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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Hyperstern-Polymere mit hochverzweigten Kernen und polaren Armen - Ihre Synthese, Charakterisierung und Anwendung als Reaktivbinder in Epoxy-basierten Photo- und Thermolacken

Däbritz, Frank 17 October 2011 (has links)
Diese Dissertation beschreibt die Synthese und Charakterisierung neuartiger Hyperstern-Polymere (HSP) und deren Funktion als Reaktivbinder in Epoxy- bzw. PUR-Harzen. Hyperstern-Polymere sind Hybride aus hochverzweigten (hvz) und linearen Polymeren. Sie können über ihre reaktiven OH-Gruppen als multifunktionelle hochverzweigte Quervernetzer kovalent in ein kationisch härtendes Epoxyharz einbinden und thermische sowie thermomechanische Eigenschaften verbessern.:Theoretischer Teil Einleitung und Aufgabenstellung Grundlagen 1 Polymeraufbau 1.1. Radikalische Polymerisationen 1.1.1. Kontrolliert radikalische Polymerisation 1.1.2. NMRP 1.1.3. ATRP 1.1.4. RAFT 1.2. Anionische Polymerisation 1.3. Kationische Polymerisation 1.3.1. CROP von Oxazolinen 1.4. Koordinative Polymerisationen 2 Verzweigte Polymerarchitekturen 2.1. Dendritische Polymere 2.1.1. Dendrimere 2.1.2. Hochverzweigte Polymere 2.1.2.1 SCVP 2.1.3. Dendrigrafts 2.1.4. Dendronisierte Polymere 2.2. Spezielle Polymerarchitekturen 2.2.1. Hyperstern-Polymere (HSP) 3 Lacke 3.1. Lösungsmittelhaltige Lacke 3.1.1. Chemisch härtende Lacke 3.1.2. Physikalisch trocknende Lacke 3.2. Wässrige Lacke 3.3. Lösungsmittelfreie Lacke 3.3.1. Strahlenhärtende Lacke 3.3.2. Pulverlacke 3.4. Aliphatische Epoxylacke 3.4.1. UV-Härtung 3.4.2. Thermische Härtung 3.4.3. Thermische Härtung klassischer 2K-Polyepoxid-Lacke 3.5. 2K-PUR-Lacke 3.6. Aktuelle Herausforderungen 3.7. Wissenschaftliche Konzepte zur Schlagzähmodifizierung von Lacken Diskussion und Ergebnisse 4 Synthese hochverzweigter Makroinitiatoren 4.1. Polyester-Makroinitiatoren PE-MI1 und PE-MI2 4.1.1. Polyester-Kern (PE-OH) 4.1.2. Makroinitiatoren für die Oxazolinpolymerisation (PE-MI1) 4.1.3. Makroinitiatoren für die ATRP von Methacrylaten (PE-MI2) 4.2. Poly(vinylbenzylchlorid)-Makroinitiator (PVBC) 5 Hypersterne mit POxa-Armen 5.1. Lineare Polyoxazolin-Modellverbindungen (POxa) 5.1.1. Test der Initiatorfunktionen 5.1.2. Einfluss der Mikrowelle 5.1.3. Terminierung (Capping) 5.1.4. Polymerisation OH-tragender Oxazoline 5.1.5. Adamantan-funktionalisierte Polyoxazoline 5.2. Hypersterne aus Polyester-Kern sowie Polyoxazolin-Armen: PE-g-POxa 5.2.1. Einführung von OH-Gruppen über die Terminierung 5.2.2. Einführung von OH-Gruppen über die Wiederholeinheiten 5.3. Hypersterne aus Polyvinylbenzylchlorid-Kern sowie Polyoxazolin-Armen: PVBC-g-POxa 5.3.1. Modellinitiatoren 5.3.2. Einführung von OH-Gruppen über die Wiederholeinheiten 5.4. Ausblick: Arm first-Strategie 6 Hypersterne mit Polymethacrylat-Armen 6.1. Hypersterne aus Polyvinylbenzylchlorid-Kern sowie Polymethacrylat-Armen: PVBC-g-PHEMA 6.2. Hypersterne aus Polyester-Kern sowie Polymethacrylat-Armen: PE-g-(PMMA-b-HEMA) 7 Hypersterne als Quervernetzer-Additive in Lacken 7.1. PVBC-g-POxa in Epoxyharz 7.1.1. Thermische Härtung 7.2. PE-g-P(MMA-b-HEMA) in Epoxyharz 7.2.1. UV-Härtung 7.2.2. Thermische Härtung 7.3. PE-g-P(MMA-b-HEMA) in 2K-PUR-Harz Zusammenfassung – Ausblick Experimenteller Teil 8 Geräte, Methoden und Chemikalien 9 Synthesen 9.1. Monomere, Capper, Niedermolekulare Substanzen 9.2. Lineare Polyoxazoline 9.2.1. Niedermolekulare CROP-Initiatoren 9.2.2. Lineares Poly(2-methyloxazolin) (PMeOxa) 9.2.3. Adamantan-funktionalisierte Poly(2-methyloxazoline) 9.2.4. Lineare Poly(2-ethyloxazoline) 9.2.5. NMR-Modellverbindungen für PVBC-Kern 9.3. Hochverzweigte Polymere und Makroinitiatoren 9.4. Hyperstern-Polymere mit POxa-Armen 9.5. Hyperstern-Polymere mit PAlkMA-Armen 9.6. Lackproben Abkürzungsverzeichnis Literaturverzeichnis Publikationsliste
22

