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A key sector of the rubber processing industry deals with improving mixing processes in silica/silane technology and with the discontinuous batch production of the corresponding rubber compounds in the rubber internal mixer compounding process. To achieve the desired material properties in the respective end product, both producers of technical rubber products and tire makers are in need of a mixing process that is effective (in terms of both dispersion and distributive mixing efficiency). Major differences in polarity between nonpolar rubber and highly polar silica impede the incorporation and dispersion of silica, the active filler. This effect also influences the quality of distributive mixing of other compound ingredients and thus the compound homogeneity that is to be attained.Whereas the reflected-light microscopy method, with image processing, has been tested and fully developed for industrial grade use in analyzing filler particle macrodispersion, employment of Laser Induced Breakdown Spectroscopy (LIBS) remains relatively unknown in rubber processing as a means of analyzing distributive mixing efficiency via determination of the homogeneous distribution of a specific marker across a batch volume.The results of this research activity have shown that under atmospheric conditions (with no vacuum), LIBS is a suitable method for analyzing the distributive mixing quality of components within a rubber compound batch. The method can be applied both in compounds free of carbon black fillers and in those containing carbon black fillers. Thanks to its very short measurement time (here: approx. 40 s for analysis of a roughly postage-stamp-sized specimen surface), it yields a statistically representative statement as to the distributive quality of a marker (like zinc) in the used compound.

In this work, the continuous compounding process of silica-based rubber compounds with in-situ silanization was investigated in co-rotating twin screw extruders. In regards to achieving better silica dispersion and a high degree of silanization as well as the removal of the condensation products from the compounding process, the twin-screw extruder has great advantages as an alternative to the internal mixer for the preparation of silica compounds. For a simplified recipe, which contains only silica and no carbon black as filler, the question of the completeness of the silanization can be answered positively for the Ø 44 mm extruder. Time and temperature control are the crucial factors in the mixing process. The optimization process is strongly determined by trade-offs.In the continuous compounding with extruder cascades, complete silanization and good silica dispersion must be ensured. The sequence of compounding stages has a strong influence on the properties of the mixture. It is technologically important that the silanization reaction begins promptly at the start of the mixing process. A complete silanization is the prerequisite for a low viscosity of the silica compound and for the formation of a strong polymer-filler interaction. Shorter residence time, lower energy consumption and comparable mixture properties are the notable advantages of the compounding process in the twin screw extruder.In order to obtain a better understanding of the continuous compounding process, a simulation program, MOREX, is being employed parallel to the extrusion experiments. It can be shown that simulation calculation is very helpful in optimizing the screw configuration and reducing the experimental effort.

The first uniaxial extension of reinforced rubber materials causes stress softening (the Mullins effect) not only in this loading direction but in any other direction of subsequent extension. However, the Mullins effect is less pronounced after a change of loading direction than in the direction of the initial loading. Due to the deformation history mechanical behaviour of the the rubber vulcanisate is distinctly anisotropic. To trace the anisotropic Mullins effect, firstly the standard test method for characterization of the isotropic mechanical behaviour must be extended. The appropriate type of specimen enables to perform multiple load steps with alternating load directions. After repeated stretching in the same direction, a subsequent first uniaxial loading in any other direction is characterized by a stiffer stress–strain behavior compared with the stabilized curve of the previous primary load. Due to the high relevance of the primary permanent set for this experimental method and their strong influence on the secondary load step, the direction dependent consideration is studied. On behalf of a more comprehensive evaluation of the anisotropic Mullins effect the role of active filer like carbon black and silica was investigated. In particular, not only the influence of basic properties of carbon blacks, such as specific surface area or structure, but also the influence of the amount incorporated was determined experimentally. The comparison of carbon black and silica filled vulcanisates provided more insights in the anisotropic material behaviour of reinforced elastomers. For the anisotropic (primary) Mullins effect a similar behaviour can be detected regarding the well-known one-dimensional Mullins effect. In summary, the vulcanisates soften high levelly in the primary load (one-dimensional Mullins effect) and in this way, they show a high level deformation induced anisotropy of the Mullins effect. For the visualization of the direction-dependent stress softening the comparison of the Mullins effect and the applied primary strain energy density is proposed to identify the resulting anisotropic material properties of the elastomer.

