Infrared Spectroscopy curing

Analysis of Cure. Infrared spectroscopy was utilized to examine film cure and the effect of stabilizers upon the cure of the epoxy acrylate. Pre-cured material has absorptions at 1635, 1410 and 810 cm-1 which clearly diminish after the resin is UV-irradiated (Figure 6). The 1635 cm-1 absorption can be assigned to the carbon-carbon stretch of an olefinic bond in conjugation with a carbonyl group the 1410 cm-1 can be assigned to the CH2 in-plane deformation of a vinylic group. The 810 cm-1 can also be assigned to some aspect of vinylic... 

Spectroscopy. Infrared spectroscopy (48) permits stmctural definition, eg, it resolves the 2,2 - from the 2,4 -methylene units in novolak resins. However, the broad bands and severely overlapping peaks present problems. For uncured resins, nmr rather than ir spectroscopy has become the technique of choice for microstmctural information. However, Fourier transform infrared (ftir) gives useful information on curing phenoHcs (49). Nevertheless, ir spectroscopy continues to be used as one of the detectors in the analysis of phenoHcs by gpc. 

No epoxy groups were detectable in the cured polymer by infrared spectroscopy. 

Polymerization Behavior. Both Fourier-transform infrared spectroscopy (FTIR) and differential scanning photocalorimetry (DPC) were used to characterize the polymerization behavior, curing time, and maximum double bond conversion in these systems. 

Bisphthalonitrile monomers were cured neat, with nucleophilic and redox co-reactants, or in combination with a reactive diluent. Dynamic mechanical measurements on the resulting polymers from -150 to +300°C turn up several differences attributable to differences in network structure. Rheovibron results were supplemented with solvent extraction, differential scanning calorimetry (DSC), vapor pressure osmometry, and infrared spectroscopy to characterize the state of cure. 

Figure 5. Monitoring of thermal cure by infrared spectroscopy.

Fourier transform Infrared spectroscopy has been shown to be an excellent tool for surface and Interface studies (.2), In this paper, the application of reflection/absorption Fourier transform Infrared spectroscopy (FTIR-RA) for studying the degradation of amine-cured epoxy and polybutadiene coatings on cold-rolled steel after exposure to a warm, humid environment is reported. 

In films cured initially at 175°C, determination by infrared spectroscopy of the concentration of anhydride groups indicated that all potential cross-linking groups had reacted. 

Polymerization Kinetics and Cure Studies [2,4,25] Infrared spectra of monomers differ markedly from spectra of the polymers [2], As a consequence, it is possible to use infrared spectroscopy to follow the course of polymerization reactions and to simultaneously analyze the structure of the polymer [2]. 

This article will review the impact of two powerful new techniques for characterizing epoxy resins at the molecular level — Fourier transform infrared spectroscopy (FT-IR) and high resolution nuclear magnetic resonance (NMR) of solids. Fortunately, these two techniques are not inhibited appreciably by the insoluble nature of the cured resin. Consequently, substantial structural information at the molecular level can be obtained. In this article, the basis of the methods will be briefly described in order to appreciate the nature of the methods followed by a description of the work on epoxies to date and finally some indication will be given of the anticipated contributions of these methods in the future. 

In this Sect, we describe the starting material impurities and their effect on the processing and cure reactions of TGDDM-DDS epoxies. The cure reactions are characterized by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) studies. The BF3 amine catalysts used to accelerate the cure of TGDDM-DDS epoxies are characterized by nuclear magnetic resonance (NMR) spectroscopy studies. 

Mass spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and infrared spectroscopy indicated that the cured meat pigment was mononitro-sylhemochrome. Contrary to previous reports, no evidence was found to indicate presence ofdinitro-sylheme complexes. 

Marand, E., Baker, K.R. and Graybeal, J.D., Comparison of reaction-mechanisms ofepoxy-resins undergoing thermal and microwave cure from in situ measurements of microwave dielectric-properties and infrared-spectroscopy, Macromolecules, 1992, 25, 2243. 

Abstract—The structure of films formed by a multicomponent silane primer applied to an aluminum adherend and the interactions of this primer with an amine-cured epoxy adhesive were studied using X-ray photoelectron spectroscopy, reflection-absorption infrared spectroscopy, and attenuated total reflectance infrared spectroscopy. The failure in joints prepared from primed adherends occurred extremely close to the adherend surface in a region that contained much interpenetrated primer and epoxy. IR spectra showed evidence of oxidation in the primer. Fracture occurred in a region of interpenetrated primer and adhesive with higher than normal crosslink density. The primer films have a stratified structure that is retained even after curing of the adhesive. 

O Brien and Hartman (26) studied the interface of a model system—epoxy resin, regenerated cellulose fibers—by attenuated total reflectance infrared spectroscopy. They compared spectra of the components to spectra of epoxy cured on cellulose and found for the mixture a diminished hydroxyl absorption (3,350 cm 1) and C-0 stretching (1,050 cm"1), and disappearance of the epoxy band (915 cm 1). From this they concluded that covalent bonding does occur between the epoxide groups and cellulose hydroxyls. 

The first coupling of a LINAC with infrared spectroscopy has been performed by Palmese et al. in order to study in situ kinetics of radiation-induced cationic polymerization of epoxy systems. The aim of the study is to understand the curing behavior of polymers under irradiation. A UV light source and an electron beam (10 MeV pulse width of the beam from 2.5 to 10 pm) are coupled to a portable near infrared (NIR) instrument. Briefly, a portable NIR spectrometer (Control Development Incorporated, South Bend, IN, USA) is used,... 

There are also more recent developments of other dual physio-chemical experimental methods. For example Durand et al (2006) presented a laboratory-made system that allows the coupling of dielectric analysis and Fourier-transform near-infrared spectroscopy (FT-NIR) to follow the cure of polyepoxy reactive systems. Complementary data are provided by the simultaneous dielectric analysis (the vitrification phenomenon) and near-infrared spectroscopic analysis (the extent of the reaction). 

Infrared spectroscopy continues to be one of the principal techniques for structural analysis of polymers and for identifying components of complex formulations. The distinctiveness of important vinyl, alkyl, and aryl chemical structures in the infrared such as ester, amide, nitrile, isocyanate, hydroxyls, amine, and sulfone makes it ideal for the first gross characterization of chemical types present and for following the reactions of these functional groups in curing or degradation studies. 

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