMR results exhibited five new peaks at δ 19.5, 71.0, 73.7, 91.7 and 94.4 ppm in the hybrid. 2D NMR, such as HMQC, HMBC and COSY techniques, further scrutinized these assignments. The FTIR spectrum exhibited Ti-O-C characteristics via the peak at 1028 cm−1. The TG/DTG results showed four steps of thermal degradation at 44–148, 219–309, 331–489 and 629–810 °C due to the existence of Ti moieties along with a polymer chain mixture (intact and ring-opened epoxide groups) of ENR-50, which in turn led to an increase in the Tg value of the hybrid to 27 °C compared to that of purified ENR-50 at −17.72 °C.

Ligational, DFT, optical band gap and biological studies on Mn(II), Co(II) and Ni(II) complexes of ethyl and allyl thiosemicarbazides ending by thiazole group

The Mn(II), Co(II), Ni(II) and Cu(II) complexes with two ligands derived from the addition of 2-(2-aminothiazol-5-yl) actahydrazide to ethyl (H2TAET) and allyl (H2TAAT) isothiocynates have been prepared and characterized by way of traditional strategies. The isolated complexes assigned the formulae, [Mn(HTAET)2(H2O)2](2.5H2O), [Co(HTAET)(H2O)3Cl](2H2O), [Ni(HTAET)(H2O)2Cl](4H2O), [Mn(HTAAT)Cl](2.5H2O), [Co(HTAAT)(H2O)Cl](2H2O) and [Ni(HTAAT)(H2O)Cl]. IR data found out that the both ligands behave as monovalent bidentate via (CN)th and deprotonated enolized (CO) group in Mn(II) and Co(II) complexes of (H2TAET) and in all complexes of (H2TAAT) except Mn(II) complex. Mn(II) of (H2TAAT) and Ni(II) of (H2TAET) complexes act as monobasic tridentate (NNO) and subsequently (H2TAET) act as (NNS) tridentate in Cu(II) complex. The data of UV–vis spectra and the magnetic measurements recommended that the octahedral geometry for all complexes of (H2TAET) at the same time as tetrahedral geometry for all complexes of (H2TAAT) except Ni(II) that is square planar was suggested. The bond lengths, bond angles, HOMO, LUMO and dipole second values have been calculated by way of DFT the use of materials studio program to verify the recommended geometries of ligands and their metal complexes. Additionally, the kinetic and thermodynamic parameters for the different thermal degradation steps of the complexes have been decided by way of Coats-Redfern and Horowitz- Metzger techniques. The optical band gap (Eg) of the metal complexes has been calculated. The optical band gap (Eg) measurements confirmed allowed direct electronic transitions for the photon absorption inside the investigated complexes. Moreover, the antimicrobial, antioxidant and antitumor of ligands and their complexes have been evaluated.

Bentonite/chitosan nanocomposite: Preparation, characterization and kinetic study of its thermal degradation

The nanocomposite 5%Bentonite/Chitosan (5%Bt/CS) has been prepared and characterized by the means of Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Brunauer, Emmett and Teller method (BET). These techniques confirmed the formation of the 5%Bt/CS, via the intercalation of CS in the interlayer space of Bt leading to the exfoliation of its structure. The non-isothermal degradation process of 5%Bt/CS under air atmosphere was investigated by thermogravimetric analysis (TGA/DTG) and differential scanning calorimetry (DSC), at various heating rates. The appearance of multi-peaks in the DTG curves of 5%Bt/CS, revealed that the nanocomposite underwent a complex degradation mechanism with at least two steps, and greater stability compared to those of neat CS. The thermal degradation steps kinetic parameters were calculated using Kissinger (KIS) and isoconversional Flynn–Wall–Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), Tang and Friedman (FR) methods It was found that the average values of activation energies were Ea = 210.53 kJ/mol for the first step and Ea = 345.28 kJ/mol for the second step. These values were used to match the experimental and simulated y(α) and z(α) master plots. It was found that the modified Sestak-Berggren f(α) = c(1 − α)nαmmodel allowed reproducing qualitatively the Y(α) curves, giving the same maximums, αm, for each value of β, which are consistent with the thermal degradation mechanisms of 5%Bt/CS.

