Study of the Infrared Spectral Features of an Epoxy Curing Mechanism

2008 ◽  
Vol 62 (10) ◽  
pp. 1129-1136 ◽  
Author(s):  
Liang Li ◽  
Qili Wu ◽  
Shanjun Li ◽  
Peiyi Wu
Keyword(s):  
Correlation Analysis ◽  
Near Infrared ◽  
Nir Spectroscopy ◽  
Diglycidyl Ether ◽  
Hydroxyl Groups ◽  
Spectral Correlation ◽  
Derivative Analysis ◽  
Curing Mechanism ◽  
Infrared Spectral ◽  
Epoxy Groups

In this work, the isothermal curing process of diglycidyl ether of bisphenol A(DGEBA) cured with 4,4′-diaminodiphenylmethane (DDM) was monitored in situ by mid-infrared (MIR) and near-infrared (NIR) spectroscopy. With the help of generalized two-dimensional (2D) correlation analysis, the results obtained showed that, during curing, the change of amine and epoxy groups was simultaneous, taking place prior to the change of hydroxyl groups, followed by the change of CH2/CH groups, resulting from the ring-opening reaction of epoxy groups. In addition, 2D MIR×NIR hetero-spectral correlation analysis and second-derivative analysis were also employed, by means of which direct evidence of the curing mechanism could be obtained and obscure NIR band assignments in the overlapped CH combination region could be made.

scholarly journals Some Applications of Vibrational Spectroscopy for the Analysis of Polymers and Polymer Composites

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1159 ◽  
Author(s):  
Liliane Bokobza
Keyword(s):  
Polymer Composites ◽  
Vibrational Spectroscopy ◽  
Near Infrared ◽  
Nir Spectroscopy ◽  
Polymeric Materials ◽  
Molecular Structures ◽  
Hydroxyl Groups ◽  
Inorganic Particles ◽  
Reinforcing Fillers

Vibrational spectroscopies, including infrared and Raman techniques, are important tools for the characterization of chemical composition, molecular structures, and chain orientation under mechanical deformation of polymeric materials. The development of fiber-optic-based spectrometers has broadened the use of vibrational spectroscopy for process monitoring in various fields including polymerization, curing, and manufacturing processes. Combined with chemometrics, near-infrared (NIR) spectroscopy is now recognized as one of the most important techniques for polymer analyses. Infrared and Raman studies also offer invaluable means for the analysis of inorganic particles used as reinforcing fillers for polymers. The characterization of surface species and the nature of interfacial bonding between the organic and inorganic phases are important issues for the understanding of composite properties. Infrared spectroscopy is particularly convenient for the detection and analysis of hydroxyl groups on filler surfaces, and Raman spectroscopy is particularly well suited for the study of carbon-based materials. In both techniques, polymer-filler interactions can be evidenced through frequency shifts or width changes of bands associated with vibrational modes of functional groups of either macromolecular chains or filler particles. Selected examples of application of infrared and Raman spectroscopies illustrate their potential for monitoring polymer processes, measuring polymer orientation, and characterizing polymer composites.

Quantitative Analysis of Hydrogen Bonding in Poly(4-Vinylphenol) Blends Using near Infrared Spectroscopy

2003 ◽  
Vol 11 (3) ◽  
pp. 183-191 ◽  
Author(s):  
Haijun Cai ◽  
Josée Brisson
Keyword(s):  
Hydrogen Bonding ◽  
Near Infrared ◽  
Nir Spectroscopy ◽  
Weight Fraction ◽  
Hydroxyl Groups ◽  
Absorption Coefficients ◽  
Oh Groups ◽  
Refinement Method ◽  
Poly Ethylene ◽  
Vinyl Phenol

Quantitative evaluation of hydrogen bonding of poly(4-vinyl phenol)/poly(ethylene oxide) PVPh/PEO blends was conducted using Fourier transform near infrared (FT-NIR) spectroscopy. Absorption coefficients of the free ( aF), intra- (PVPh–PVPh) ( aA) and inter-associated (PVPh–PEO) hydroxyl groups ( aI) were estimated. Two sets of approximations were tested, including adopting a least-squares refinement method to calculate absorption coefficients from all NIR spectra or using a literature value for aF. Each set of absorption coefficients thus estimated were used to determine hydroxyl concentration for the free and hydrogen-bonded hydroxyl overtone bands in the blends. A comparison is made among the resultant concentrations of the free, intra- and inter-associated hydroxyl groups. The concentration of free hydroxyl groups markedly decreases with PEO percentage, and that of intra-associated hydroxyl remains almost constant. Concentration for the inter-associated hydroxyl groups in the blends increases very slowly above 0.2 PEO weight fraction. When concentration of OH groups is reported per PVPh chain, FT-NIR measurements show a broad maximum in the number of interchain hydrogen bonds. This result can be used to explain partially previous orientation behaviour observed for PVPh/PEO blends.

Near Infrared Technology in Hungary and the Influence of Karl H. Norris on Our Success

1996 ◽  
Vol 4 (1) ◽  
pp. 63-67
Author(s):  
Karoly J. Kaffka
Keyword(s):  
Near Infrared ◽  
New Technology ◽  
Collaborative Work ◽  
Nir Spectroscopy ◽  
Cooperation Agreement ◽  
Food Research ◽  
Food And Agriculture ◽  
Infrared Spectral ◽  
History Of ◽  
Central Food

