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Block copolymers are commercially significant and fundamentally interesting class of polymeric materials. The ability to undergo interfacial thermodynamics-controlled microphase separation from a completely disordered state in the melt to a specifically defined ordered structure through self-organization makes the block copolymers based materials unique. Block copolymer are strongly replacing many of the commercially available polymers due to their unique microstructure and properties. The most practical interests of block copolymers lie in the area of thermoplastic elastomers (TPEs). The objective of the present thesis work is to developing novel roots for enhancing the physical and mechanical properties in block copolymer and multigraft copolymers. Initially the properties are tailored by controlling chemical architecture at synthesis level and by selective blending at production level. This gives an easy access for improvement of the material properties and this is one of my major tasks in the present research modules. Further the block copolymer based TPEs are cross-linked in presence of electron beam (EB) radiation for developing materials with superior properties. The electron beam radiation has the ability to alter material parameters at molecular level for enhancing the macroscopic properties. The desirable physical and chemical properties can be easily attained by varying the radiation beam parameters. In addition to that, controlling the material at nanometer scale is one of the greatest challenges for current nanocomposite research. In elastomeric materials it is very prominent to fill the rubber matrix with nano particles from carbon or silica by melt mixing technique for enhancing the material properties. Other than conventional melt mixing technique, sol–gel processing is also a versatile technique, which making it possible to produce a wide variety of materials and to provide existing materials with novel properties. A combination of in situ sol-gel reaction with electron beam cross-linking in TPEs from triblock copolymer has been demonstrated for the first time as one of the novel nanocomposite system in this work. The main advantage of this system lies in controlling the material behaviour by finely tuning the size of silica nano particle generated inside TPE during in situ sol-gel reaction. Finally, the various roots employed for enhancing the material behaviour in block copolymers in the above research module were secussfully employed on super elastic multigraft copolymers for improving their strength withour sacrificing the super elastic nature.

Die inhärenten elastomeren Eigenschaften von Gummiwerkstoffen sind im Vergleich zu Thermoplasten in vielen Spezialanwendungen vorteilhaft. Jedoch sind ihre schlechten Reibungs- und Verschleißeigenschaften ein wesentlicher Nachteil besonders bei tribologischen Anwendungen. In der vorliegenden Arbeit wurden Reibung, Verschleiß und mechanische Eigenschaften von Gummiwerkstoffen, die Polytetrafluorethylen(PFTE)-Pulver enthalten, untersucht. Hauptziel war dabei die Verbesserung der Reibungs- und Verschleißeigenschaften bei weiterer Erhöhung der mechanischen Eigenschaften der Elastomere. Es ist bekannt, dass sich Reibungs- und Verschleißeigenschaften gummiähnlicher Materialien in vielfältiger Weise von den Reibungseigenschaften der meisten anderen Festkörper unterscheiden. Die Gründe dafür sind das viskoelastische Verhalten und der sehr geringe elastische Modul von Gummi. Die Verwendung von mit Elektronen modifizierten PTFE-Pulvern in Ethylen-Propylen-Dien-Monomer (EPDM) Kautschuken führt zu einer signifikanten Reduzierung der Reibung, Erhöhung der Verschleißfestigkeit und gleichzeitig zu verbesserten mechanischen Eigenschaften in Folge einer speziellen chemischen Kopplung zwischen dem modifiziertem PTFE-Pulver und dem EPDM. Gummirezeptur, Vernetzungsmethode und die viskoelastischen Materialeigenschaften beeinflussen wesentlich die tribologischen und mechanischen Eigenschaften. Morphologie, Dispersion und die chemische Kopplung des PTFE-Pulvers haben einen signifikanten Einfluss auf die Reibungs- und Verschleißverhalten. Die viskoelastischen Materialeigenschaften, d.h. Härte, E-Modul und tan delta (Verlustfaktor) der Gummimischungen sind kritische Parameter und erfordern deshalb eine Optimierung. In dieser Arbeit wurden zwei Modellsysteme untersucht, die auf zwei unterschiedlichen Kautschuktypen basieren: a) Ethylen-Propylene-Diene-Monomer (EPDM) Kautschuk und b) Polychloropren Kautschuk (CR). The inherent elastomeric properties of rubber compounds in comparison to thermoplastics are advantageous in many special purpose applications. However, their characteristic poor friction and wear properties are of prime concern especially in tribological applications. In the present work, friction, wear and mechanical properties of rubber compounds based on PTFE powder have been investigated. The main aim was to improve the friction and wear properties while further enhancing the mechanical properties of rubber compounds. As known, friction and wear behaviour of rubber-like materials differ in many ways from the frictional properties of most other solids. The reason for this is the high viscoelasticity and very low elastic modulus of rubber. The use of electron-modified PTFE powder in EPDM results in significant improvement in reducing friction, enhancing wear resistance and simultaneously improving mechanical properties due to specific chemical coupling between modified PTFE powder and EPDM. The rubber formulation, crosslinking mode and bulk viscoelastic properties strongly influences friction, wear and mechanical properties. The morphology, dispersion, and specific chemical coupling of PTFE powder play a significant role on friction and wear behaviour. The bulk viscoelastic properties, i.e. hardness, modulus and tan delta (loss factor) of the compounds are critical parameters and therefore, requires optimization. In this work two model systems based on two different rubber matrixes i.e. Ethylene-Propylene-Diene-Monomer (EPDM) and Chloroprene (CR) rubber have been investigated.