Modified Phenol-Formaldehyde Resins for C-Fiber Reinforced Composites: Chemical Characteristics of Resins, Microstructure and Mechanical Properties of their Composites

Kim, Young Eun 06 January 2011 (has links) (PDF)
This work correlates the chemistry of phenol-formaldehyde (PF) resins, its functionalities with their microstructural and mechanical properties in composite materials. The main focus is put on the development of the pores in dependence on the chemical composition of the resins and their influence on the structure of the material. Chemical characteristics of the synthesized resins are analyzed and physical/mechanical properties of the matrices based on PF resins are determined. Differences in the chemical properties are detected e.g. by FT-IR and NMR spectroscopy. They indicate the existence of similar molecular basic structure units, but different network conditions of the resins. DSC investigations point on different reaction mechanisms and temperatures; they reveal also their changed thermal behavior. The bulk matrix behavior differs from that of the composite based on the same resin due to the three dimensional stress and strain fields in the composites. The structure of the CFRP composites is strongly depended on the fiber/matrix interaction. The fiber matrix bonding (FMB) strength controls the load transfer via shear forces and therefore the segmentation of the fiber bundles.
23

Palynologische Untersuchungen zur Geschichte von Umwelt und Besiedlung im südwestlichen Harzvorland (unter Einbeziehung geochemischer Befunde) / Pollenanalytical studies on environmental andsettlement history of the southwestern part of the harz mountain foreland (including geochemical results)

Begemann, Ina 06 November 2003 (has links)
No description available.
24

Erdfallablagerungen des südlichen Harzvorlandes / Archive der Umweltgeschichte der letzten Jahrtausende / Sediments in Karst Sinkholes of the southern Harz foreland / Archives for Environmental History of the last Millennia

Deicke, Matthias 05 November 2003 (has links)
No description available.
25

Redução do Acefato utilizando lacases produzidas por Trametes villosa e Pycnoporus sanguineus com Trichodermas isolados do Cerrado / Reduction of the laccases produced by using acephate Trametes villosa and Pycnoporus sanguineus Trichoderma with isolated from Savanna