Synthesis, thermal studies and conversion degree of dimethacrylate polymers using new non-toxic coinitiators

The aim of this paper is to replace toxic coinitiators (tertiary amines) by non-toxic compounds such as glycerol and inositol (polyalcohol) in dimethacrylate resins. For this purpose, mid infrared spectroscopy (MIR) was used to calculate the monomers' degree of conversion (%DC); as well as simultaneous Thermogravimetric Analysis – Differential Thermal Analysis (TGA-DTA) and Differential Scanning Calorimetry (DSC) were conducted to evaluate thermal stability, degradation steps, and thermal events. The use of different initiator systems did not modify the thermal events or the thermal stability of each of the dimethacrylate resins. Results show a substitution of system 2 (toxicity) by system 3 (low toxicity), which had a good conversion velocity and total conversion in some monomers, is plausible.

Assessment of Physicochemical and Thermal Properties of Energy of Consciousness Healing Treated Ferrous Sulphate Using PXRD, PSD, DSC, and TGA/DTG Analysis

Ferrous sulphate is an inorganic salt of iron used to treat iron deficiency anaemia and maintain the overall health in our body. The current study was designed to evaluate the impact of The Trivedi Effect®-Energy of Consciousness Healing Treatment on the physicochemical and thermal properties of ferrous sulphate using PXRD, PSA, DSC, and TGA/DTG analysis. Ferrous sulphate test item was divided into two parts, one part was considered as control (without Biofield Energy Treatment), whereas the second part received The Trivedi Effect®-Biofield Energy Treatment remotely by the renowned Biofield Energy Healer, Alice Branton. The PXRD data revealed that the relative intensities and crystallite size of the characteristic diffraction peaks in the treated sample were significantly altered from -26.74% to 421.23% and from -24.93% to 42.91%, respectively compared with the control sample. The average crystallite size of the treated sample was significantly increased by 6.39% compared to the control sample. The particle size values at d10, d50, d90 and D(4, 3) values were significantly increased by 30.43%, 35.94%, 19.49%, and 26.26%, respectively and the surface area was significantly decreased by 53.26% compared with the control sample. The melting temperature of the treated sample in the 1st and 3rd peaks was increased by 1.61% and 1.04% respectively, whereas decreased by 5.71% and 1.04% in the 2nd and 4th peaks, respectively compared with the control sample. Consequently, the total latent heat of fusion to transition from FeSO4•7H2O to FeSO4 was decreased by 0.44% in the treated sample compared with the control sample. The TGA thermograms of both the samples exhibited four steps of thermal degradation. The total weight loss in the treated sample was increased by 0.62% compared with the control sample. The maximum thermal decomposition temperature (Tmax) of treated sample was increased by 5.81% and 0.26% in the 1st and 4th peak respectively, but the Tmax of 2nd and 3rd peaks were decreased by 2.58% and 2.38%, respectively compared to the control sample. Overall, DSC and TGA/DTG of the treated sample showed that the thermal stability was changed compared with the control sample. The Trivedi Effect®-Consciousness Energy Healing Treatment might lead to the production of a polymorphic form of ferrous sulphate, which would have better powder flowability and appearance with altered thermal stability compared to the control sample. Alice’s Biofield Energy Treated ferrous sulphate would be useful to design better nutraceutical/pharmaceutical formulations, which could provide better therapeutic response against iron deficiency anaemia.

Solid State Characterization of &amp;lt;i&amp;gt;Withania somnifera&amp;lt;/i&amp;gt; (Ashwagandha) Root Extract After Treatment with Consciousness Energy Healing

Ashwagandha root extract is useful as an herbal medicine and nutraceuticals for the prevention and treatment of various diseases. The aim of the current study was to evaluate the influence of Consciousness Energy Healing Treatment (The Trivedi Effect®) on the physico-chemical, thermal and behavioral properties of ashwagandha root extract using powder X-ray diffraction (PXRD), particle size distribution analysis (PSD), Fourier transform infrared (FT-IR) spectrometry, UV-Vis spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Ashwagandha root extract was divided into two parts – one part was control without any Biofield Energy Treatment, and another part was treated with the Consciousness Energy Healing Treatment remotely by twenty renowned Biofield Energy Healers and defined as Biofield Energy Treated sample. The PXRD analysis concluded that both the control and treated samples were amorphous in nature. The particle size values at d10, d50, and d90 of the treated sample were significantly decreased by 36.78%, 15.18%, and 5.06%, respectively compared with the control sample. Likewise, the surface area of the treated sample was significantly increased by 85.14% compared to the control sample. FT-IR results showed a small impact of Consciousness Energy Healing Treatment on the phytoconstituents of ashwagandha root extract to reduce the force constant of O-H (str.) bond. UV-vis analysis revealed that the wavelength for the maximum absorbance (λmax) of both the samples was at 206.4 in methanol. TGA revealed the three steps of thermal degradation and the total weight loss was decreased by 0.73% in the treated sample compared to the control sample. Consequently, the maximum thermal degradation temperature was found at 272.53°C and 393.35°C for two broad peaks in the treated sample was increased by 0.05% and 0.08%, respectively compared to the control the sample (272.67°C and 393.66°C). The DSC analysis indicated that the evaporation temperature and latent heat of vaporization were lowered significantly by 4.98% and 35.67%, respectively in the treated sample compared with the control sample. The current outcomes suggested that the Energy of Consciousness Healing Treatment might have the amazing capacity to enhance the solubility, dissolution, absorption, bioavailability and thermal stability of ashwagandha root extract in the various form of pharmaceutical and nutraceutical formulation by modifying its particle size and surface area. Thus, the Biofield Energy Treated ashwagandha root extract might provide better therapeutic response against inflammatory diseases, immunological disorders, sexual disorders, arthritis, stress, cancer, ageing, diabetes, and other chronic infections.