In der Dissertation wurden Nanokomposite mit unterschiedlichen Kautschuken (HNBR, EPDM, MAH-g-EPDM) als Basismaterial sowie diversen modifizierten Schichtsilikaten als Füllstoff hergestellt und charakterisiert. Untersucht wurden die sich ausbildenden Strukturen bzw. die Morphologie (Aggregation, mögliche Orientierungen), die mechanischen Eigenschafte (Verstärkungswirkung) sowie die Füllstoff-Füllstoff-Wechselwirkungen und die Polymer-Füllstoff-Wechselwirkungen.

Ziel der vorliegenden Arbeit war es, die Zusammenhänge zwischen der molekularen Architektur, Morphologie und den mechanischen bzw. bruchmechanischen Eigenschaften in S-SB-S-Triblockcopolymeren und deren Blends und in PI-PS-Multipfropfcopolymeren herauszuarbeiten und damit einerseits einen Beitrag für das Verständnis der Struktur-Eigenschaftsbeziehungen in Block- und Pfropfcopolymeren zu leisten und andererseits Möglichkeiten zur Entwicklung neuer Materialien aufzuzeigen, welche besondere Eigenschaftskombinationen aufweisen und damit ein bedeutendes Interesse für industrielle Anwendungen hervorrufen. Für die Untersuchungen wurde dabei der PS-Außenblockanteil und das S/B-Verhältnis im SB-Mittelblock in S-SB-S-Triblockcopolymeren, die Thermoplast/Thermoplastisches Elastomer (TP/TPE) -Zusammensetzung in S-SB-S-Triblockcopolymer-Blends sowie die Funktionalität und die Anzahl der Verknüpfungspunkte in PI-PS-Multipfropfcopolymeren variiert. Zur Charakterisierung der Phasenmischbarkeit und der Morphologie wurden die dynamisch mechanische Analyse (DMA), die Transmissionselektronenmikroskopie (TEM) und die Röntgenkleinwinkelstreuung (SAXS) angewandt. Die mechanischen Eigenschaften wurden mit dem einachsigen Zugversuch untersucht. Bruchmechanische Untersuchungen erfolgten unter Anwendung der „Essential Work of Fracture“- (EWF-) Methode, welche als Konzept der „Post-Yield“-Bruchmechanik innerhalb der Fließbruchmechanik für duktile nanostrukturierte polymere Materialien sehr gut anwendbar ist und Aussagen zur Bruchzähigkeit der Materialien liefert. Zur näheren Charakterisierung des zeitaufgelösten Deformationsverhaltens sowie der Rissausbreitungskinetik wurden die Dehnungsfeldanalyse, eine Bruchflächenanalyse mittels Rasterelektronenmikroskopie (REM) sowie das Risswiderstandskurven-Konzept angewandt. Die Untersuchungen der S-SB-S-Triblockcopolymersysteme und der PI-PS-Multipfropfcopolymere konnten den signifikanten Einfluss der molekularen Architektur, der Blockzusammensetzung und des PS-Gehaltes auf das Phasenverhalten, die Morphologie und die Eigenschaften klar herausstellen. Durch die Variation dieser Parameter kann das Eigenschaftsspektrum von thermoplastisch zu elastomer eingestellt und somit sowohl TPs oder TPEs mit hoher Steifigkeit und Zähigkeit als auch TPEs mit superelastischem Charakter erzeugt werden. Daraus eröffnet sich ein breiter Anwendungsbereich dieser Materialien, welche aufgrund ihrer Transparenz und physiologischen Verträglichkeit auch interessante optische und gesundheitliche Vorteile mitbringen. Es konnte gezeigt werden, dass durch die systematische Variation der Architektur die gezielte Einstellung gewünschter Eigenschaftsprofile möglich ist. Die Arbeit leistet somit einen Beitrag zur Entwicklung anwendungsorientierter Materialkonzepte, welche ingenieurwissenschaftlich interessant sind. The aim of this thesis was to study the relation between molecular architecture, morphology and (fracture) mechanical properties of S-SB-S triblock copolymers and PI-PS multigraft copolymers. Hence, this work should contribute to the understanding of structure-property-relationship in block and multigraft copolymers and thus offer possibilities for the development of novel materials with special properties interesting for industrial application. Within this study in the case of S-SB-S triblock copolymers the PS outer block content and the S/B ratio of the middle block, in the case of S-SB-S triblock copolymer blends the thermoplast/thermoplastic elastomer (TP/TPE) composition and in case of PI-PS multigraft copolymers the functionality and number of branch points were varied. For the characterisation of morphology and phase miscibility dynamic mechanical analysis (DMA), transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) were applied. Uniaxial tensile tests were carried out to investigate the mechanical properties. The fracture mechanical behaviour was studied using essential work of fracture (EWF) concept based on the post yield fracture mechanic principles, which is suitable to characterise fracture toughness of ductile nanostructured materials. The time resolved analysis of deformation and fracture behaviour was characterised qualitatively by strain field analysis, scanning electron microscopy (SEM) of the fractured surfaces and quantitatively by evaluation of the crack propagation kinetics and construction of R-curves. This study clearly highlights the significant influence of molecular architecture block composition and PS content on the phase behaviour, morphology and properties of S-SB-S triblock copolymers and PI-PS multigraft copolymers. By varying these parameters the property profile can be adjusted diversifying from thermoplastic to elastomeric and both TP or TPE materials with high stiffness and toughness and TPEs with super-elastic characteristics can be designed. Hence, fundamentally it offers a broad scope of application of these materials, in which physiological compatibility and transparency are added advantages. Thus, conceptually it could be shown, that by systematic variation of the architecture desired property profiles can be adjusted. Therefore the present work contributes to the development of application-oriented material concepts, which are interesting in engineering terms.

The presented research report deals with the investigation of magnesium aluminum based layered double hydroxide (LDH) as a potential nanofiller and flame-retardant for polymers with special reference to polyethylene. LDH is a mixed hydroxide of di- and trivalent metal ions that crystallizes in the form of mineral brucite. The basic reason for selecting LDH or more specifically magnesium-aluminum based LDH (Mg-Al LDH) is their typical metal hydroxide-like chemistry and conventional clay-like layered crystalline structure. The former is helpful in the direct participation in flame inhibition through endothermic decomposition and stable char formation. On the other hand, the later makes LDH suitable for polymer nanocomposite preparation, which can address the poor dispersibility problem associated with conventional metal hydroxide type fillers in polyolefin matrix. Besides, unlike layered silicate type clays (often reported for their capability to improve flame retardancy of polymers), LDH being reactive during combustion has higher efficiency to reduce the heat released during combustion of the composites. LDH clay with fixed Al:Mg ratio was synthesized using urea hydrolysis method and characterized. The organic modification of Mg-Al LDH using anionic surfactants has been studied in details. The main purpose of such modification is to enlarge the interlayer distance and to render it more organophilic. The surfactants were selected based on their functionality, chain length, etc and the modification was carried out by regeneration method. In the modified LDHs, the surfactants anions are arranged as a monolayer in the interlayer region and expand the interlayer distance according to their tail size. PE/LDH nanocomposites were prepared by melt-compounding method using a co-rotating tightly intermeshed twin-screw extruder and the morphological, mechanical and flammability properties of the nanocomposites were investigated in details. The X-ray diffraction analysis and electron microscopic analysis show a complex LDH particle morphology with hierarchy of particle size and shape starting from exfoliated particles fragments to particle aggregates over few hundred nm size. The exfoliated LDH platelets are distributed both in the vicinity of large particles and also in the bulk matrix. The melt rheological characterization of the nanocomposites also reflects the similar complex particle morphology. The dynamic oscillatory shear experiments showed that with increasing LDH concentration, the rheological behavior of the nanocomposite melts deviates strongly from that of the unfilled polyethylene. Thermogravimetric analysis (TGA) shows that LDH significantly improves the thermal stability of the polymer matrix in comparison to the unfilled polymer. The flammability studies of the PE/LDH nanocomposites have been reported in terms of various standard methods, like limited oxygen index (LOI), cone-calorimetry and UL-94 vertical and horizontal burn tests. The cone-calorimetric investigation shows that the nanocomposites have significantly lower burning rate and heat released during combustion. With increasing concentration of LDH though the LOI value of the nanocomposite increases marginally, the burning behavior, like dripping, rate of burning, etc are significantly improved. The flammability performance of LDH in combination with other commonly used flame-retardant (magnesium hydroxide) was also investigated. It has been observed that in polyethylene, a 50 wt% combination filler (4:1 weight ratio of magnesium hydroxide and LDH) can provide similar flammability ratings (like V0 rating in UL94 test, no dripping, etc) as that observed with 60 wt% magnesium hydroxide alone.