SILVA, Carolina Braz 23 August 2011 (has links)
Made available in DSpace on 2014-07-29T15:01:45Z (GMT). No. of bitstreams: 1 Carolina Braz Silva.pdf: 810800 bytes, checksum: 70f05bacdef63b8aef2325761ace6cca (MD5) Previous issue date: 2011-08-23 / The organophosphate insecticides have been widely used for agricultural purposes. In the environment, organophosphates have been found in various environmental matrices, resulting in a growing environmental concern, among these compounds stands out Acephate, organophosphate and was registered by ANVISA reassessed in 2009, due to their toxicological and carcinogenic potential. The development of this work sought to select strains of Trichoderma harzianum capable of stimulating enzyme production by Trametes villosa and Pycnoporus sanguineus to promote the reduction of toxicity of Acephate. First there was the selection of strains of T. harzianum then became mixed cropping of selected strains of T. harzianum with Trametes villosa and T. harzianum with Pycnoporus sanguineus to determine the potential production of enzymes, and further tests were carried out with concentrations of 10% and 50% Acephate then held the toxicity test to assess the reduction of toxicity of Acephate. The results obtained in the experiments show that linhanges T. harzianum are good producers of lignin peroxidase (45 U.mL-1) and manganese peroxidase (23 Uml-1), the strains of T. harzianum were able to increase the production of Laccase in culture with T. villosa (20.57 Uml-1) and assessed that the fungi produced more enzymes in the presence of 50% Acephate. In toxicity tests, the samples with 10% Acephate addressed by the fungi indicated that compared to control, the association of P. sanguineus and Trichoderma T47 increased by 94% of cholinesterase, indicating a decrease in its toxicity, the association of P. sanguineus and Trichoderma harzianum ALL42 increase of 93% and the association between T. villosa and T. harzianum T39, an increase of 100% of cholinesterase, indicating that fungi were able to reduce the toxicity of Acephate. / Os inseticidas organofosforados têm sido amplamente utilizados para fins agrícolas. No ambiente, os organofosforados têm sido encontrados em diversas matrizes ambientais, resultando em uma crescente preocupação ambiental, dentre estes compostos destaca-se o Acefato, organofosforado que teve seu registro reavaliado pela ANVISA em 2009, devido ao seu potencial toxicológico e carcinogênico. O desenvolvimento deste trabalho buscou selecionar linhagens de Trichoderma harzianum capazes de estimular a produção enzimática por Trametes villosa e Pycnoporus sanguineus a fim de promover a diminuição da toxicidade do Acefato. Primeiramente realizou-se a seleção das linhagens de T. harzianum, em seguida fez-se o cultivo misto das linhagens selecionadas de T. harzianum com Trametes villosa e T. harzianum com Pycnoporus sanguineus para verificar o potencial de produção das enzimas, e posteriormente foram realizados os ensaios com concentrações de 10% e 50% de Acefato, em seguida realizou-se os teste de toxicidade para avaliar a redução da toxicidade do Acefato. Os resultados obtidos nos experimentos demonstram que as linhanges de T. harzianum são bons produtores de Lignina peroxidase (45 U.mL-1) e Manganês peroxidase (23 UmL-1), as linhagens de T. harzianum foram capazes de aumentar a produção de Lacase no cultivo com T. villosa (20,57 UmL-1) e que os fungos avaliados produziram mais enzimas na presença de 50% de Acefato. Nos testes de toxicidade, as amostras com 10% de Acefato tratadas pelos fungos indicaram que em relação ao controle, a associação de P. sanguineus e o Trichoderma T47 teve aumento de 94% de Colinesterase, indicando diminuição de sua toxicidade, na associação de P. sanguineus e Trichoderma harzianum ALL42 aumento de 93% e na associação entre T. villosa e o T. harzianum T39, aumento de 100% de Colinesterase, indicando que os fungos foram capazes de reduzir a toxicidade do Acefato.
26

Modified Phenol-Formaldehyde Resins for C-Fiber Reinforced Composites: Chemical Characteristics of Resins, Microstructure and Mechanical Properties of their Composites