The material class of biopolymers attracts increasing attention and is considered as a promising development in the plastics industry. In particular, the degradable polymers play an important role due to their environmentally friendly properties and the wide range of applications for which they can be deployed for. These range from biodegradable packaging to biomedical devices. Polyesteramides belong to the class of biopolymers and combine the different properties of amides and esters. The ester and amide amount in the polyesteramides as well as their properties can be influenced and controlled chemically during their synthesis. Especially for biomedical applications polyesteramides are considered to be an important material. As they are surface eroding polymers, they are not causing a local in vivo acidity during their degradation and hence are, compared to other polymers which are used for such devices, avoiding inflammatory responses of the body. In this work the synthesis of a polyesteramides with good thermal, mechanical and processing properties, by using reactive extrusion, is being developed. The focus thereby lies on the synthesis of thermoplastic polyesteramides. These are mainly produced by batch synthesis and could not achieve an importance on the market up to now. In literature examples for the preparation of polyesteramides on a twin-screw extruder using the monomers epsilon-caprolactam and epsilon-caprolactone were reported, but this process has not achieved any industrial relevance so far. In this work a new synthesis approach for the continuous synthesis of polyesteramides is presented, which is based on the anionic ring opening polymerization of epsilon-caprolactam in the melt of commercially available polyester-polycaprolactone. The amide fragments are incorporated into the polyester via a chain transfer reaction during polymerization, which leads to polyesteramides with blocky nature. As the melt viscosity before and after the polymerization reaction, is comparable, the process design can easily be simplified, which allows an easier scale-up. The first part of this work is focused on the chemical development of the reaction and its evaluation. Furthermore, the requirements for the synthesis on a twin-screw extruder as well as the required properties of the extrudate and the polymer for such a processing are defined. To assess and optimize the synthesis the reaction was performed on a twin-screw microcompounder in batches. The influence of the chemicals and how to conduct the process, especially regarding temperature and reaction progress are studied. The characterization of the resulting polymers allowed their subsequent evaluation, and thus the assessment and evaluation of the chemical reaction and the process. At reaction temperatures of 180 °C and residence times of ten minutes polyesteramides with blocky structure were synthesized at high conversion rates. For one of the studied mixtures the synthesis was carried out continuously on a laboratory extruder with a screw diameter of 16 mm and a L/D=25. The focus lay on the development of the process control as well as the screw design. Calculations to determine the residence time of the polymer using a simulation program were performed in order to avoid time-consuming experiments with „trial-and-error“ principle. After optimization and configuration of the screw it was possible to transfer the synthesis of the mixture synthesized in the microcompounder to a laboratory extruder process resulting in comparable analytical results. The work contributes to the continuous synthesis of polyesteramides by reactive extrusion. Furthermore it points out that the material class of biopolymers and in particular of polyesteramides still offers a great research potential.

The development of thermal joining process for plastics-metal components without filler material, into a hybrid component is a goal of the workgroup "Thermal Joining" in the Cluster of Excellence "Integrative Production Technology for High-wage Countries." In order to develop thermal joining processes, basic knowledge needs to be created. To gain this knowledge a simple machine is created which allows to bond plastic to metal, in a lap joint or butt joint, to a hybrid product. The plastic is locally plasticized and under welding pressure applied on the metal surface. The heat required to plasticize is introduced via heat conduction into the metal. Accompanying to the joining experiments the process is mapped in a simulation. The simulation based imaging of temperature gradients across the thickness of the plastic and the metal part gives valuable insights into details of the thermal joining process.The relative error in the simulation was 1.25%. In addition to the material combinations, classic joining parameters, such as joining temperature, joining pressure or joining time are varied. Different metals such as stainless steel, aluminum and galvanized steel are combined with different thermoplastics like polycarbonate, polyamide and polybutyleneterephthalate. The latter two thermoplastics are also modified with glassfiber. The surface properties of metals have a significant influence on the adhesion quality. To investigate this influence the roughness of the metal surface is modified by sand blasting or it will be provided with undercuts by laser structuring. With optimal choice of parameters a cohesive failure of the plastic partner is possible. The bond strength is determined in tensile tests. Tensile stress at break can be up to 35 MPa.