Mit der Entwicklung und Einführung ökologischer Bauweise im Neubau sowie neuen Baustoffsystemen in Sandwichbauweise wird es zunehmend erforderlich, neue effektive Befestigungsvarianten zu entwickeln, die eine dauerhafte Fixierung auch unter sicherheitstechnischen Bestimmungen sowie aus Garantie- bzw. haftungsrechtlichen Gründen ermöglichen. Die aus der Praxis bisher bekannten chemischen Befestigungssysteme (Zweikomponentenverbundmörtel, Verbundankerpatronen) weisen hinsichtlich der Applikation unter bautechnischen Bedingungen noch einige Nachteile auf. Dazu gehören vor allem längere Aushärtungszeiten zur Realisierung der abschließenden Verbundfestigkeit, Inhomogenitäten im Verbund, der Einsatz toxischer Verbindungen und eine Limitierung der Applikationsmöglichkeiten in horizontalen und Überkopf-Einsatzbereichen sowie Hohlkammersystemen. Alle zuvor genannten Punkte haben bis jetzt die Nutzung solcher Verbundwerkstoffe als universale Anwendungsmöglichkeit verhindert. Ein neues chemisches Befestigungssystem, welches aus Novolak gehärteten mit Hexamethylentetramin (Hexa) und anorganischen Füllstoff besteht, wurde für Applikationen in Beton entwickelt. Das Bindemittel härtet bei der Temperaturzuführung aus. Die unkatalysierte Befestigungsmasse zeigt bei einer Temperatur zwischen 150-300 °C eine hohe Reaktivität. Die Vorteile dieses Systems sind die unbegrenzte Lagerfähigkeit der vorgemischten härtbaren Masse sowie die Gewährleistung einer homogenen Netzwerkstruktur im gesamten Verbund und sie ist frei von giftigen und flüchtigen Substanzen. Auf den Einsatz toxischer Substanzen wurde verzichtet. In dieser Arbeit wurde die Gesamtkinetik der Reaktion während des Aushärtungsprozesses dieser Polymerkomposite untersucht. Die DSC- (nicht-isothermen, isothermen) und MDSC-Untersuchungen haben sich als ein sicheres Verfahren zur Qualitätskontrolle des Aushärtezustands der Befestigungssysteme herausgestellt. Parallel zur nicht-isothermischen und isothermischen DSC wurden Leitfähigkeitsmessungen durchgeführt, um den Endpunkt der Aushärtungsreaktion zu bestimmen. The development and introduction of ecological construction methods and the use of sandwich materials make it necessary to develop new fixing systems and technologies. Dealing with the application in concrete and other substrates commercial chemical fixing systems show some disadvantages up to date. Especially the rather long curing time in order to realize the final bond strength, inhomogenities in the composite, the partial use of toxic substances and application limits of such systems in horizontal direction as well as hollow section materials has so far prevented the use of such composites for all-purpose applications. A new chemical fixing system, which consists of hexamethylene tetramine (hexa) cured novolac and inorganic filler, was developed for application in concrete. It is applied by a thermo-curing procedure. The uncatalyzed curable mixture has a high reactivity at temperature between 150-300 °C. Compared with commercial chemical fixing systems, the premixed curable mass has many benefits. First it has a unique storage stability and second, it is free of toxic and volatile substances. Another important aspect is, it is self-foaming. In this study was investigated the overall kinetics of the reaction during the curing process of these polymer composites. An appropriate method for this experiment proved to be the DSC in isothermal and non-isothermal mode and MDSC. This turned out to be a safe quality control technique for these systems. Parallel to the non-isothermal and isothermal DSC conductivity measurements have been performed to determine the end point of the curing reaction.

