Die Chronik der Arbeitsgruppe Polymere Materialien

Veröffentlichung


P. B. Sassmann, O. Weichold

Ionics 2019

Zum Artikel→

Preparation and characterisation of ion-conductive unsaturated polyester resins for the on-site production of resistivity sensors

ABSTRACT: Ion-conductive unsaturated polyesters were synthesised from poly(ethylene oxide) and maleic anhydride for use in the development of improved methods for the structural-health monitoring of infrastructural buildings. The unsaturated polyesters (UP) were cross-linked with styrene using a redox initiator in the presence of LiClO4. Electrochemical impedance-spectroscopy was used to study the effects of initiator and styrene concentration as well as the EO:Li+ ratio. Increasing the initiator or styrene content results in an increased resistivity of the final materials. Cross-linking with styrene does not appear to cause microphase separation into pure UP and polystyrene phases, since the resulting resistivities are significantly lower than predicted by the rule of mixtures. For all temperatures under investigation (0 °C to 60 °C), the lowest resistivities were found for a EO:Li+ ratio of 50 (400 Ω·m at 22 °C), which is in accordance with previous findings. The electrical properties of the present materials are determined by diffusion controlled process in such a way polarisation prevails at high temperatures. In a proof of principle experiment, one selected UP formulation was injected into drill holes in concrete and cured at different temperatures and moisture conditions. This system reliably monitors the resistivity against an embedded reference electrode.

Veröffentlichung


M. B. Endres, O. Weichold

Carbohydrate Polym. 2018

Zum Artikel→

Sorption-active transparent films based on chitosan

ABSTRACT: In this paper we describe the preparation of alkanoic acid-based aqueous chitosan solutions, which show no sign of acid-catalysed depolymerisation over time – something commonly accompanying other preparation methods. Longer chitosan chains have previously been shown to exhibit more advantageous biological activities, and constant viscosities are essential for consistent quality in biomedical applications. Avoiding acid-catalysed depolymerisation requires careful control of the stoichiometry between the free amino groups of chitosan and the appropriate solubilising acid. Acetic and butyric acid are both suitable solubilising agents, but chitosan butyrate exhibits lower solution viscosities due to a combined electric and steric shielding of the chains.
These solutions dry into clear transparent films that remain fully water soluble and absorb up to 70 wt% of water from 90 %-RH vapour phase at 25 °C. The absorption follows simple first-order kinetics and the rate constants increase with increasing humidity up to approx. 71 %-RH, where a metastable chitosan trihydrate salt appears to be formed. Desorption is slightly faster, but more complex, as it exhibits two distinct first-order processes. In addition, films prepared in this way are thermally more stable than the usual chitosan hydrochloride.

Titelseite


A. Jung, O. Weichold

Andres Veröffentlichung „Preparation and characterisation of highly alkaline hydrogels for the re-alkalisation of carbonated cementitious materials“ wurde von Soft Matter für die Gestaltung der Titelseite ausgewählt (10/2018).

Bachelorarbeit


Lutz Burow

Wir gratulieren zum erfolgreichen Abschluss der Bachelorarbeit

Untersuchung der thermischen Eigenschaften von mit Keratin imprägnierten Holzspänen

Thermal properties of keratin-impregnated chipped wood

(10/2018)

Vortrag


O. Weichold

IBAUSIL, Weimar, 12.–14. September 2018

Polymere und Beton – Eine wilde Ehe mit Potential

Bachelorarbeit


Lena Schmitz

Wir gratulieren zum erfolgreichen Abschluss der Bachelorarbeit

Vernetzte Polyethylenglycole als Träger für ionenleitfähige Filme

Cross-linked polyethylene glycol matrix for ion-conductive films

(9/2018)

Masterarbeit


Jan Tenbusch

Diese Masterarbeit wurde extern, in Zusammenarbeit mit der Fa. Henkel durchgeführt. Wir gratulieren zum erfolgreichen Abschluss.