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.

The mixing behaviour of new material systems (PES/glass- and PP/metal-blends) is studied in dependence of the process parameters screw-speed, material type and non-polymer rate in the present dissertation. The glass and the metal are low melting materials and they are processed in a fluid state. The work is focused on a small mixing zone, consisting of two kneading elements in a co-rotating twin screw extruder. It is shown by the analysis that the correlations between process parameters and development of morphology parameters (particle diameter, number of particles) in the mixing zone could be provided evidently. The correlations are described by twenty-five models, which have medium up to high coefficients of determination. Furthermore the fluid flow in the mixing zone is studied by three-dimensional FEA-simulations. The influence of a process parameter change on fluid-mechanical parameters (e.g. residence time, rate of deformation) is analysed. A change of the screw speed shows a highly influence on the parameters, while a variation of material density and flow rate has no significant effect on the fluid-mechanical parameters. A method for the development of regression models is developed by combination of mathematical analysis (correlation, regression and variance) in the present work. The functional correlations between fluid-mechanical parameters and the change of morphology parameters in the mixing zone are determined by this method. The models are tested on their reliability and also they could be rated by the method. Therefore the criteria accuracy, simpleness and plausibility are applied. The method is used to determine the correlations between fluid-mechanical parameters and morphology parameters. It shows that the parameters particle diameter, standard deviation of the diameter distribution and number of particles before the mixing zone, disperse phase ratio, viscosity ratio, collision frequency and capillary number are adequate for the description of the morphology change. The generalisation of the parameter effects on the processes dispersion and coalescence is attempted. The parameters residence time, mixing index and entropy proved to be not adequate for the description of morphology change. The application of the parameter rate of deformation is problematic, because the number of dispersion and coalescence processes increase with an increasing rate of deformation. The differences between the processing behaviour of PES/glass- and PP/metal-blends are causally determined by the difference of the particle diameters before the mixing zone and the different viscosity ratios of the blends. Furthermore a new visualisation method for simulation data of flow- and mixing-processes in the extruder is developed with the assistance of Virtual Reality (VR) techniques. Thereby the Virtual Reality techniques are utilised for an analysis of the compounding processes in plastics processing.

In der Arbeit werden die Möglichkeiten der Abschirmung elektromagnetischer Wellen durch spritzgegossene Kunststoffgehäuse aus stahlfasergefüllten Thermoplasten untersucht. Beginnend mit einer Erläuterung der Abschirmprinzipien, werden die verschiedenen Verfahren zur Schirmdämpfung erläutert und ein Überblick der elektrisch leitfähigen Kunststoffcompounds gegeben. Weiterhin werden Verfahren zur Messung der Schirmdämpfung und Leitfähigkeit vorgestellt. Der experimentelle Teil befasst sich mit der Charakterisierung der Materialeigenschaften. Es wird der Einfluss von Faserfüllgrad und -länge experimentell untersucht und mit Modellansätzen zur Beschreibung der Schirmdämpfung und Leitfähigkeit verglichen. Die Untersuchung des Verarbeitungsverhaltens beim Spritzgießen beinhaltet die Beschreibung des rheologischen Verhaltens stahlfasergefüllter Thermoplaste sowie die Auswirkungen der Prozessbedingungen und der Bindenahtbildung auf die Schirmwirkung. Ausführungen zum konstruktiven Einfluss auf die Schirmdämpfung unter Betrachtung der Gestaltungsmöglichkeiten der Gehäuseverbindung und möglicher Aperturen schließen die Arbeiten ab.

