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The curing process of epoxy affects the chemical structure of the final network so mechanical and physical properties of the polymeric matrix for a composite may be modified according to the polymerisation conditions. This paper describes the ambiguity in assignment of reference bands to follow the cure of poly‐epoxy reactive systems using a laboratory‐made system which allows the coupling of dielectric analysis and Fourier Transform Near Infrared Spectroscopy (FTNIR). The dielectric measurements were obtained using interdigitated electrode. In situmonitoring of extent of reaction was carried out from room temperature up to 160 °C using fibre‐optic FTNIR spectroscopy. For the DGEBA/MCDEA system the epoxy band at 6060 cm−1was chosen in preference to the band at 4530 cm−1as representative of the epoxy function evolution during polymerisation because a small unknown peak probably due to the hardener appears in the 4530 cm−1region. The bands at 4620 and 4680 cm−1assigned to aromatic combination bands and widely used as reference bands are not unique for this formulation hence the band at 5980 cm−1is used as reference. The Principal Components Analysis (PCA) shows clearly also that the bands at 4620 and 4680 cm−1vary during the polymerisation. Surprisingly, the band at 4530 cm−1is equivalent to the one at 6060 cm−1to calculate the conversion rate. It is probably due to the fact that the hardener band near 4530 cm−1follows the same behaviour as the epoxy band at 4530 cm−1.

In this paper, a laboratory-made system which allows the coupling of dielectric analysis and Fourier transform near infrared spectroscopy (FT-NIR) to follow the cure of polyepoxy reactive systems is presented. The dielectric measurements were obtained using an interdigitated electrode. In situmonitoring of the extent of the reaction was carried out from room temperature up to 160°C using fibre-optic FT-NIR spectroscopy. The appliance for simultaneous measurement is described and the advantages and limitations are briefly discussed. Dielectric analysis and near infrared spectroscopy are complementary since the former can detect the vitrification phenomenon and the latter can give access to the extent of the reaction. When combined, the two spectroscopies can detect indirectly, after calibration, the extent of a reaction from the electric degree of transformation and vice versa with the help of chemometrics.

In this paper, a laboratory-made system which allows the coupling of dielectric analysis and Fourier transform near infrared spectroscopy (FT-NIR) to follow the cure of polyepoxy reactive systems is presented. The dielectric measurements were obtained using an interdigitated electrode. In situ monitoring of the extent of the reaction was carried out from room temperature up to 160°C using fibre-optic FT-NIR spectroscopy. The appliance for simultaneous measurement is described and the advantages and limitations are briefly discussed. Dielectric analysis and near infrared spectroscopy are complementary since the former can detect the vitrification phenomenon and the latter can give access to the extent of the reaction. When combined, the two spectroscopies can detect indirectly, after calibration, the extent of a reaction from the electric degree of transformation and vice versa with the help of chemometrics.

Oriented poly(ethylene‐2,6‐naphthalate) (PEN) has been characterised by polarised FT‐IR spectroscopy to determine the structural angles of the transition moments to the molecular chain axis. The bands at 1130 cm−1, 1142 cm−1and 1602 cm−1, which have been previously assigned as having their transition dipole moments parallel to the chain axis, are confirmed as parallel bands. Bands at 767 cm−1and 831 cm−1are confirmed as perpendicular bands. However the band at 1708 cm−1which has previously been assigned as a perpendicular band, is shown here to have its transition moment at 72° to the molecular axis.

The dynamic mechanical and dielectric behaviours of Polypropylene (PP) and (Ethylene‐Vinyl Acetate) Copolymer (EVA) blends are reported as a function of the morphology. For EVA contents lower than 20%, blends show the two‐phase morphology characteristic of immiscible blends, with spherical EVA droplets finely dispersed in the PP matrix. After stretching in the molten state, the morphology of EVA fibers is observed. Mechanical Relaxation Spectroscopy display three relaxation processes: the EVA and PP α‐relaxations associated to the glass transitions and a β‐transition corresponding to a PP crystalline phase relaxation. The PP α‐relaxation shifts to higher temperatures when EVA presents a fiber morphology, corresponding to a decrease of PP chain mobility since it is hindered by the reinforcement effect of EVA fibers. Quite different results are obtained by DRS analysis. In blends containing EVA fibers, only one main relaxation associated to the EVA α‐transition is observed whereas one additional relaxation can be noticed in the blends containing EVA droplets. This new relaxation might be assigned to interfacial polarization effects, phenomena that are sometimes observed in heterogeneous polymer blends when a low content of one polar component is embedded in a non conductive matrix. In this case, the occurrence of a characteristic interfacial polarization relaxation appears to be correlated to the accessible experimental frequency.

γ-irradiation of ethylene–propylene diene monomer (EPDM) elastomers under oxidant atmosphere was carried out in order to change their mechanical and dielectric behaviour. Three different formulations of EPDM (70 wt% ethylene, 28 wt% propylene; diene monomer: 2 wt% norbornene) were studied: a non-crosslinked EPDM terpolymer, a crosslinked EPDM and a crosslinked EPDM stabilized with an antioxidant. Dielectric and mechanical relaxation show a β-sub-glass relaxation at about −120 °C (1 Hz) and an α-relaxation at −15 °C (1 Hz) associated with the glass transition but influenced by the effects of irradiation. The local mobility associated with the β-relaxation is only weakly influenced by γ-irradiation up to 450 kGy. The α-process is shifted to higher temperatures as a result of crosslinking and changes in the semicrystalline structure. The amplitude of the dielectric α-process increases as a result of the formation of oxidized species during irradiation under oxygen. In contrast, the mechanical α-relaxation amplitude decreases as a result of physical and chemical cross-linking. It was shown that the main factors that determine the crosslinking/chain scission balance are (1) the presence of oxygen together with the irradiation dose, (2) the dose rate and (3) the initial crosslink density of the EPDM material. As a result, the individual contribution of crosslinking and crystallization, and therefore the understanding and prediction of the properties after γ-irradiation can only be deduced after comparison of the polymer behaviour below and above its melting temperature. Copyright © 2004 Society of Chemical Industry