scholarly journals Prediction of Residual Curing Capacity of Melamine-Formaldehyde Resins at an Early Stage of Synthesis by In-Line FTIR Spectroscopy

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2541
Author(s):  
Regina Seidl ◽  
Stephanie Weiss ◽  
Rudolf W. Kessler ◽  
Waltraud Kessler ◽  
Edith M. Zikulnig-Rusch ◽  
...  
Keyword(s):  
Chemical Structure ◽  
Early Stage ◽  
Least Squares Regression ◽  
Melamine Formaldehyde ◽  
Scanning Calorimetry ◽  
Reaction Conditions ◽  
Surface Finishes ◽  
Initial Stage ◽  
Batch Modelling ◽  
Modelling Approach

Melamine-formaldehyde (MF) resins are widely used as surface finishes for engineered wood-based panels in decorative laminates. Since no additional glue is applied in lamination, the overall residual curing capacity of MF resins is of great technological importance. Residual curing capacity is measured by differential scanning calorimetry (DSC) as the exothermic curing enthalpy is integral to the liquid resin. After resin synthesis is completed, the resulting pre-polymer has a defined chemical structure with a corresponding residual curing capacity. Predicting the residual curing capacity of a resin batch already at an early stage during synthesis would enable corrective measures to be taken by making adjustments in the reaction conditions. Thereby, discarding faulty batches could be avoided. Here, by using a batch modelling approach, it is demonstrated how quantitative predictions of MF residual curing capacity can be derived from inline Fourier Transform infrared (FTIR) spectra recorded during resin synthesis using partial least squares regression. Not only is there a strong correlation (R2 = 0.89) between the infrared spectra measured at the end of MF resin synthesis and the residual curing capacity, but also the inline reaction spectra obtained already at the point of complete dissolution of melamine upon methylolation during the initial stage of resin synthesis are also well suited for predicting final curing performance of the resin and a valid regression model (R2 = 0.85) can be established using information obtained at a very early stage of MF resin synthesis.

Fabrication of Thermochromatic Microencapsulated Phase Change Materials

2011 ◽  
Vol 332-334 ◽  
pp. 1856-1859
Author(s):  
Xiao Hua Liao ◽  
Hai Feng Shi ◽  
Nan Song ◽  
Xing Xiang Zhang
Keyword(s):  
Molecular Structure ◽  
Differential Scanning Calorimetry ◽  
Chemical Structure ◽  
Phase Change Materials ◽  
In Situ Polymerization ◽  
Melamine Formaldehyde ◽  
Scanning Calorimetry ◽  
Microencapsulated Phase Change Materials ◽  
Structure Properties

Microencapsulated n-octadecane (MicroC18) and doped with thermochromatic powders (TC-MicroC18) were prepared with melamine-formaldehyde (M-F) resin as the wall via in-situ polymerization. The chemical structure and thermal behavior of microcapsules were investigated using fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). Experimental results show that 63 wt% n-C18 has been incorporated into microcapsules, and the obvious thermochromatic effect of TC-MicroC18 is displayed with temperature changing. The structure-properties of TC-MicroC18 also is discussed in detail from the aspect of molecular structure.

Anisotropy of interfacial defects in the initial stage of MOVPE GaAs growth On Si

1990 ◽  
Vol 48 (4) ◽  
pp. 592-593
Author(s):  
C. Vannuffel ◽  
C. Schiller ◽  
J. P. Chevalier
Keyword(s):  
Early Stage ◽  
Threading Dislocations ◽  
Mbe Growth ◽  
Detailed Mechanism ◽  
Si Substrates ◽  
Initial Stage ◽  
Interfacial Defects ◽  
Interfacial Dislocations ◽  
Step Growth ◽  
Essential Problem

Recently, interest has focused on the epitaxy of GaAs on Si as a promising material for electronic applications, potentially for integration of optoelectronic devices on silicon wafers. The essential problem concerns the 4% misfit between the two materials, and this must be accommodated by a network of interfacial dislocations with the lowest number of threading dislocations. It is thus important to understand the detailed mechanism of the formation of this network, in order to eventually reduce the dislocation density at the top of the layers.MOVPE growth is carried out on slightly misoriented, (3.5°) from (001) towards , Si substrates. Here we report on the effect of this misorientation on the interfacial defects, at a very early stage of growth. Only the first stage, of the well-known two step growth process, is thus considered. Previously, we showed that full substrate coverage occured for GaAs thicknesses of 5 nm in contrast to MBE growth, where substantially greater thicknesses are required.