(8/2017)

Bachelorarbeit


Kathrin Dahm

Wir gratulieren zum erfolgreichen Abschluss der Bachelorarbeit

Synthese ethoxylierter und propoxylierter Styrole zur Herstellung ionisch leitfähiger Polyester

Synthesis of ethoxylated and propoxylated styrene for the formation of ionic conductive polyesters

(8/2018)

Bachelorarbeit


Julia Littke

Wir gratulieren zum erfolgreichen Abschluss der Bachelorarbeit

Synthese ungesättigter Polyester auf Basis von PPO

Synthesis of unsaturated polyesters based on PPO

(7/2018)

Veröffentlichung


A. Jung, O. Weichold

Soft Matter. 2018

Zum Artikel→

Preparation and characterisation of highly alkaline hydrogels for the re-alkalisation of carbonated cementitious materials

ABSTRACT: Highly alkaline hydrogels that allow the restoration of alkaline buffer in cementitious materials can be obtained from diallyldimethylammonium hydroxide. The latter must be prepared in dilute solutions and polymerised at ambient temperatures in order to avoid decomposition. Using methacrylamide as a neutral co-monomer capable of forming hydrogen bonds, the rheological properties of the gels can be adjusted over a wide range; e.g. the viscosity increases a thousandfold from 0.35 Pa·s to 4350 Pa·s by using 10 mol% methacrylamide. For the proof of principle experiments, gels with 9 mol% methacrylamide were used, which contain approx. 1.6 mol hydroxide ions per kg gel. Ion exchange between this and a neutral chloride containing gel provided an apparent diffusion coefficient of 4.12·10−7 m2 s−1 for the hydroxide ions and confirmed the transport of chloride ions into the alkaline gel. The re-alkalisation was tested on fully carbonated mortar prisms made from Portland cement. Re-alkalisation of the mortar was confirmed by the phenolphthalein test according to DIN EN 14630:2007-01 and by a control experiment with pure calcium carbonate using IR spectroscopy.

Bachelorarbeit


Jan Bandowski

Wir gratulieren zum erfolgreichen Abschluss der Bachelorarbeit

Entwicklung von Steuerungsmechanismen zur Regulierung der viskosen Eigenschaften eines PolyDADMAC-Gels

Development of mechanisms to control the viscous properties of PolyDADMAC gels

Die Arbeit wurde zusammen mit der FH Aachen, Fachbereich Chemie und Biotechnologie durchgeführt.

(4/2018)

 

Veröffentlichung


T. Juraschek, O. Weichold

J. Phys. Org. Chem. 2017; e3739

Zum Artikel→

Development of an electrochromic device triggered by the macrocell current in chloride-induced corrosion of steel-reinforced concrete

ABSTRACT: This article presents the development and characterisation of an electrochromic device and its application to detect steel corrosion in reinforced concrete. Steel corrosion inflicts an enormous annual economic damage, which could be reduced by the installation of appropriate monitoring devices. These should be simple, reliable, long lasting, and should not require service or maintenance. The present electrochromic device is constructed in such a way that it uses the macrocell current in an active, chloride‐induced corrosion element as power supply to trigger the colour change. This way, the system stays inactive until corrosion occurs. The device consists of diheptyl viologen in a liquid polymer electrolyte made from LiClO4 and poly(ethylene glycol) with Mw = 400 g mol−1. The addition of viologen lowers the resistance but causes no further changes in the electrochemical properties of the polymer electrolyte. Impedance spectra indicate ion transport rather than capacitance effects to dominate the electrochemical properties. Experiments using direct current in the microampere range show electrochromic switching times of several minutes, which is sufficient for the intended monitoring application.

Vortrag


O. Weichold

Tagung der GDCh-Fachgruppe Bauchemie, Weimar, 19. September 2017

Polymere im Bauwesen – weiche Materialien in einer harten Welt

Vortrag


A. Jung

Tagung der GDCh-Fachgruppe Bauchemie, Weimar, 19. September 2017

Hochalkalische Polymergele auf Basis von Diallyldimethylammoniumhydroxid für die Realkalisierung von Stahlbeton

ABSTRACT: Der Vortrag beschreibt die kinetische Untersuchungen der Homo- und Copolymerisation hochalkalischer Monomere zur Herstellung entsprechender Polymergele sowie den Zusammenhang zwischen der Zusammensetzung und den rheologischen Eigenschaften. Außerdem wird die Effektivität der Realkalisierung anhand des Phenolphthalein-Tests gezeigt.

Vortrag


M. Brenner

Tagung der GDCh-Fachgruppe Bauchemie, Weimar, 19. September 2017

Funktionalisierung von Faseroberflächen für textilbewehrte Elastomere

ABSTRACT: Maßgeblich für die Tragfähigkeit von textilbewehrten Strukturen ist die Leistungsfähigkeit der Grenzfläche. In zementgebundenen Systemen wird dies meist durch formschlüssige Verbindungen (z. B. mit Epoxidharz getränkte und abgesandete Carbontextilien) erreicht. In polymeren Materialien ist ein derart steifer Verbund auf Grund der kleineren E-Moduln häufig unerwünscht, bei Elastomeren sogar kontraproduktiv.

