scholarly journals Synthesis and Characterization of Low-Cost Cresol-Based Benzoxazine Resins as Potential Binders in Abrasive Composites

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2995
Author(s):  
Artur Jamrozik ◽  
Mateusz Barczewski ◽  
Grzegorz Framski ◽  
Daniel Baranowski ◽  
Paulina Jakubowska ◽  
...  
Keyword(s):  
Low Cost ◽  
2D Nmr ◽  
Additional Analysis ◽  
Resonance Spectroscopy ◽  
Scanning Calorimetry ◽  
Voc Emission ◽  
Chemical Structures ◽  
Oxazine Ring ◽  
Nmr Techniques

A series of cresol-based benzoxazines were synthesized for potential application as a polymer matrix in abrasive composites. The chemical structures of the obtained benzoxazine resins were investigated in detail using Fourier transform infrared spectroscopy (FTIR) and hydrogen-1 as well as carbon-13 nuclear magnetic resonance spectroscopy (1H NMR, 13C NMR) with an additional analysis using two-dimensional NMR techniques (2D NMR 1H-1H COSY, 1H-13C gHSQC and gHMBC). Structural analysis confirmed the presence of vibrations of -O-C-N- at ~950 cm−1 wavenumber, characteristic for an oxazine ring. The thermal properties of benzoxazine monomers were examined using differential scanning calorimetry (DSC) analysis. The polymerization enthalpy varied from 143.2 J/g to 287.8 J/g. Thermal stability of cresol-based benzoxazines was determined using thermogravimetry (TGA) analysis with additional analysis of the amount of volatile organic compounds (VOC) emitted from the synthesized benzoxazines during their crosslinking by static headspace coupled with gas chromatography technique (HS-GC). The amount of residual mass significantly differed between all synthesized polybenzoxazines in the range from 8.4% to 21.2%. The total VOC emission for benzoxazines decreased by 46–77% in reference to a conventional phenolic binder. The efficiency of abrasive composites with the benzoxazine matrix was evaluated based on abrasion tests. Performed analyses confirmed successful synthesis and proper chemical structure of cresol-based benzoxazines. All the experiments indicated that benzoxazines based on different cresol isomers significantly differ from each other. Good thermal performance and stability of the abrasive composites with the polybenzoxazine matrix and significantly lower VOC emission allow us to state that benzoxazines can be a promising and valuable alternative to the phenolics and a new path for the development of modern, eco-friendly abrasives.

scholarly journals CHARACTERISATION OF INCLUSION COMPLEXES BETWEEN BIFONAZOLE AND DIFFERENT CYCLODEXTRINS IN SOLID AND SOLUTION STATE

2017 ◽  
Vol 36 (1) ◽  
pp. 81 ◽  
Author(s):  
Hajnal Kelemen ◽  
Angella Csillag ◽  
Gabriel Hancu ◽  
Blanka Székely-Szentmiklósi ◽  
Ibolya Fülöp ◽  
...  
Keyword(s):  
Inclusion Complexes ◽  
Binary Systems ◽  
Pharmaceutical Formulations ◽  
2D Nmr ◽  
Local Drug Delivery ◽  
Stable Complex ◽  
Resonance Spectroscopy ◽  
Scanning Calorimetry ◽  
2D Nmr Spectroscopy ◽  
Major Drawback

The aim of this study is to confirm the formation of inclusion complexes between bifonazole (BFZ) and different cyclodextrin (CD) derivatives. Bifonazole, an imidazole antifungal derivative,is a very hydrophobic compound, which is a major drawback in obtaining topical pharmaceutical formulations with optimal bioavailability. Cyclodextrins may increase local drug delivery by enhancing the drug release and/or permeation. The binary systems between bifonazole and cyclodextrins were prepared in two molar ratios by physical-mixture methods.The physicochemical properties of these complexes were studied by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR) methods. Results showed favourable molecular interaction between the components, in solid state and in solution. 1H NMR -CD titrations and molecular modelling study showed that the most stable complex was obtained when using γ-CD. The Job’s method and 2D NMR spectroscopy sustain the 2:1 stoichiometry of the BFZ:γ-CD complex.

Preparation and properties of shape-stabilized phase change material cellulose benzoate-g-polyoxyethylene (2) hexadecyl ether with potential for thermal energy storage

2018 ◽  
Vol 89 (8) ◽  
pp. 1512-1521
Author(s):  
Na Han ◽  
Wenxin Zhang ◽  
Xiufang Wang ◽  
Xingxiang Zhang ◽  
Wei Li ◽  
...  
Keyword(s):  
Phase Transition ◽  
Energy Storage ◽  
Phase Change ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Solid Phase ◽  
Resonance Spectroscopy ◽  
Thermal Reliability ◽  
Scanning Calorimetry ◽  
Chemical Structures