Synthesis and properties of phthalonitrile-based resins containing spirocycle acetal

2020 ◽  
pp. 095400832097759
Author(s):  
Ke Li ◽  
Hua Yin ◽  
Kun Yang ◽  
Pei Dai ◽  
Ling Han ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Chemical Structure ◽  
Room Temperature ◽  
Laser Desorption Ionization ◽  
Scanning Calorimetry ◽  
Rheological Analysis ◽  
Ionization Time ◽  
Dynamic Mechanical ◽  
Nmr Spectrometry ◽  
Current Context

Designing novel low-melting, high-rigidity phthalonitrile resin is of great significance in the current context of development. In this study, rigid spirocycle acetal structure was introduced into phthalonitrile to reduce the melting point and maintain their thermal stability. The chemical structure of resins was confirmed by nuclear magnetic resonance (NMR) spectrometry, matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry and Fourier-transform infrared (FTIR) spectroscopy. The curing behaviors were studied by differential scanning calorimetry (DSC). Thermal stability and mechanical properties of the cured resins were investigated by dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). The processability was studied by rheological analysis. The results indicated the three monomers had a low melting temperature, wide processing windows and low viscosities. These polymers did not exhibit Tg from room temperature to 400°C, exhibited superb dynamic mechanical property and thermal stability.

scholarly journals Glossary and tutorial of xenobiotic metabolism terms used during small molecule drug discovery and development (IUPAC Technical Report)

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Paul Erhardt ◽  
Kenneth Bachmann ◽  
Donald Birkett ◽  
Michael Boberg ◽  
Nicholas Bodor ◽  
...  
Keyword(s):  
Drug Discovery ◽  
Small Molecule ◽  
Chemical Structure ◽  
Early Stage ◽  
Xenobiotic Metabolism ◽  
Drug Discovery And Development ◽  
Small Molecule Drug ◽  
Technical Report ◽  
Wide Range ◽  
Draft Version

Abstract This project originated more than 15 years ago with the intent to produce a glossary of drug metabolism terms having definitions especially applicable for use by practicing medicinal chemists. A first-draft version underwent extensive beta-testing that, fortuitously, engaged international audiences in a wide range of disciplines involved in drug discovery and development. It became clear that the inclusion of information to enhance discussions among this mix of participants would be even more valuable. The present version retains a chemical structure theme while expanding tutorial comments that aim to bridge the various perspectives that may arise during interdisciplinary communications about a given term. This glossary is intended to be educational for early stage researchers, as well as useful for investigators at various levels who participate on today’s highly multidisciplinary, collaborative small molecule drug discovery teams.

1H-NMR Analysis of Degree of Substitution in N,O-Carboxymethyl Chitosans from Various Chitosan Sources and Types

2012 ◽  
Vol 506 ◽  
pp. 158-161 ◽  
Author(s):  
A. Jaidee ◽  
Pornchai Rachtanapun ◽  
S. Luangkamin
Keyword(s):  
Chemical Structure ◽  
Carboxymethyl Chitosan ◽  
Degree Of Substitution ◽  
Resonance Spectroscopy ◽  
Nmr Analysis ◽  
Reaction Conditions ◽  
H Nmr ◽  
Fourier Transformed Infrared Spectroscopy ◽  
Chitosan Oligomer ◽  
Ft Ir