Kim, Young Eun 06 January 2011 (has links)
This work correlates the chemistry of phenol-formaldehyde (PF) resins, its functionalities with their microstructural and mechanical properties in composite materials. The main focus is put on the development of the pores in dependence on the chemical composition of the resins and their influence on the structure of the material. Chemical characteristics of the synthesized resins are analyzed and physical/mechanical properties of the matrices based on PF resins are determined. Differences in the chemical properties are detected e.g. by FT-IR and NMR spectroscopy. They indicate the existence of similar molecular basic structure units, but different network conditions of the resins. DSC investigations point on different reaction mechanisms and temperatures; they reveal also their changed thermal behavior. The bulk matrix behavior differs from that of the composite based on the same resin due to the three dimensional stress and strain fields in the composites. The structure of the CFRP composites is strongly depended on the fiber/matrix interaction. The fiber matrix bonding (FMB) strength controls the load transfer via shear forces and therefore the segmentation of the fiber bundles.:1 Introduction 2 Theoretical Overview 2.1 Phenol-Formaldehyde Resins 2.1.1 Overview 2.1.2 Reactions of phenol-formaldehyde resin 2.1.2.1 Addition reaction 2.1.2.2 Condensation reaction 2.1.2.3 Curing 2.1.3 Application of phenol-formaldehyde resin 2.2 Carbon-Fiber 2.2.1 PAN type carbon fiber 2.2.2 Pitch type carbon fiber 2.2.3 Application of carbon fiber 2.3 Composites 2.3.1 Carbon fiber composites 2.3.2 Matrix 2.3.3. Interfaces 2.3.3.1 Carbon fiber side interface between carbon fiber and matrix 2.3.3.2 Matrix side interface between carbon fiber and matrix 2.3.3.3 Toughening of fiber-reinforced polymer 3 Goal and Works 3.1 Problem and Motivation 3.2 Objective and Works plan 4 Experiments and Methods 4.1 Materials 4.1.1 Chemical reagents 4.1.2 Carbon fiber weave 4.2 Synthesis of Resin 4.3 Fabrication of Matrix 4.4. Measurement methods and Experimental approach 4.4.1 Chemical analysis 4.4.2 Microstructure characterization 4.4.3 Mechanical test 5 Chemical characterization of modified phenol-formaldehyde resin 5.1 Fourier Transformed Infrared spectroscopy (FT-IR) 5.1.1 Introduction 5.1.2 Preparation and Measurement 5.1.3 Results and Discussion 5.2 Nuclear Magnetic Resonance spectroscopy (NMR) 5.2.1 Liquid 13C Nuclear Magnetic Resonance spectroscopy 5.2.1.1 Introduction 5.2.1.2 Preparation and Measurement 5.2.1.3 Results and Discussion 5.2.2 Solid 13C CP-MAS Nuclear Magnetic Resonance spectroscopy 5.2.2.1 Introduction 5.2.2.2 Preparation and Measurement 5.2.2.3 Results and Discussion 5.3 Simultaneous Thermal Analysis (STA) 5.3.1 Introduction 5.3.2 Preparation and Measurement 5.3.3 Results and Discussion 5.3.3.1 Simultaneous Thermal Analysis 5.3.3.2 Different Scanning Calorimetry 5.4 Conclusion 6 Microstructural Characterization 6.1 Porosity 6.1.1 Introduction 6.1.2 Preparation and Measurement 6.1.3 Results and Discussion 6.1.3.1 Density 6.1.3.2 Porosity 6.2 Morphology 6.2.1 Introduction 6.2.2 Preparation and Measurement 6.2.3 Results and Discussion 6.2.3.1 Optical Microscopy 6.3.3.2 Scanning Electron Microscopy 6.3.3.2.1 Observation of the bulk matrix 6.2.3.2.2 Structural observation of the composite 6.3 Conclusion 7 Mechanical Properties 7.1 Hardness test 7.1.1 Introduction 7.1.2 Preparation and Measurement 7.1.3 Results and Discussion 7.2 Micro-bending test 7.2.1 Introduction 7.2.2 Preparation and Measurement 7.2.3 Results and Discussion 7.3 Conclusion 8 Summary and Conclusion 8.1 Summary 8.2 Conclusion 9 References
27

Entwicklung eines naturnahen Bindemittels aus nachwachsenden Rohstoffen auf Proteinbasis zur Herstellung von Mitteldichten Faserplatten / Development of a near-natural protein based bonding agent for the production of medium density fibreboards