Evaluation of the Physico-chemical, Thermal and Behavioral Properties of Ashwagandha Root Extract: Effects of Consciousness Energy Healing Treatment

Withania somnifera (Ashwagandha) root extract has a broad range of pharmacological activities due to the presence of many biologically active metabolites. The current study was designed to evaluate the influence of The Trivedi Effect® - Consciousness Energy Healing Treatment (Biofield Energy Healing) on the physical, spectroscopic, thermal and behavioral properties of ashwagandha root extract using PXRD, PSD, FT-IR, UV-vis spectroscopy, TGA, and DSC analysis. Ashwagandha root extract was divided into two parts – one part was control without any Biofield Energy Treatment and another part was treated with the Consciousness Energy Healing Treatment remotely by twenty renowned Biofield Energy Healers and defined as Biofield Energy Treated sample. The PXRD analysis exhibited that both the control and treated samples were amorphous in nature. The particle size values at d10, d50, and d90 of the treated sample were increased significantly by 8.69%, 7.32%, and 6.50%, respectively compared with the control sample. Similarly, the surface area of the treated sample was significantly decreased by 12.69% compared to the control sample. The FT-IR analysis indicated no significant alteration of the force constant for the functional groups in the treated sample compared to the control sample. The UV-vis analysis revealed that the wavelength for the maximum absorbance of the control and treated samples were at 207.5 and 205.2 nm, respectively. The TGA revealed the two major thermal degradation steps and the total weight loss was decreased by 0.86% in the treated sample compared with the control sample. Consequently, the maximum thermal degradation temperature at 273.53°C and 389.39°C for two broad peaks in treated sample was increased by 0.78% and 0.31%, respectively compared to the control the sample (271.40°C and 388.48°C). The DSC analysis indicated that the evaporation temperature was significantly increased by 10.95% in the Biofield Energy Treated sample with a 5.34% reduced the latent heat of vaporization compared with the control sample. The overall thermal analysis indicated that the treated sample was thermally more stable as compared to the control sample. The Trivedi Effect® - Energy of Consciousness Healing Treatment might lead to have better powder flowability and long-term storage stability compared with the control sample. Thus, the treated ashwagandha root extract might provide better therapeutic response against inflammatory diseases, immunological disorders, stress, arthritis, cancer, diabetes, sexual disorders, ageing, and other chronic infections.

Consciousness Energy Healing Treatment on &amp;lt;i&amp;gt;Withania somnifera&amp;lt;/i&amp;gt; Root Extract and Its Effects on the Physical, Spectroscopic, Thermal and Behavioral Properties