The latest legal requirements call to an increasing degree of purification for plastics, for both virgin and recycled material. Abidance by the law demands new processing technologies for purifying plastics. The extraction with supercritical carbon dioxide could be an approach. Supercritical carbon dioxide is characterized by a high diffusion coefficient, a low viscosity and a high density. These properties are determining the outstanding solubility in scCO2 even for higher molecular substances. Furthermore CO2 is non flammable, ecologically safe, inexpensive and non toxic. One disadvantage of CO2 is its low polarity and thus its low solubility for polar substances. The polarity of the extracting agent can be influenced specifically by dosing additional cosolvents like methanol in scCO2. Carbon dioxide also is a gas which causes the greenhouse effect and should therefore be recycled. The usage of scCO2 as an extracting agent in a twin screw extruder offers high potential for decreasing the amount of contaminations in the polymer melt. The extraction process is examined in the present paper for cleaning polymer melts. Main objective of the extraction is to remove foreign substances as monomers, solvent residues, processing aids and contaminations, which are diffusing into the interior material by using the plastics. These contaminations are dispersed or dissolved in the polymer. The applicability of a twin screw extruder for purifying polymer melt is analysed for both virgin material (two types of polyamide 12) to remove monomers and specifically contaminated high density polyethylene. To implement the extraction process on a twin screw extruder the compounding process has to be modified regarding this process technology, in order to keep the CO2 in its overcritical state at high pressures > 75 bar. This is an additional requirement for common twin screw extruders. Pressure tightness was achieved by using a copper sealing in combination with a sealing paste. For dimensioning the extruder for extraction purposes, the processing unit should feature few linkage points. Besides the pressure tightness of the extruder the screw configuration has to be determined and optimised. A reflow zone following the zone for the CO2-outlet is proved to provide the possibility for the carbon dioxide, which is swept away with the polymer, to flow against the polymer flow back to the CO2 outlet. After elaborating a sufficient process for taking samples, dependences of different processing parameters the extraction effect were researched. In general the highest extraction effect can be realised by increasing pressure, screw speed, processing temperature and the CO2-flow. Contrary to this an increased temperature level results in charred melt and a high CO2 flow has a negative effect on the economy of the extraction process. The integration of a degassing unit and a counter flow process were also investigated. To do so an extruder cascade is inevitable due to safety reasons. Furthermore the extruder cascade facilitates stable processing conditions and simplified process control. Regarding the counter flow processing, the used screw configuration is inappropriate. Due to this improvement of the screw design is inevitable. Industry is reluctant using supercritical fluids despite of the considerable advantages. Reasons for the scepticism can be found in the high investment cost al well as using hegh pressure processing technology. However the increasing relevance of legal requirements and the progressive development will promote this technology.

Laser transmission beam welding is only possible, if one joining part is transparent for the laser beam. The other part is non-transparent and thus absorbs the light. Within the absorbing part light energy is altered into heat energy. In order to start the welding process, both parts have to be in contact with each other. As a general finding of this research, the welding process itself can be divided into three different phases. During the transmission of the laser beam through the transparent part the polymer scatters the laser beam and also absorbs a small amount of the laser light. Thermographic evaluations are able to show the amount of scattering. In the experiments laser beam transparent parts were heated up locally and the temperature image of the front and the rear side of the sample were evaluated. Calculations, done before the welding process, are a method to predict the welding temperature. A comparison between calculated and actual temperatures show that there is a difference between the two temperature curves. Thus, it is not possible to exactly pre-calculate the temperature curves of the process. The surface structure of the welding parts significantly influences the welding process. As a result, different surface roughness generally leads to reduced tractive force, when compared to polished surfaces. Additionally, welding is only possible with the right geometry of the component parts, which means these parts have to be specially designed. Photoelasticity and transmission detection with an infrared beam can be used for non-destructive welding line tests. The photoelasticity test revealed the additional presence of isochromates directly beneath the welding line of a transparent PC sample. Former research has not been able to provide a method to investigate the welding line of two laser transmission beam welded black parts. This problem has successfully been solved by using an infrared light emitting and detecting camera.

