Epoxy near-infrared spectroscopy

The best way to elucidate the reaction path is to follow the evolution of as many independent species and functional groups as possible. For example, analysis of the epoxy-amine reaction following the simultaneous evolution of epoxy and primary amine groups by near infrared spectroscopy (NIR) simultaneous determination of the conversion of double bonds belonging to unsaturated polyester (UP) and styrene (S) using FTIR, as shown in Fig. 5.13 (Yang and Lee, 1988) determination of the evolution of the concentration of free radicals using ESR, as shown in Fig. 5.14 (Tollens and Lee, 1993). 

Many different methods can be used to measure the degree of crosslinking within an epoxy specimen. These methods include chemical analysis and infrared and near infrared spectroscopy. They measure the extent to which the epoxy groups are consumed. Other methods are based on the measurements of properties that are directly or indirectly related to the extent and nature of crosslinks. These properties are the heat distortion temperature, glass transition temperature, hardness, electrical resistivity, degree of solvent swelling and dynamic mechanical properties, and thermal expansion rate. The methods of measurement are described in Chap. 20. 

Epoxy Resins by Near-Infrared Spectroscopy", SPE Transactions... 

Mijovic, J. Andjelic, S. Yee, C.F.W. Bellucci, F. Nicolais, L. (1995). A study of reaction kinetics by near infrared spectroscopy 2. Comparison with dielectric spectroscopy of model and multifunctional epoxy/amine. Macromolecules, Vol.28, No.8, (April 1995), pp. 2797-2806, ISSN 0024-9297. 

Xu, L.S. Schlup, J.R. (1998). Etherification versus amine addition during epoxy resin amine cure An in situ study using near-infrared spectroscopy. Journal of Applied Polymer Science, Vol.67, No.5, 0anuary 1998), pp. 895-90, ISSN 0021-8995. 

No.8, 10th April 1995, p.2797-806 STUDY OF REACTION KINETICS BY NEAR-INFRARED SPECTROSCOPY. H. COMPARISON WITH DIELECTRIC SPECTROSCOPY OF MODEL AND MULTIFUNCTIONAL EPOXY/ AMINE SYSTEMS... 

Molecular structure of epoxy resins. Infrared spectroscopy (IR) is used to determine the epoxide content of resins as well as their structure. A compilation of IR spectra of uncured resins has been published (86) and their use in quality control and identification of components of resin blends has been described. Recently, near IR (NIR) has emerged as a useful tool to characterize epoxy resins (87). 

Detailed near-infrared spectra of PET exposed to different relative humidities indicated three different subbands of the first overtone of water at 7080 cm 7010 cm and 6810 cm The comparison with the water spectmm of bulk water suggested that most of the water is only weakly bonded with PET (89). The analysis of difference spectra of dry nylon and nylon exposed to different humidities, indicated that there were distinct populations of hydrogen-bonded water in it (90). Recently, Musto et al. (91) investigated the nature of molecular interactions of water in epoxy resins by means of near-infrared spectroscopy as proposed by Eukuda et al. (89,90). They found three subbands at 7076 cm 6820 cm and 6535 cm evidencing two kinds of water adsorbed in the polymer (mobile water localized in micro vide and water molecules firmly bonded to the network). However, hydroxyl groups of epoxy may complicate the analysis of water content in polymers because they absorb also in the same overtone region as water. 

B. Chabert, G. Lachenal C. Vinh-Tung. Epoxy resins and epoxy blends studied by near infrared spectroscopy. Mocmmo/Symp 94 145-158, 1995. 

BUlaud, C., R. Legras, and V. Carher, Quantitative Analysis of Epoxy Resin Cure Reaction A Study by Near-Infrared Spectroscopy. A/ / /. Spectrosc., 2002. 56 1413-1421. 

Kortaberria, G., et al.. Curing of an Epoxy Resin Modified with Poly(Methylmethacrylate) Monitored by Simultaneous Dielectric/Near Infrared Spectroscopies. Europ. Polym, J., 2004.40 129-136. Mijovic, J., et al.. Interplay of Segmental and Normal Mode Dynamics in Polymer Networks Undergoing Chemical Cross-Linking. Epoxy/Amine-Terminated Linear and Stai PPO Eormnlations. Macmmolecules, 2003. 36 4589-4602. 

Wang Q, Storm BK, HoumoUerLP. Study of the isothermal curing of an epoxy prepreg by near-infrared spectroscopy. J Appl Polym Sci 2003 87 2295-2305. 

The amine cure of Hexcel 8552 epoxy resin, for use as the matrix in carbon fibre-reinforced composites for application in aircraft construction, was monitored by near-infrared spectroscopy. This technique was validated by comparison of the results with those obtained by modulated DSC. 18 refs. 

R Musto, M. Abbate, G. Ragosta and G. Scarinzi, A smdy by Raman, near-infrared and dynamic-mechanical spectroscopies on the curing behaviour, molecular structure and viscoelastic properties of epoxy/anhydride networks, Polymer, 48, 3703-3716 (2007). 

Many investigations of the molecular structure of thin films formed by y-APS deposited onto inorganic substrates from aqueous solutions have been carried out. Ondrus and Boerio [2] used reflection-absorption infrared spectroscopy (RAIR) to determine the structure of y-APS films deposited on iron, 1100 aluminum, 2024 aluminum, and copper substrates from aqueous solutions at pH 10.4. They found that the as-formed films absorbed carbon dioxide and water vapor to form amine bicarbonate salts which were characterized by absorption bands near 1330, 1470, 1570, and 1640 cm-1. y-APS films had to be heated to temperatures above about 90°C in order to dissociate the bicarbonates, presumably to free amine, carbon dioxide, and water. Since the amine bicarbonates failed to react with epoxies, the strength of adhesive joints prepared... 

Commercial cylindrical quartz cells can be adapted for gas-phase work as illustrated in Fig. 9.18. Such a cell finds use in the near infrared for the determination of overtone vibrational frequencies, and also in visible and ultraviolet spectroscopy. A much less expensive cell which is adequate for most gases may be constructed from Pyrex along the lines of the cell shown in Fig. 9.18. Quartz windows may then be attached by epoxy resin. A cell which is filled from a conventional vacuum line will generally contain mercury vapor which absorbs at 2537 A. Once the origin of this absorption is recognized, it causes little difficulty because of its narrow bandwidth. 

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,... 

Musto, P. Mascia, L. Ragosta, G. Scarinzi, G. Villano, P. (2000). The transport of water in a tetrafunctional epoxy resin by near-infrared Fourier transform spectroscopy. Polymer, Vol. 41, No.2, Qanuary 2000), pp.565-574, ISSN 0032-3057. 

Poisson, N. Lachenal, G. Sautereau, H. (1996). Near- and mid-infrared spectroscopy studies of an epoxy reactive system Vibrational Spectroscopy, Vol.l2, No.2, (October 1996), pp.237-247, ISSN 0924-2031. 

---