The history of Hungarian activity in the field of near infrared spectroscopy is summarised in this paper, beginning in 1972 when Karoly Vas, Director of the Hungarian Central Food Research Institute, visited the Instrumentation Research Laboratory of the USDA Agriculutural Research Center in Beltsville, Maryland, and met Karl H. Norris. There, Karoly Vas became acquainted with the new technology using the near infrared spectral region for multi-component analysis and recognised its importance and perspectives. Through a cooperation agreement between the USDA and the Hungarian Ministry of Food and Agriculture, a close collaboration was established between the two institutes. Many Hungarian researchers—the author, L. Horváth, B.T. Nádai, J.L. Gönczy, A. Czabaffy, F. Kulcsár, M. Váradi and G. Kiskó—involved in NIR technology have had the opportunity to spend some time in Beltsville and to enjoy Karl H. Norris' deep knowledge of NIR spectroscopy, his unbelievable skill in this field of science, accompanied with the willingness to share his experiences and results. The results of the collaborative work achieved in the analysis of wine, sunflower seed, pastry products, cocoa powder, dietary fibre etc., using NIR technology are presented here. Karl H. Norris' valuable contribution is emphasised.

scholarly journals Fraud Detection in Batches of Sweet Almonds by Portable Near-Infrared Spectral Devices

Foods ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1221
Author(s):  
Irina Torres ◽  
María-Teresa Sánchez ◽  
Miguel Vega-Castellote ◽  
Dolores Pérez-Marín
Keyword(s):  
Near Infrared ◽  
Nir Spectroscopy ◽  
Accurate Method ◽  
Training Set ◽  
Production Chain ◽  
Future Studies ◽  
Infrared Spectral ◽  
Portable Instruments ◽  
New Generation ◽  
Sweet Almond

One of the key challenges for the almond industry is how to detect the presence of bitter almonds in commercial batches of sweet almonds. The main aim of this research is to assess the potential of near-infrared spectroscopy (NIRS) by means of using portable instruments in the industry to detect batches of sweet almonds which have been adulterated with bitter almonds. To achieve this, sweet almonds and non-sweet almonds (bitter almonds and mixtures of sweet almonds with different percentages (from 5% to 20%) of bitter almonds) were analysed using a new generation of portable spectrophotometers. Three strategies (only bitter almonds, bitter almonds and mixtures, and only mixtures) were used to optimise the construction of the non-sweet almond training set. Models developed using partial least squares-discriminant analysis (PLS-DA) correctly classified 86–100% of samples, depending on the instrument used and the strategy followed for constructing the non-sweet almond training set. These results confirm that NIR spectroscopy provides a reliable, accurate method for detecting the presence of bitter almonds in batches of sweet almonds, with up to 5% adulteration levels (lower levels should be tested in future studies), and that this technology can be readily used at the main steps of the production chain.

scholarly journals Characterization of Articular Cartilage Recovery and Its Correlation with Optical Response in the Near-Infrared Spectral Range

Cartilage ◽  
2016 ◽  
Vol 8 (3) ◽  
pp. 307-316 ◽  
Author(s):  
Isaac Oluwaseun Afara ◽  
Sanjleena Singh ◽  
Hayley Moody ◽  
Lihai Zhang ◽  
Adekunle Oloyede
Keyword(s):  
Articular Cartilage ◽  
Near Infrared ◽  
Elastic Recovery ◽  
Arthroscopic Surgery ◽  
Nir Spectroscopy ◽  
Optical Response ◽  
Enzymatic Treatment ◽  
Least Squares Regression ◽  
Infrared Spectral ◽  
Recovery Response

Objectives: In this study, we examine the capacity of a new parameter, based on the recovery response of articular cartilage, to distinguish between healthy and damaged tissues. We also investigate whether or not this new parameter correlates with the near-infrared (NIR) optical response of articular cartilage. Design: Normal and artificially degenerated (proteoglycan-depleted) bovine cartilage samples were nondestructively probed using NIR spectroscopy. Subsequently they were subjected to a load and unloading protocol, and the recovery response was logged during unloading. The recovery parameter, elastic rebound ( ER), is based on the strain energy released as the samples underwent instantaneous elastic recovery. Results: Our results reveal positive relationship between the rebound parameter and cartilage proteoglycan content (normal samples: 2.20 ± 0.10 N mm; proteoglycan-depleted samples: 0.50 ± 0.04 N mm for 1 hour of enzymatic treatment and 0.13 ± 0.02 N mm for 4 hours of enzymatic treatment). In addition, multivariate analysis using partial least squares regression was employed to investigate the relationship between ER and NIR spectral data. The results reveal significantly high correlation ( R2cal = 98.35% and R2val = 79.87%; P < 0.0001), with relatively low error (14%), between the recovery and optical response of cartilage in the combined NIR regions 5,450 to 6,100 cm−1 and 7,500 to 12,500 cm−1. Conclusion: We conclude that ER can indicate the mechanical condition and state of health of articular cartilage. The correlation of ER with cartilage optical response in the NIR range could facilitate real-time evaluation of the tissue’s integrity during arthroscopic surgery and could also provide an important tool for cartilage assessment in tissue engineering and regeneration research.

Two-Dimensional near Infrared Correlation Spectroscopy: Principle and its Applications

1998 ◽  
Vol 6 (1) ◽  
pp. 19-31 ◽  
Author(s):  
Yukihiro Ozaki ◽  
Yan Wang
Keyword(s):  
Correlation Analysis ◽  
Basic Principle ◽  
Near Infrared ◽  
Nir Spectroscopy ◽  
Correlation Spectroscopy ◽  
Mathematical Treatment ◽  
Two Dimensional ◽  
2D Correlation Spectroscopy

The basic principle and applications of generalised two-dimensional (2D) near infrared (NIR) correlation spectroscopy are reviewed in this paper. A brief history and the basic principle of 2D correlation spectroscopy are described first, and then its importance for NIR spectroscopy is discussed. An outline of the mathematical treatment of generalised 2D correlation spectroscopy is given. Several examples of generalised 2D NIR and 2D NIR-mid IR (MIR) heterospectral correlation analysis are introduced.

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