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Bibliographic record number: 346737

Journal

Authors: Mahović Poljaček, Sanja; Gojo, Miroslav; Risović, Dubravko; Furić, Krešimir
Title: Printing plates' porous structure characterization by impedance spectroscopy
Source: Book of Abstracts of the 1st Regional Symposium on Electrochemistry of South-East Europe / Horvat-Radošević, Višnja ; Mandić, Zoran ; Gojo, Miroslav (ed). - Rovinj : Croatian Society of Chemical Engineers , 2008. 411-412 (ISBN: 978-953-6894-33-8).
Meeting: Regional Symposium on Electrochemistry of South-East Europe (1 ; 2008)
Location and date: Rovinj, Hrvatska, 04.-08.05.2008
Keywords: impedance spectroscopy; printing plates; structure characterization
Abstract:
Size and quality of the grained microstructure, i.e. porous layer of the lithographic printing plate has most significant influence on the quality of the imprints and durability of the printing plates [1]. This structure is obtained by electrochemical processes of graining and anodic oxidation [2-5], resulting in formation of specific anodic layer on an aluminium foil which consists of a thin non-porous compact layer (barrier layer) and an outer extremely porous layer. In this study we present the results of application of SEM and EIS in characterization of the changes in printing plates' oxide layer induced by processing in alkaline solutions of different processing age. SEM micrographs of the investigated printing plate samples were obtained with JEOL JMS T300 scanning electron microscope, while the EIS measurements were performed in an unstirred and aerated 3.5% (w/w) K2SO4 solution at 25°C in a three-electrode electrochemical cell. EIS spectrum was measured over the frequency range from 10 mHz to 64 kHz under controlled potentionstatic conditions using using an EG&G Lock in Amplifier Type 5210 in combination with an EG&G Potentiostat/Galvanostat Type 263 A at an open circuit potential. Capacitance and resistance data were obtained by software PowerSine EIS Software Equivalent Circuit [6]. The results of the EIS measurements and analysis of equivalent circuits' capacitance and resistance behavior, as well as SEM micrographs of the investigated samples indicate that the surface structures of different types of lithographic printing plates and their change due to processing are different and type-related. Micro-structural characterization of nominally equivalent surfaces of the printing plates which can be used in the same reproduction process has shown totally different behavior and surface structure transformation during the alkaline processing. The observed changes also depend on the age of processing solution. According to the results of the SEM micrographs analysis and corresponding EIS measurements on the aluminium oxide films it can be concluded that during the plate processing the observed surface structural changes are probably induced by two different mechanisms. The first one is the degradation and smoothening of the rough surface structure of the aluminium oxide layer and the second one is the chemical reaction of the aluminium oxide with alkaline solution during the chemical processing. The second mechanism is probably a consequence of the reaction of anhydrous aluminium oxide structure which adsorbs water from alkaline solution resulting in a sealing process. Similar changes of the anodic films on aluminium have been reported previously [7, 8]. The equivalent circuit models corresponding to the anodized layer and to the anodized sealed layer were proposed and used in interpretation of experimental results. Thus it was demonstrated that the application of SEM and EIS methods in investigation of surface structural properties of aluminium printing plate provides new insight and enables tracking and characterization of processing induced structural changes that are of primary significance for the performance of the printing plates.
Type of meeting: Poster
Type of presentation in a journal: Abstract
Type of peer-review: International peer-review
Project / theme: 128-1281957-1958, 098-0982904-2898, 128-1201785-2228, 098-0982915-2899
Original language: ENG
Category: Znanstveni
Research fields:
Physics,Graphic technology
Contrib. to CROSBI by: mgojo@grf.hr (mgojo@grf.hr), 9. Svi. 2008. u 12:15 sati



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