It is a worldwide challenge to efficiently use renewable resources to solve the current energy shortage. The existing cellulose-based material is incapable of proper power storage. In this study, a series of cellulose benzoate-g-polyoxyethylene (2) hexadecyl ether (CB-g-E2C16) solid–solid phase change materials were synthesized with cellulose as the skeleton and polyoxyethylene (2) hexadecyl ether (E2C16) as a functional side chain. The skeleton cellulose and benzoyl chloride restrict the free movement of the molecular chains of E2C16 above the phase transition temperature, leading to a solid–solid phase change. Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy were performed to investigate the chemical structures. The thermal energy-storage properties, thermal reliability and thermal stability of the CB-g-E2C16 were investigated by differential scanning calorimetry and thermogravimetry (TG) methods. The analysis results indicated that the E2C16 chains were successfully grafted onto the cellulose benzoate (CB) backbone and the copolymers exhibited typical solid–solid phase transition behavior. The enthalpy and degree of substitution of graft copolymers CB-g-E2C16 could be adjusted by changing the feeding ratio of the raw materials, reaction temperature and post-processing methods of CB. TG analysis results showed that the CB-g-E2C16 copolymers possessed good thermostability and they keep their stability up to 278℃. Compared with pure cellulose, CB-g-E2C16 copolymers could be dissolved in dimethyl sulfoxide and most of them could be dissolved in N, N-dimethylformamide.

scholarly journals Analysis of Bio-Based Fatty Esters PCM’s Thermal Properties and Investigation of Trends in Relation to Chemical Structures

2019 ◽  
Vol 9 (2) ◽  
pp. 225 ◽  
Author(s):  
Rebecca Ravotti ◽  
Oliver Fellmann ◽  
Nicolas Lardon ◽  
Ludger Fischer ◽  
Anastasia Stamatiou ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Phase Change ◽  
Energy Demand ◽  
Phase Change Materials ◽  
Arachidic Acid ◽  
Resonance Spectroscopy ◽  
Scanning Calorimetry ◽  
Fatty Esters ◽  
Latent Heat Storage ◽  
Chemical Structures

As global energy demand increases while primary sources and fossil fuels’ availability decrease, research has shifted its focus to thermal energy storage systems as alternative technologies able to cover for the mismatch between demand and supply. Among the different phase change materials available, esters possess particularly favorable properties with reported high enthalpies of fusion, low corrosivity, low toxicity, low supercooling, thermal and chemical stability as well as biodegradability and being derived from renewable feedstock. Despite such advantages, little to no data on the thermal behavior of esters is available due to low commercial availability. This study constitutes a continuation of previous works from the authors on the investigation of fatty esters as novel phase change materials. Here, methyl, pentyl and decyl esters of arachidic acid, and pentyl esters of myristic, palmitic, stearic and behenic acid are synthesized through Fischer esterification with high purities and their properties are studied. The chemical structures and purities are confirmed through Attenuated Total Reflectance Infrared Spectroscopy, Gas Chromatography coupled with Mass Spectroscopy and Nuclear Magnetic Resonance Spectroscopy, while the determination of the thermal properties is performed through Differential Scanning Calorimetry and Thermogravimetric Analysis. In conclusion, some correlations between the melting temperatures and the chemical structures are discovered, and the fatty esters are assessed based on their suitability as phase change materials for latent heat storage applications.

scholarly journals Design of High-Performance Polybenzoxazines with Tunable Extended Networks Based on Resveratrol and Allyl Functional Benzoxazine

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2794
Author(s):  
Yunliang Xing ◽  
Xianru He ◽  
Rui Yang ◽  
Kan Zhang ◽  
Shengfu Yang
Keyword(s):  
High Performance ◽  
Condensation Reaction ◽  
Good Thermal Stability ◽  
Chemical Structures ◽  
Dsc Measurements ◽  
Mannich Condensation ◽  
Polymerization Behavior ◽  
Oxazine Ring ◽  
Nmr Techniques ◽  
Ft Ir

A novel resveratrol-based bio-benzoxazine monomer (RES-al) containing an allyl group has been synthesized using resveratrol, allylamine, and paraformaldehyde via Mannich condensation reaction, and its chemical structures have been characterized by FT-IR spectroscopy and NMR techniques. The polymerization behavior of this benzoxazine resin has been investigated using in situ FT-IR and differential scanning calorimeter (DSC) measurements, and the thermal-mechanical properties of its corresponding polybenzoxazines are evaluated by DMA and TGA. We show that by controlling the curing process of the oxazine ring, the C=C bond in resveratrol, and the allyl group in RES-al, the cross-linking network of the polybenzoxazine can be manipulated, giving rise to tunable performance of thermosets. As all curable functionalities in RES-al are polymerized, the resulted polybenzoxazine exhibits a good thermal stability with a Tg temperature of 313 °C, a Td5 value of 352 °C, and char yield of 53% at 800 °C under N2.

scholarly journals Isolation and Characterization of Two New Antimicrobial Acids from Quercus incana (Bluejack Oak)