Der Vortrag berichtet über eine Untersuchung zur gezielten chemischen Funktionalisierung von Glas-, Basalt- und Carbonfasern zur Verstärkung von Chloropren und EPDM. Die Fasern wurden jeweils mit Bis[3-(triethoxysilyl)propyl]tetrasulfid (TESPT) und 3-(Mercaptopropyl)trimethoxysilan (3-MPTMS) modifiziert. Zur Applikation wurden die Substanzen mit gelöstem Elastomer versetzt und händisch auf die Fasern aufgetragen. Anschließend wurden die modifizierten Fasern in einer speziell gefertigten Form ins Elastomer einvulkanisiert und die Faser-Matrix-Adhäsion per Ausziehversuch getestet. Bei Glas- und Basaltfasern konnte eine Verbesserung des Verbunds um bis zu ca. 100 % erreicht werden, bei der Modifikation von Carbonfasern lässt sich der Verbund um ca. 50 % verbessern.

Veröffentlichung


O. Weichold, U. Antons

J. Infrastruct. Syst. 2017, 23, 04017010

Zum Artikel→

Assessing the Performance of Hydrophobing Agents on Concrete using Non-Destructive Single-Sided Nuclear Magnetic Resonance

ABSTRACT: Single-sided nuclear magnetic resonance is a nondestructive analytical technique by which the ingress behavior of hydrophobing agents as well as the properties and performance of the resulting hydrophobic layers can be assessed quantitatively. The method is used to compare the behavior of two low-molecular-weight hydrophobing agents, n-octyltriethoxysilane and i-butyltriethoxysilane, on concrete and to assess the properties of the resulting hydrophobic layers. For the octyl derivative, ingress appears to be a simple transport process without pronounced polycondensation in the liquid phase or reaction with the pore walls because the detectable amount stays rather constant during the first day of observation. In addition, the thickness of the resulting hydrophobic layer correlates well with the endpoint of the transport process. In contrast, the detectable amount of the butyl derivative is reduced to half during the first 18 h, indicating either substantial polycondensation or anchoring to the pore walls, and the hydrophobic layer is approximately 25% thicker than indicated by the ingress profiles. The different behavior could originate in differences in the molecular structure, particularly the steric demand of the alkyl substituents, although this requires a more detailed study. Both compounds proved to be excellent hydrophobing agents since the layers were found to be impermeable when kept in a shallow water bath (unidirectional transport through the layer) for more than 1 year. The results demonstrate that single-sided nuclear magnetic resonance is an excellent nondestructive tool for quality assurance when applying such protective layers.

Vortrag


T. Juraschek

EUROCORR 2017, Prag, 3. September 2017

Chemical, Non-Electronic Corrosion Indication Systems

ABSTRACT: Corrosion of the steel reinforcement in concrete causes an enormous economic damage. In particular, chloride-induced macroelement corrosion of the reinforcement is one of the bottlenecks in the service life time design of a majority of infrastructure buildings with a significant exposition to chloride. Corrosion monitoring offers a possibility to detect the onset of corrosion events and start independent restoration actions at a point, where costs can be kept at a minimum.

The presentation focusses on the testing procedure and verification of the prototype, under conditions simulating real-life corrosion events. Color change is not observed when applying zero-load currents, but occurs within minutes after raising either the potential or current to levels typical for corrosion events. The color change is persistent even after turning the power source off. We applied potential controlled current profiles as well as voltage controlled current profiles to the device, also with respect to peak current profiles to show the response of the system under realistic circumstances. Also, we investigate the influence of zero-load current and voltage events during the passive state of the reinforcement steel after passivation. Furthermore, experiments on reinforcement steel and reinforced concrete samples are shown as a proof-of-principle experiment.

Karriere


Unsere Ehemalige Elena Heß tritt zum 1.7.2017 eine Stelle bei HeidelbergCement an.