N,O-Carboxymethyl chitosans were synthesized by the reaction between shrimp, crab and squid chitosans with monochloroacetic acid under basic conditions at 50°C. The mole ratio of reactants was obtained from various reaction conditions of shrimp chitosan polymer and oligomer types. The mole ratio 1:12:6 of chitosan:sodium hydroxide:monochloroacetic acid was used for preparing carboxymethyl of chitosan polymer types while carboxymethyl of chitosan oligomer types were used the mole ratio 1:6:3 of chitosan:sodium hydroxide:monochloroacetic acid. The chemical structure was analyzed by fourier transformed infrared spectroscopy (FT-IR) and proton nuclear magnatic resonance spectroscopy (1H-NMR). The FT-IR was used for confirm the insertion of carboxymethyl group on chitosan molecules. The 1H-NMR was used for determining the degree of substitution (DS) of carboxymethylation at hydroxyl and amino sites of chitosans. Carboxymethyl chitosan samples had the total DS of carboxymethylation ranging from 1.0-2.2. The highest of DS of carboxymethylation was from shrimp chitosan oligomer type.

INTERACTION BETWEEN A FAMILY DOCTOR AND A DENTIST AT AN EARLY STAGE IN THE PREVENTION OF DISEASES OF THE GASTROINTESTINAL TRACT

2021 ◽  
Vol 2 (12(81)) ◽  
pp. 39-43
Author(s):  
M. Ibragimov ◽  
Y. Heydarova ◽  
A. Alizade ◽  
L. Ibragimova
Keyword(s):  
Gastrointestinal Tract ◽  
Oral Cavity ◽  
Early Stage ◽  
Family Doctor ◽  
Scientific Article ◽  
Oral Manifestations ◽  
Family Doctors ◽  
Long Period ◽  
Initial Stage ◽  
The Relationship

This scientific article discusses the oral manifestations of diseases of the gastrointestinal tract. This problem is relevant both for dentists and family doctors. In medicine, for a long period of time, the relationship between diseases affecting the gastrointestinal tract and their symptoms manifested in the oral cavity has been considered. Many scientists and physicians have dealt with this problem, their several opinions are presented in this article. There is a hypothesis among researchers that the oral cavity is a mirror in which all human diseases can be visible. In the oral cavity, most of the alterations occurring in the organism are manifested, due to which, with an attentive attitude to oral manifestations, the disease can be detected already at the initial stage.

Thermotropic behavior of sodium cholesteryl carbonate

2009 ◽  
Vol 24 (1) ◽  
pp. 156-163 ◽  
Author(s):  
Rabkwan Chuealee ◽  
Timothy S. Wiedmann ◽  
Teerapol Srichana
Keyword(s):  
Phase Behavior ◽  
Chemical Structure ◽  
Liquid Crystalline ◽  
Polarized Light ◽  
Wave Number ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
X Ray Scattering ◽  
C Nmr

Sodium cholesteryl carbonate ester (SCC) was synthesized, and its phase behavior was studied. The chemical structure was assessed by solid-state infrared spectroscopy based on vibration analysis. The wave number at 1705 and 1276 cm−1 corresponds to a carbonyl carbonate and O–C–O stretching of SCC, respectively. Molecular structure of SCC was further investigated with 1H and 13C NMR spectroscopy. The chemical shift, for the carbonyl carbonate resonance appeared at 155.5 ppm. A molecular mass of SCC was at m/z of 452. Differential scanning calorimetry (DSC), video-enhanced microscopy (VEM) together with polarized light microscopy, and small-angle x-ray scattering (SAXS) were used to characterize the phase behavior as a function of temperature of SCC. Liquid crystalline phase was formed with SCC. Based on the thermal properties and x-ray diffraction, it appears that SCC forms a structure analogous to the type II monolayer structure observed with cholesterol esters.

scholarly journals Brazilian gutta-percha points. Part II: thermal properties

2007 ◽  
Vol 21 (1) ◽  
pp. 29-34 ◽  
Author(s):  
Cláudio Maniglia-Ferreira ◽  
Eduardo Diogo Gurgel-Filho ◽  
João Batista Araújo Silva Jr ◽  
Regina Célia Monteiro de Paula ◽  
Judith Pessoa Andrade Feitosa ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Thermal Properties ◽  
Physical Properties ◽  
Ambient Temperature ◽  
Amorphous Phase ◽  
Thermal Behaviour ◽  
Chemical Structure ◽  
Scanning Calorimetry ◽  
Gutta Percha ◽  
Thermal Manipulation