Withania somnifera (Ashwagandha) is useful as an herbal medicine and nutraceuticals for the prevention and treatment of anxiety, insomnia, tuberculosis, tumors, menstrual problems, etc. The objective of the current study was to evaluate the influence of The Trivedi Effect® - Consciousness Energy Healing Treatment on the physical, spectroscopic, thermal and behavioral properties of ashwagandha root extract using PXRD, PSD, FT-IR, UV-vis spectroscopy, TGA, and DSC analysis. Ashwagandha root extract was divided into two parts – one part was control without any Biofield Energy Treatment and another part was treated with the Consciousness Energy Healing Treatment remotely by twenty renowned Biofield Energy Healers and defined as Biofield Energy Treated sample. The PXRD analysis demonstrated that both the control and treated samples were amorphous in nature. The particle size values at d10, d50, and d90 of the treated sample were decreased significantly by 18.88%, 8.60%, and 4.00%, respectively compared with the control sample. Similarly, the surface area of the treated sample was significantly increased by 102.63% compared to the control sample. FT-IR results suggest that there was a small impact of Biofield Energy Treatment on ashwagandha root extract at the atomic level to reduce the force constant of O-H (str.) bond. UV-vis analysis revealed that the wavelength for the maximum absorbance of the control and treated samples were at 207.4 and 207.7 nm, respectively. TGA revealed the three steps of thermal degradation steps and the total weight loss was decreased by 0.13% in the treated sample compared with the control sample. Consequently, the maximum thermal degradation temperature at 272.73°C and 393.14°C for two broad peaks in treated sample was increased by 1.13% and 0.85%, respectively compared to the control the sample (269.68°C and 389.83°C). DSC analysis indicated that the evaporation temperature and latent heat of vaporization was increased by 1.35% and 5.52%, respectively in the treated sample compared with the control sample. The current findings suggested that The Trivedi Effect® - Energy of Consciousness Healing Treatment might have the astounding capacity to enhance the solubility, absorption, dissolution, bioavailability and thermal stability of ashwagandha root extract in various form of pharmaceutical and nutraceutical formulation by modifying its particle size and surface area. Thus, the treated ashwagandha root extract might provide better therapeutic response against inflammatory diseases, immunological disorders, arthritis, sexual disorders, stress, cancer, diabetes, ageing, and other chronic infections.

Synthesis of reduction sensitive comb‐like polyurethanes using click chemistry

ABSTRACTThe synthesis and characterization of new highly biodegradable multipropargyl and comb‐like copolyurethanes have been successfully achieved by the combination of step‐growth polymerization and click chemistry. This work discloses a simple, accurate, and straightforward method to generate brush polymers with an excellent control of the branch nature, distribution, and density in the final materials. The introduction of controlled branching has led to a great variety of polymers, whose hydrophilic/lipophilic characters were adjusted as required. Furthermore, their stiffness, semicrystalline nature, and degradability were fine‐tuned by appropriate selection of the monomers and their feed ratios. The presence of propargyl functional groups in the (co)polymers was confirmed by the presence of a thermal degradation step in the range from 450 °C to 455 °C. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3888–3900

Structural, DFT and biological studies on Cr(III) complexes of semi and thiosemicarbazide ligands derived from diketo hydrazide

Three ligands have been prepared by addition ethanolic suspension of 2-hydrazino-2-oxo-N-phenyl-acetamide to phenyl isocyanate (H2PAPS), phenyl isothiocyanate (H2PAPT) and benzoyl isothiocyanate (H2PABT). The Cr(III) chloride complexes were prepared and characterized by conventional techniques. The data confirmed that the complexes have the following formulaes, [Cr(H2PAPS)Cl3], [Cr(HPAPT)Cl2(H2O)2] and [Cr(HPABT)Cl2(H2O)]. The IR spectra of complexes shows that H2PAPS behaves as neutral tridentate via both CO of hydrazide moiety and CN(azomethine) due to enolization of CO isocyanate without deprotonation. H2PAPT suggests the coordination as mononegative bidentate via both CO of hydrazide moiety in keto and deprotonated enolic oxygen atoms. H2PABT act as mononegative tridentate via carbonyl oxygen (CO)3, the deprotonated enolic oxygen atom (CO)1 and NH1 groups. The experimental IR data of ligands are compared with those obtained theoretically from DFT calculations. Also, the bond lengths, bond angles, HOMO, LUMO and dipole moments have been calculated. The calculated HOMO-LUMO energy gap reveals that charge transfer occurs within the ligand molecules. The calculated values of binding energies indicates the higher stability of metal complexes than of ligands. Also, the kinetic and thermodynamic parameters for the different thermal degradation steps of the complexes were determined by Coats-Redfern and Horowitz-Metzger methods.

Surface modification of cellulose nanofibrils by maleated styrene block copolymer and their composite reinforcement application

Cellulose nanofibrils (CNFs) have been of great interest as reinforcing fillers because of their low density, high aspect ratio, and excellent mechanical strength properties. The advantages of CNFs, however, are often limited by their self-aggregation tendency and poor interfacial compatibility with hydrophobic polymer matrices. In this study, maleated styrene block copolymers were grafted on the surface of CNFs through esterification. The grafted polymer fraction of 25 wt% by gravimetric measurement was obtained. The evidence of grafting was also supported by changes in chemical functional groups and addition of the polymer thermal degradation step. A contact angle as high as 130° was observed on modified CNF film. The influences of modified CNFs on the surface morphology, thermal stability, and crystallinity were also evaluated and compared with those of neat CNFs. The reinforcing capability of CNFs as reinforcing fillers in the hydrophobic polymer matrix was assessed. The results also highlight the effect of improved compatibility between the surface modified CNF and polystyrene matrix to maintain optimum tensile strength at various filler concentrations.