Veröffentlichung


R. Schulte Holthausen, O. Weichold

J. Infrastruct. Syst. 2017, 23, B4016006.

Zum Artikel→

Non-destructive Evaluation of Thermal Damage in Concrete by Single-Sided Nuclear Magnetic Resonance

ABSTRACT: A new technology to coat concrete with coherent layers of glass by flame-spraying is currently developed at the Institutes of Building Materials Research and Mineral Engineering of RWTH Aachen University in Germany through a joint program. A major factor influencing the pull-off strength of the flame-sprayed glass coating is thermally induced damage in the underlying concrete substrate. In this article, the authors present a nondestructive test method using single-sided 1H nuclear magnetic resonance (NMR) to evaluate the thermally induced damage in concrete specimens. The particular NMR device used in this project primarily detects water and can qualitatively assess the water content as well as the relative size of water-filled voids such as pores and cracks. To do so, the specimens are water saturated and subsequently analyzed by NMR. Changes in the NMR-signal are interpreted in terms of change in porosity and development of cracks inside the cement stone as a function of depth from the concrete surface.

Bachelorarbeit


Iva Rroshi

Wir gratulieren zum erfolgreichen Abschluss der Bachelorarbeit

Zur Untersuchung der Genauigkeit bei der Ermittlung des Bindemittelgehalts an Betonproben durch Methoden der chemischen Analytik

Investigation of the accuracy conerning the determination of the binder content of concrete samples by methods of analytical chemistry

(6/2017)

Masterarbeit


Markus Brenner

Wir gratulieren zum erfolgreichen Abschluss der Masterarbeit

Funktionalisierung von Faseroberflächen für textilbewehrte Elastomerlager

Functionalization of Fiber Surfaces for Textile-Reinforced Elastomeric Bearings

(3/2017)

Vortrag


O. Weichold

Seminar „Stadtstraßen / Ortsdurchfahrten“ des VSVI Niedersachsen e.V., ABZ Mellendorf, 25. Januar 2017

CARPET – Konfektionierter, aufrollbarer, polymerbasierter Straßenbelag

Image of fresh and hardened carpet samples

Konferenzbeitrag


T. Juraschek, O. Weichold

6th International Conference on Concrete Repair (Concrete Solutions), Thessaloniki, 2017, S. 207–211.

In-situ methods of detecting steel corrosion using permanent and non-electronic systems

ABSTRACT: Current systems for detecting corrosion of the reinforcement in concrete are realized via highly specialized systems that are commercially not available. Thus, these systems require complete technical support by the installing company. This report shows a cheap, efficient, independent, and reliable method to detect corrosion events in concrete. The detection system is based on an electrochromic device, which changes its colour upon the change of electrochemical potential caused by the corrosion process. The device is realized by a layer-by-layer setup of a transparent electrode, e. g. indium-doped tin oxide (ITO), followed by an electrochromic layer. The system is closed by a metal counter electrode. The electrochromic layer can consist of an electrochromic compound in a conducting polymer system. By connecting such elements to a series of sensors, e. g. an anode ladder, it is possible to monitor the corrosion progress and to verify the service life design of a structure.

Konferenzbeitrag


P. B. Sassmann, O. Weichold

6th International Conference on Concrete Repair (Concrete Solutions), Thessaloniki, 2017, S. 235–238.

Development of Electrically Conductive Resins for the On-Site Fabrication of Sensors for Corrosion Detection and Risk Assessment in Reinforced Concrete

ABSTRACT: Assessing the risk of corrosion in steel-reinforced concrete can be accomplished using different types of sensors such as anode ladders or multi-ring electrodes. The former are unsuitable for retrofit installations, while the latter require the use of embedding mortars to achieve conductive connections with the surrounding concrete. However, the porosity of the embedding mortar differs from that of the concrete and the retrofitting action introduces additional moisture. This interferes with resistivity and/or potential measurements and makes interpretations of the actual situation problematic. To circumvent these disadvantages, we have developed a liquid reactive polymer resin with high electrical conductivity that can be used to fabricate sensors directly inside drill holes. The mixture solidifies in a short time and its adhesive properties provide an excellent conductive connection to the concrete walls. The resin contains no water so that reliable values can be obtained immediately after solidification. By changing the additives both resistivity and potential sensors can be obtained. The mixture is cheap so that large sensor networks can be installed at reasonable costs. Such networks are ideal for the precise localization of corrosion events and more importantly for risk assessment in steel-reinforced structures.

 

Vortrag


O. Weichold

1. VDI-Fachkonferenz „Betrieb und Instandhaltung industrieller Kanalnetze“, Frankfurt, 14.–15. Dezember 2016

Beständigkeit bei aggressiven Medien – heiß, ätzend, korrosiv!