This study was undertaken to explore the effect of heating on gutta-percha, analyzing the occurrence of endothermic peaks corresponding to the transformation that occurs in the crystalline structure of the polymer during thermal manipulation. This study also seeked to determine the temperature at which these peaks occur, causing a transformation from the beta- to the alpha-form, and from the alpha- to the amorphous phase. Eight nonstandardized gutta-percha points commercially available in Brazil (Konne, Tanari, Endopoint, Odous, Dentsply 0.04, Dentsply 0.06, Dentsply TP, Dentsply FM) and pure gutta-percha (control) were analysed using differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). The transition temperatures were determined and analysed. With the exception of Dentsply 0.04 and Dentsply 0.06, the majority of the products showed thermal behaviour typical of beta-gutta-percha, with two endothermic peaks, exhibiting two crystalline transformations upon heating from ambient temperature to 130°. Upon cooling and reheating, few samples presented two endothermic peaks. It was concluded that heating dental gutta-percha to 130°C causes changes to its chemical structure which permanently alter its physical properties.

scholarly journals Morphofunctional characteristics of endothelial cells in coronary atherosclerosis

2011 ◽  
Vol 63 (4) ◽  
pp. 921-932 ◽  
Author(s):  
Vesna Lackovic ◽  
Irena Tanaskovic ◽  
Dj. Radak ◽  
Vesna Nesic ◽  
Z. Gluvic ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Coronary Atherosclerosis ◽  
Complex Disease ◽  
Early Stage ◽  
Intercellular Junctions ◽  
Vascular Wall ◽  
Functional Changes ◽  
Initial Stage ◽  
Numerous Data

Atherosclerosis represents a complex disease which encompasses all the components of the vascular wall. Nevertheless, according to all known theories of the pathogenesis of atherosclerosis, the key role in this process belongs to the endothelial cells, i.e. the changes that they are subjected to especially during the initial stage of the lesion. In this review we have attempted, according to the results of our continuous research and numerous data from available modern literature, to show the cytohistological characteristics of endothelial cells, as well as the changes they are subjected to in all stages of atherosclerosis. In the first part we have reviewed the ultrastructure, function and pathology of the endothelium, subcellular organization of the endothelial cells, their specific characteristics, micro compartments and intercellular junctions. In the second part we have described the morphological and functional changes of endothelial cells during atherosclerosis. Special attention is given to the role of endothelial cells in the development of the initial stage of lesion: endothelial dysfunction, factors that cause the increased expression of adhesion molecules in endothelial cells and mechanisms that cause leukocytes to migrate through the endothelial layer to subendothelial connective tissue in the early stage of atherosclerosis.

Systematic Characterization of Different Quaternary Ammonium Salts to be Used in Organoclays

2012 ◽  
Vol 727-728 ◽  
pp. 1552-1556
Author(s):  
Renata Barbosa ◽  
Dayanne Diniz Souza ◽  
Edcleide Maria Araújo ◽  
Tomás Jefférson Alves de Mélo
Keyword(s):  
Thermal Stability ◽  
Quaternary Ammonium ◽  
Chemical Structure ◽  
Quaternary Ammonium Salts ◽  
Ammonium Salts ◽  
Degradation Mechanisms ◽  
Scanning Calorimetry ◽  
Higher Temperature ◽  
Thermal Stability Of

Studies of degradation have verified that the decomposition of some quaternary ammonium salts can begin to be significant at the temperature of about 180 ° C and like most thermoplastics are processed at least around this temperature, the thermal stability of the salt in clay should always be considered. Some salts are more stable than others, being necessary to study the degradation mechanisms of each case. In this work, four quaternary ammonium salts were characterized by differential scanning calorimetry (DSC) and thermogravimetry (TG). The results of DSC and TG showed that the salts based chloride (Cl-) anion begin to degrade at similar temperatures, while the salt based bromide (Br-) anion degrades at higher temperature. Subsequently, a quaternary ammonium salt was chosen to be used in organoclays, depending on its chemical structure and its thermal behavior.

Sign in / Sign up

Export Citation Format

Share Document