2018 ◽  
Vol 2018 ◽  
pp. 1-5
Author(s):  
Rizwana Sarwar ◽  
Umar Farooq ◽  
Sadia Naz ◽  
Nadia Riaz ◽  
Syed Majid Bukhari ◽  
...  
Keyword(s):  
Ethyl Acetate Fraction ◽  
Structural Formula ◽  
2D Nmr ◽  
Spectroscopic Technique ◽  
Pentanoic Acid ◽  
One Dimensional ◽  
Isolation And Characterization ◽  
Nmr Techniques ◽  
New Compounds

Two new compounds [1-2] were purified from ethyl acetate fraction of Quercus incana. The structure of these compounds is mainly established by using advanced spectroscopic technique such as UV, IR, one-dimensional (ID) and two-dimensional (2D) NMR techniques, and EI mass. The structural formula was deduced to be 4-hydroxydecanoic acid [1] and 4-hydroxy-3-(hydroxymethyl) pentanoic acid [2]. Both isolated compounds were tested for their antimicrobial potential and showed promising antifungal activity against Aspergillus niger and Aspergillus flavus.

scholarly journals Versatile1H−31P−31P COSY 2D NMR Techniques for the Characterization of Polyphosphorylated Small Molecules

2010 ◽  
Vol 75 (10) ◽  
pp. 3214-3223 ◽  
Author(s):  
Ananya Majumdar ◽  
Yan Sun ◽  
Meha Shah ◽  
Caren L. Freel Meyers
Keyword(s):  
Small Molecules ◽  
2D Nmr ◽  
Nmr Techniques

scholarly journals Synthesis and characterization of allyl- and vinyl-substituted 1,2-bis(tetrazolo)ethanes as polymeric precursors

2016 ◽  
Vol 71 (12) ◽  
pp. 1199-1209
Author(s):  
Vera A. Hartdegen ◽  
Maximilian S. Hofmayer ◽  
Konstantin Karaghiosoff ◽  
Thomas M. Klapötke
Keyword(s):  
Allyl Bromide ◽  
2D Nmr ◽  
Synthesis And Characterization ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
2D Nmr Spectroscopy ◽  
X Ray ◽  
Physical Stimuli ◽  
Thermal Stability Of

AbstractOn the basis of 1,2-bis(5-tetrazolo)ethane (BTE) the corresponding twofold vinyl and allyl N-substituted derivatives were synthesized using 1,2-dibromoethane and allyl bromide, respectively. The compounds were obtained as two different constitutional isomers. Both species were analyzed using NMR and IR spectroscopy, elemental analysis, as well as mass spectrometry. In the case of the diallyl bistetrazoles, the two isomers were characterized using 2D NMR spectroscopy. The synthesis of the divinyl compounds gave crystals of the 2,2′-N-substituted isomer, which were analyzed by single-crystal X-ray diffraction. The thermal stability of the compounds was determined using differential scanning calorimetry (DSC) and gave decomposition temperatures around 190°C and 230°C. For the investigation of the inherent energetic potential, sensitivities toward physical stimuli and detonation parameters were determined. The compounds turned out to be insensitive toward friction and impact and possess moderate energetic properties.

Characterization of non-cellulosic glucans in Eucalyptus globulus Labill. wood and kraft pulp

Holzforschung ◽  
2007 ◽  
Vol 61 (5) ◽  
pp. 478-482 ◽  
Author(s):  
Sara A. Lisboa ◽  
Dmitry V. Evtuguin ◽  
Carlos Pascoal Neto
Keyword(s):  
Eucalyptus Globulus ◽  
Fiber Surface ◽  
2D Nmr ◽  
Structural Features ◽  
Kraft Pulping ◽  
Hot Water ◽  
Pulp Yield ◽  
Naoh Solution ◽  
Nmr Techniques

Abstract The amount of non-cellulosic glucans in Eucalyptus globulus wood (approx. 4.5%) was assessed by extraction of sawdust with a 0.5 M NaOH solution at 90–120°C and the structural features were elucidated in a glucan-enriched polysaccharide fraction isolated by hot water extraction (120°C, 2 h). Isolated soluble glucans were characterized by wet chemistry methods and a set of 1D and 2D NMR techniques. The major proportion of glucans consisted of amylose (20%) and amylopectin (80%), although a small proportion of β-(1→3)-glucan (<0.2% on wood weight) was also detected. Although glucans are easily removed in the initial phase of kraft pulping, notable amounts were found in unbleached pulp and it was supposed that in the final stage of kraft pulping a fraction of α-glucan is precipitated onto the fiber surface and contributes to the pulp yield.

Characterization of partially deuteriated transition metal polyhydrido complexes by heteronuclear 2D NMR techniques

1991 ◽  
Vol 29 (13) ◽  
pp. S38-S44 ◽  
Author(s):  
Daniel Nanz ◽  
Wolfgang Von Philipsborn ◽  
Urs E. Bucher ◽  
Luigi M. Venanzi
Keyword(s):  
Transition Metal ◽  
2D Nmr ◽  
Nmr Techniques
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