Vortrag


O. Weichold

nuBau – 3. Tagung Nutzerorientierte Bausanierung, Weimar, 30. November – 1. Dezember 2016

Neue Methoden zur Auswertung von Sw-ρ-Beziehungen

ABSTRACT: Der spezifische elektrische Widerstand des Betons wird häufig herangezogen, um Aussagen über die Dauerhaftigkeit von Stahlbetonbauwerken zu treffen. Das Ziel der vorgestellten Untersuchungen besteht darin, Wassergehalt-Widerstandsbeziehungen in Abhängigkeit von relevanten Strukturparameten des Betons zu charakterisieren. Hierzu wurde ein Ansatz auf Basis von Archies Gesetz gewählt, dessen Ergebnisse vorgestellt und mit dem üblicherweise velwendeten Modell verglichen werden. Es wird versucht, ausgewählte Parameter mit den Eigenschaften des Porensystems der Betone zu konelieren und so die Möglichkeiten des vorgestellten Ansatzes aufzuzeigen.

Vortrag


P. B. Sassmann

2nd International Conference on the Chemistry of Construction Materials (ICCCM), München, 10.–12. Oktober 2016

Development of ion- conductive polymer resins for the on-site fabrication of corrosion sensors

ABSTRACT: Assessing the corrosion risk in steel-reinforced concrete can be accomplished by implementing monitoring systems. For retrofit installations the electrically conductive connection of sensors and surrounding concrete is currently realised with cement-based embedding mortars. The use of such aqueous systems changes the moisture content of the concrete close to the sensor, which interferes significantly with resistivity and/or potential measurements and makes interpretations of the measured values problematic.

To circumvent these disadvantages, we developed a liquid, reactive, non-aqueous polymer resin with high electrical conductivity that can be used to fabricate sensors directly inside drill holes. This way, a close contact between sensor and the concrete walls is automatically provided. Since the polymer resin is not aqueous, the moisture balance of the old concrete is not altered so that reliable values can be obtained immediately after solidification.

Buchbeitrag


J.-P. Lecomte, O. Weichold

in Y. Liu (Ed.), Silicone Dispersions (Surfactant Science Series Vol. 159), CRC Press, Boca Raton, 2016, S. 301–331.

 

Silane-based Water Repellents for Inorganic Construction Materials

Masterarbeit


Pia B. Sassmann

Wir gratulieren zum erfolgreichen Abschluss der Masterarbeit

Ionenleitende ungesättigte Polyester zur Ankopplung von Zulagekathoden in Beton

Ion-conductive unsaturated polyester for contacting galvanic couples in concrete

(5/2016)

Veröffentlichung


D. Heinze, Th. Mang, C. Popescu, O. Weichold

Thermochim. Acta 2016, 637, 143–153

Zum Artikel→

 

 

Effect of side chain length and degree of polymerization on the decomposition and crystallization behaviour of chlorinated poly(vinyl ester) oligomers

ABSTRACT: Four members of a homologous series of chlorinated poly(vinyl ester) oligomers CCl3–(CH2CH(OCO(CH2)mCH3))n–Cl with degrees of polymerization of 10 and 20 were prepared by telomerisationusing carbon tetrachloride. The number of side chain carbon atoms ranges from 2 (poly(vinyl acetate) to 18 (poly(vinyl stearate)). The effect of the n-alkyl side chain length and of the degree of polymerizationon the thermal stability and crystallization behaviour of the synthesized compounds was investigated.All oligomers degrade in two major steps by first losing HCl and side chains with subsequent breakdownof the backbone. The members with short side chains, up to poly(vinyl octanoate), are amorphous andshow internal plasticization, whereas those with high number of side chain carbon atoms are semi-crystalline due to side-chain crystallization. A better packing for poly(vinyl stearate) is also noticeable.The glass transition and melting temperatures as well as the onset temperature of decomposition areinfluenced to a larger extent by the side chain length than by the degree of polymerization. Thermalstability is improved if both the size and number of side chains increase, but only a long side chaincauses a significant increase of the resistance to degradation. This results in a stabilization of PVAc sothat oligomers from poly(vinyl octanoate) on are stable under atmospheric conditions. Thus, the way todesign stable, chlorinated PVEs oligomers is to use a long n-alkyl side chain.

Bachelorarbeit


Tim Kurschildgen

Wir gratulieren zum erfolgreichen Abschluss der Bachelorarbeit

Einfluss der Copolymerisation funktioneller Monomere im Porenraum auf die mechanischen Eigenschaften von Mörtel

Copolymerisation of functional monomers in the pore system of mortars and its influence on the mechanical properties

 (4/2016)