On the Influence of the Sample Absorptivity when Studying the Thermal Degradation of Materials.

The change in absorptivity during the degradation process of materials is discussed, and its influence as one of the involved parameters in the degradation models is studied. Three materials with very different behaviors are used for the demonstration of its role: a carbon composite material, which is opaque, almost grey, a plywood slab, which is opaque and spectral-dependent and a clear PMMA slab, which is semitransparent. Data are analyzed for virgin and degraded materials at different steps of thermal degradation. It is seen that absorptivity and emissivity often reach high values in the range of 0.90–0.95 with a near-grey behavior after significant thermal aggression, but depending on the materials of interest, some significant evolution may be first observed, especially during the early stages of the degradation. Supplementary inaccuracy can come from the heterogeneity of the incident flux on the slab. As a whole, discrepancies up to 20% can be observed on the absorbed flux depending on the degradation time, mainly because of the spectral variations of the absorption and up to 10% more, depending on the position on the slab. Simple models with a constant and unique value of absorptivity may then lead to inaccuracies in the evaluation of the radiative flux absorption, with possible consequences on the pyrolysis analysis, especially for properties related to the early step of the degradation process, like the time to ignition, for example.

Novel water-soluble chitosan derivative prepared by graft polymerization of dicyandiamide: synthesis, characterisation, and its antibacterial property

Novel water soluble chitosan derivative of dicyandiamide chitosan (DCDA-g-CS) was synthesized by grafting polymerization of dicyandiamide DCDA onto chitosan CS. The presence of a new absorption peak in the infrared region of nitrile at 2297 cm−1 and NH at 1635 cm−1 of DCDA-g-CS and the chemical shift of 13C NMR at 120 and 162 ppm due to the presence of nitrile and carbon in DCDA clearly shows that the grafting process has taken place. The strong signal in the 1H NMR at 2.5 ppm could be assigned to the four protons in the amino group of DCDA, further confirms the formation of DCDA-g-CS. The polymer has shown to undergoing three steps of thermal degradation. The first stage was between 30 and 157 °C, followed by degradation step up to 350 °C and continuously degraded up to the high temperature set at 850 °C. The rate of degradation in the second stage which is slightly faster was considered as the rate determining step. The value of Tg was increased to 92.75 °C in DCDA-g-CS due to the considerable amount of DCDA was grafted onto the CS. The DCDA-g-CS was more soluble in water due to the decrease in crystallinity of chitosan after grafting as shown from X-ray diffraction spectra. The DCDA-g-CS shows high antibacterial activity at pH 7.0 and pH 4.0 the minimum inhibitory concentration (MIC) of gram-negative bacteria E. coli ATCC25922, the MIC at pH 7 and pH 4.0 were 62.5 and 125 μg/mL respectively and gram-positive bacteria S. aureus ATCC 29213, the MIC at pH 7 and pH 4 were 62.5 and 125 μg/mL respectively.

The investigation of thermal decomposition pathway and products of poly(vinyl alcohol) by TG‐FTIR

ABSTRACTA generalized form of a semiquantitative method has been developed based on the multilinear least‐squares regression technique applied on the entire FTIR absorbance spectrum of a gaseous mixture to determine components concentration. Thermal degradation of poly(vinyl alcohol) samples with high, PVA(98), and low degree of hydrolysis, PVA(80), has been investigated by TG‐FTIR simultaneous analysis performed in an inert atmosphere. Analysis of gaseous products was carried out using a routine developed in Matlab and this routine returns the product concentration with a reasonable RMS error. The correlation coefficients of the original mixture spectrum with the mixed output were obtained at some specific peak temperatures using irAnalysis software. The first process is the loss of physically adsorbed water which followed by two main processes of thermal degradation. In spite of the similarity of evolved gaseous products, two samples showed some differences in components concentrations identified in the volatile mixture. Acetaldehyde has been identified as the main volatile product in the first thermal degradation step of PVA(98) and PVA(80). The second major degradation product of PVA(80) is acetic acid due to presence of more residual acetate group while 2‐butenal have been identified for PVA(98). Water was mainly produced in the first stage of thermal degradation of PVA(98) while it was identified in the first and second stages for PVA(80). This might be attributed to existence of a competition between water and residual acetate group for elimination that postpones the complete elimination of OH group to the second degradation stage. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42117.