Schöpper, Christian 15 March 2006 (has links)
No description available.
28

Parametric study of tensile response of TRC specimens reinforced with epoxy-penetrated multi-filament yarns

Chudoba, Rostislav, Konrad, Martin, Schleser, Markus, Meskouris, Konstantin, Reisgen, Uwe 03 June 2009 (has links) (PDF)
The paper presents a meso-scopic modeling framework for the simulation of three-phase composite consisting of a brittle cementitious matrix and reinforcing AR-glass yarns impregnated with epoxy resin. The construction of the model is closely related to the experimental program covering both the meso-scale test (yarn tensile test and double sided pull-out test) and the macro-scale test in the form of tensile test on the textile reinforced concrete specimen. The predictions obtained using the model are validated using a-posteriori performed experiments.
29

Stickstoffhaltige Monomere zur Herstellung von Hybridmaterialien

Kaßner, Lysann 24 June 2015 (has links) (PDF)
In der vorliegenden Arbeit wurden stickstoffhaltige Monomere ausgehend von aromatischen Aminen oder Lactamen durch Umsetzung mit Chlorsilanen synthetisiert. Die so erhaltenen Derivate wurden mit Hilfe spektroskopischer und thermischer Analysenmethoden umfassend charakterisiert. Auf Basis der stickstoffhaltigen Monomere wurden über unterschiedliche Synthesestrategien organisch-anorganische, nanostrukturierte Hybridmaterialien hergestellt. Durch die thermisch induzierte Zwillingspolymerisation der Monomere 2,2‘-Spirobi[3,4-dihydro-1H-1,3,2-benzodiazasilin] und 1,1’,4,4‘-Tetrahydro-2,2‘-spirobi[benzo[d][1,3,2]-oxazasilin] gelang es, Hybridmaterialien bestehend aus Polyanilin-Formaldehyd-Harzen und Polysilazanen bzw. Siliciumdioxid unter Variation der Reaktionstemperatur herzustellen. Die Untersuchung der entstandenen Materialien erfolgte mittels spektroskopischer Methoden. Die Lactam-Monomere wurden durch die Zugabe von Aminocarbonsäuren zu Polyamid 6/SiO2- bzw. Polysiloxan-Kompositen umgesetzt. Hier stand die Ermittlung der molekularen Struktur, wie auch die Bestimmung des thermischen Verhaltens und der Homogenität der Materialien im Vordergrund. Es konnte gezeigt werden, dass die Synthese der thermoplastischen Kompositmaterialien auch in vergrößertem Maßstab reproduzierbar ist und die Produkte zudem zu Folien extrudierbar sind. / In the present work nitrogen-containing monomers have been synthesized by reactions of silicon tetrachloride with amines or lactames and were characterized by different spectroscopic and thermal analysis methods. The twin monomers 2,2‘-spirobi[3,4-dihydro-1H-1,3,2-benzodiazasiline] and 1,1’,4,4‘-tetrahydro-2,2‘-spirobi[benzo[d][1,3,2]¬oxazasiline] can be converted to hybrid materials containing polyaniline-formaldehyde resins and polysilazane or SiO2 by thermal induced twin polymerization under variation of the reaction temperature. The obtained nano composites were investigated by spectroscopic methods and electron microscopy. The lactam containing monomers were polymerized to polyamide 6/SiO2-composites by addition of aminocarbonic acids and -caprolactam. The analysis of the molecular structure as well as the investigation of the thermal behavior and the homogeneity of materials was emphasized. It could be shown, that the synthesis can be performed reproducible. Furthermore, it is possible to extrude the thermoplastic composite materials to films.
30

Die Initialphase der Vegetationsentwicklung nach Windwurf in Buchen-Wäldern auf Zechstein- und Buntsandstein-Standorten des südwestlichen Harzvorlandes / The initial phase of plant succession in windthrown beech (Fagus sylvatica) forests on base-rich and acidic sites in the Harz mountain foothills of southern Lower Saxony, Germany

Kompa, Thomas 03 November 2004 (has links)
No description available.

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