The production of fine filaments using the melt spinning process needs considerable effort. A thermoplastic melt is stretched from the spinneret under a constant take-up speed. The high performance thermoplastic PEEK is solidified in the melt spinning process in a small distance and short time. Therefore, the fine PEEK filaments in the fibre formation zone underwent a high deformation and cooling rate. To make the melt spinning process stable and to produce the fine PEEK filaments, material properties and material behaviour are examined using on-line and off-line measurements. The fibre speed measured using Laser Doppler Anemometry and simultaneous temperature measured using infrared thermography enable both the strain rate and consequently the apparent extensional viscosity to be estimated. This provides the apparent extensional viscosity over the spinning line, which can itself show the structural development of PEEK fibres in the fibre formation zone, i.e. necking and solidification phenomena. The one-dimensional fibre formation model must include both procedural and material parameters. The heat transfer coefficient was estimated using the filament temperature measurement and showed a relatively high contribution of radiation and free convection in comparison to forced convection near the spinneret. The improved model of PEEK fibre formation gave a good agreement to both temperature and speed measurements, and also confirmed the high deformation rate effect on the extensional viscosity, which could be simulated with a properly generalised Newtonian constitutive equation. The end properties of the fibres, such as as-spun filament fineness, orientation (expressed using total birefringence) and total crystallisation (examined using DSC) are investigated in relation to different spinning conditions, i.e. take-up speed, throughput and the draw down ratio. The tensile test diagram results, measuring phenomena such as the elongation at break, tenacity, and the Young modulus of elasticity are also analysed in order to complete the correlation of the above-mentioned spinning conditions to the structural properties of as-spun fine PEEK filaments. The melt spinning of fine PEEK fibres under different spinning conditions is examined with the purpose of finding the optimum take-up speed and throughputs. Other spinning conditions, such as the temperature of melt processing, and the arrangement and diameter of the spinneret holes, are changed in order to make the process more stable. The recommendations for further study can be used to further examine some aspects of this work; however, this work presents a new concept for fine PEEK melt spinning supported by spinnability examinations under different spinning conditions and the improved model of fibre formation, which is also relevant for typical industrial processing applications.

Composite laminates are an important subject of modern technology and engineering. The most common mode of failure in these materials is probably interlaminar fracture (delamination). Delamination growth under applied fatigue loads usually leads to structural integrity loss of the composite laminate, and hence its catastrophic failure. It is known that several parameters can affect the fatigue fracture performance of laminates. These include the constituent material properties, composite geometry, fatigue load variables or environmental factors. The knowledge about effects of these parameters on fatigue delamination growth can lead to a better understanding of composite fatigue fracture behaviour. Effects of some of these parameters can be elucidated by undertaking appropriate sensitivity analysis combined with the finite element method (FEM) and related software. The purpose of this work was three-fold. The first goal was the elaboration and computational implementation of FEM-based numerical strategies for the sensitivity analysis of interface fatigue crack propagation in elastic composite laminates. The second goal of this work was the numerical determination and investigation of displacement and stress fields near the crack tip, contact pressures along crack surfaces, mixed mode angle, energy release rate and the number of cumulative fatigue cycles. The third aim of the present study was to use the developed strategies to evaluate numerically the sensitivity gradients of the total energy release rate and fatigue life with respect to design variables of the curved boron/epoxy-aluminium (B/Ep-Al) composite laminate in two different material configurations under cyclic shear of constant amplitude. This study provided novel strategies for undertaking sensitivity analysis of the delamination growth under fatigue loads for elastic composite laminates using the package ANSYS. The numerical results of the work shed more light on mechanisms of interfacial crack propagation under cyclic shear in the case of a curved B/Ep-Al composite laminate. Moreover, the outcome of the sensitivity gradients demonstrated some advantages for using the sensitivity analysis to pinpoint directions for the optimisation of fatigue fracture performance of elastic laminates. The strategies proposed in this work can be used to study the sensitivity of the interface fatigue crack propagation in other elastic laminates, if the crack propagates at the interface between the elastic and isotropic components. However, the strategies can be potentially extended to composites with interfacial cracks propagating between two non-isotropic constituents under a constant amplitude fatigue load. Finally, the strategies can also be used to undertake the sensitivity analysis of composite fatigue life with respect to variables of fatigue load.