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Riechers J.,Herrenknecht Formwork Technology GmbH | Lueghamer A.,AGRU Kunststofftechnik GmbH | Recher G.,Telene SAS
ITA-AITES World Tunnel Congress 2016, WTC 2016

Despite comparable standards with regards to protective membranes and gaskets, specified in tender documents, different methodologies are known and in use for protection and hydraulically optimization of segmental lined tunnels, achievable in two passes or one pass. Based on detailed monitoring of key materials and systems involved, the combi segments type II HDPE, an adaptable protective system for constructions on one pass, has been developed. The objection of this paper was to discuss this integral protective lining system in respect of material characteristics and its adaptability to both project and customers' demands. Reviewed performances show outstanding capabilities of the Liner System and its potential for future feature extensions. After realization of first reference projects applying the new combi segments lining panels, further publications will follow including practical experience reports of panel fabrication, segment production and tunnel installation. Copyright © (2016) by the Society for Mining, Metallurgy and Exploration. All rights reserved. Source

Grabmayer K.,Johannes Kepler University | Beissmann S.,Johannes Kepler University | Wallner G.M.,Johannes Kepler University | Nitsche D.,AGRU Kunststofftechnik GmbH | And 4 more authors.
Polymer Degradation and Stability

Specimens with varying thickness of different polypropylene random copolymer formulations were oven aged in hot air at 135 °C. Besides macro-sized specimens die-punched from 2 mm thick extruded sheets, 50 μm, 200 μm and 500 μm thick micro-sized specimens, cut edgewise from the sheets by an automated planing procedure, were investigated. The formulations included a base stabilized reference compound and four formulations prepared with systematically varied additional contents of the primary antioxidants Naugard 445 and Irganox 1010 and the secondary antioxidants Irganox PS-800 and Irganox PS-802. Aging characterization was performed by tensile testing, differential scanning calorimetry and high performance liquid chromatography employing strain-at-break, oxidation onset temperature (OOT) and the content in phenolic antioxidants as aging indicators, respectively. Aging characterization revealed a systematic thickness dependence of the embrittlement time and the rate of the reduction in OOT as well as the reduction of phenolic antioxidants. The 50 μm thick specimens exhibited embrittlement times between 50% and 65% of the 2 mm thick macro-sized specimens. For low thicknesses, a high surface to volume ratio is presumably responsible for the fast physical loss of antioxidants, while for thick specimens, physical stabilizer loss is limited by the rate of stabilizer diffusion from the bulk to the surface. Hence, thicker specimens showed longer embrittlement times. Regarding stabilizer loss, Naugard 445 and Irganox PS-800 exhibited significantly higher loss rates than Irganox 1010 and Irganox PS-802. © 2014 Elsevier Ltd. All rights reserved. Source

Grabmayer K.,Johannes Kepler University | Wallner G.M.,Johannes Kepler University | Beissmann S.,Johannes Kepler University | Schlothauer J.,Humboldt University of Berlin | And 5 more authors.
Polymer Degradation and Stability

Two commercial polyethylene grades were oven-aged at 95 °C and 115 °C for more than 1000 h. Aging characterization was performed by laser-induced photoluminescence spectroscopy (λEx = 375 nm), laser confocal microscopy, infrared (IR) spectroscopy, high performance liquid chromatography, differential scanning calorimetry and tensile testing. Photoluminescence increased significantly upon oven-aging, especially at 115 °C. The maximum of emission was around 450 nm. Decreasing oxidation onset temperatures (DSC) and stabilizer concentrations (HPLC) indicate oxidation-induced changes in the materials that are in agreement with increasing photoluminescence. IR spectroscopy and tensile testing results showed no global oxidative degradation and no premature failure. Hence, the materials were still in the induction period of oxidative degradation. The evolution of photoluminescence is presumably related to the formation of oxygenated groups like α,β-unsaturated carbonyl groups. The investigations clearly indicated that photoluminescence spectroscopy is a sensitive method to monitor aging-induced changes within the induction period. © 2014 Elsevier Ltd. All rights reserved. Source

Maringer L.,Johannes Kepler University | Roiser L.,Johannes Kepler University | Wallner G.,Johannes Kepler University | Nitsche D.,AGRU Kunststofftechnik GmbH | Buchberger W.,Johannes Kepler University
Polymer Degradation and Stability

Within this work, UV-initiated interaction mechanisms between the phenolic antioxidant Irganox 1330 and nine commercially used hindered amine light stabilizers (HALS) were successfully studied using high-performance liquid chromatography (HPLC) coupled to UV and high-resolution mass spectrometric detection (MS). An analytical evaluation of the stabilizer performances in the polypropylene-mimicking solvent squalane revealed that all investigated HALS exhibited a strong synergism when combined with the phenolic antioxidant. Up to now, the synergistic interaction was described as a result of the hydrogen transfer from a hydroxylamine derived from HALS to the oxidized form of a primary antioxidant, whereby the phenol is regenerated. Investigations on degradation products, however, indicated that the proposed interaction mechanism cannot be applied to a sterically hindered phenol such as Irganox 1330. Instead, a completely new stabilization mechanism of phenolic antioxidants in the presence of HALS, involving the formation of quinoid derivatives, was discovered and confirmed by using a model compound. © 2016 Elsevier Ltd Source

Grabmayer K.,Johannes Kepler University | Wallner G.M.,Johannes Kepler University | Beissmann S.,Johannes Kepler University | Braun U.,BAM Federal Institute of Materials Research and Testing | And 5 more authors.
Polymer Degradation and Stability

Two commercial polyethylene grades were exposed to water at elevated temperatures and enhanced oxygen pressure. To characterize their aging behavior laser-induced photoluminescence spectroscopy was applied. Additionally, aging characterization was performed by established methods such as tensile testing, infrared (IR) spectroscopy, high performance liquid chromatography (HPLC), differential scanning calorimetry (DSC) and UV-VIS spectroscopy. During the initial stages of aging, the overall concentration of phenolic antioxidants as well as oxidation onset temperatures decreased exponentially. Simultaneously, significant discoloration due to the formation of conjugated degradation products from phenolic antioxidants (e.g., quinone methides) was detected. After the consumption of antioxidants, photoluminescence started to grow continuously presumably due to the formation of photoluminescent unsaturated carbonyls. In the final stages of aging, embrittlement of the materials as characterized by the degradation of mechanical properties (i.e., loss in ductility) coincided with rising carbonyl index values as well as an increase in crystallinity due to chemicrystallization. Between integrated photoluminescence intensity and carbonyl index, a linear correlation was established. In the induction period, the photoluminescence method exhibited a significantly higher sensitivity to reflect aging induced material changes. © 2014 Elsevier Ltd. All rights reserved. Source

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