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The purpose of this paper is to investigate a new group of chemical compounds as accelerators (1-imidazole derivatives – tertiary amines) for curing of isocyanate-epoxy…
The purpose of this paper is to investigate a new group of chemical compounds as accelerators (1-imidazole derivatives – tertiary amines) for curing of isocyanate-epoxy resin matrix. During heating no reaction between epoxy group and active hydrogen in presence 1-substituted imidazole derivatives was reported.
The influence of accelerator type and content on curing process, thermal stability and chemical structure of hardened resin was determined using temperature modulated differential scanning calorimetry, dynamic mechanical analysis, heat deflection temperature, thermogravimetry (modulated and by activation energy – Ozawa method) and Fourier transform infrared spectroscopy. Additionally, the shear strength of epoxy compositions used as aluminium joints, at ambient and elevated temperature was determined.
With catalyst content increase the oxazolidone or isocyanurate rings content decreased, indicating enhanced density of cross-linking and thermal resistance. For all imidazole derivatives used (i.e. 1-methylimizadole, 1-ethylimidazole and 1-butylimidazole) accelerating of the curing process was observed (significant decrease of the curing start temperature was reported). The thermal resistance and shear strength was improved with accelerator content (increase of isocyanurate rings amount, and consequently oxazolidone ones).
Introducing of a new group of chemical compounds as new catalysts to isocyanate-epoxy resin material resulted in curing process acceleration, irrespectively of the imidazole derivative type.
– The purpose of this paper is to present a system for automatic recognition of defects detected in non-conductive polymer composites using pulsed terahertz imaging.
The purpose of this paper is to present a system for automatic recognition of defects detected in non-conductive polymer composites using pulsed terahertz imaging.
On the beginning, non-destructive evaluation of composites using electromagnetic waves in terahertz frequency is shortly introduced. Next automatic defects recognition (ADR) algorithm is proposed, focussing on new features calculation. Dimensionality of features space is reduced by using principal component analysis. Finally, results of basalt fiber reinforced composite materials inspection and identification using artificial neural networks is presented and discussed.
It is possible to develop ADR system for non-destructive evaluation of dielectric materials using pulsed terahertz technique. New set of features in time and frequency domains is proposed and verified.
ADR in non-destructive testing is utilized in case of digital radiography and ultrasonic testing. Terahertz inspection with pulsed excitation is reported as a source of many useful information about the internal structure of the dielectric material. Up to now ADR based on terahertz non-destructive evaluation systems was not utilized.