Within the finite element analysis (FEA) so-called material models are used for the simulation of the mechanical behavior of rubber materials. These material models have to be calibrated with experimentally determined data before a FEA-simulation can be started. A new concept is developed, which reduces the experimental expenditure using the application of time/temperature shifts (TTS) and amplitude/temperature shifts (ATS). In order to describe the time/temperature and amplitude/temperature dependent material behavior up to high deformations, an emphasis of the investigations is on the description of the temperature dependency of strain crystallization processes. Additionally a concept is developed, which also permits a consideration of strain softening effects with material models used in today's FEA programs. An emphasis of these investigations is the question, which amounts of stress correspond for the different states of deformation.

There is a growing need for precision rubber parts and complex rubber components for the automotive sector. The quality requirements rising thereby lead to the increasing meaning of the quality assurance and the quality management in the rubber industry. In the rubber processing, there is an extra step or processing phase the material compounding step, which does not exist in the processing of plastics. This additional discontinual processing step may account for the higher risk for deviation between rubber batches or within a batch. This in turn may lead to problems in the subsequent stages and result in deviations in the final product properties. This thesis propounds guidelines and methods for efficient process analysis and optimization with particular focus on the rubber mixing process in an internal mixer. The research methods used for this thesis were process analyses and modeling which allowed the exact determination of correlation between the mixing process and the rest of the process chain. The experiments carried out focused on selected steps of the production of the rubber parts on mixing process in the rubber internal mixer, transfer molding process an on the injection molding process. In the rubber industry, there are many different testing approaches used and their validity is not always sufficient. At the same time they are inappropriate. Consequently the rubber characterization methods were analyzed. The focal point of the investigations was to find out the method most correlated to the rubber behavior of the rubber compound during processing and to the properties of the final product. As an approach to this problem statistical methods of the process analysis, like correlation analysis or regression were used. The validity of the rubber compound testing methods was determinated by correlational coefficient and the coefficient of certainty. The results showed that there is a direct correlation between the viscose and elastic compound properties and the qualities of the final product. In additional to that the rheological properties of the rubber mixture gives valuable information about the processing behavior in an injection molding machine and mold. The investigations were carried out using various measuring methods such as Rubber Process Analyzer (RPA), High Pressure Rheometer, Rheovulkameter, Mooney Viscometer. The RPA and the Mooney-Viscometer measurements proved to be the most accurately (reliable) of the method used. This thesis also covers the development and application of mathematical models for online-prediction of the compound properties during the mixing process in an internal mixer using Artificial Neural Networks (ANN) and linear regression analysis. These methods were used to predict the different rubber compound properties based on different types of rubber and on different fillers (carbon blacks and silica). Using the regression models in most cases it was possible to describe the interrelationship with a very high level of certainty. The advantages of using models based on ANN were evident when dealing with non linear interrelationships, e.g. (for silica-compound) In this case it was possible to achieve coefficients of certainty of about 90%. It was possible to prove the practical relevance of this modeling method for a tire compound produced in a 320 liters production internal rubber mixer. In this case it was possible to calculate the compound property – Mooney-viscosity with a high degree of certainty using ANN. Based on the results, an online prediction system was developed, presented and explored in this thesis. This system can be used in practice to reduce the number of compound tests carried out for quality control in the rubber industry.

More and more micro technology attaches importance in plastics processing. This document represents fundamental investigations of plastics laser welding in micro technology. Requirements of such a laser welding process are for example welding accuracy of nearly one micron or minimisation of lateral polymer melt flow at the welding area into the weld bead. These questions are investigated by laser transmissions welding.

This thesis focuses on the influence of the material rheology on the quality and the prediction and optimisation of the wall thickness distribution of thermoformed parts. In particular, the technique of the Membrane-Inflation Rheometer was improved. In this rheological test thermoplastic samples are deformed in an equibiaxial strain mode under process relevant conditions for temperature and strain rate. The rheological properties of thermoforming sheets were correlated with the quality of thermoformed parts. The rheological data was additionally used to calibrate a viscoelastic material model. The material constants are used as input for Finite-Element-Analysis of the deformation step in the thermoforming process. Based on the simulation of deformation in the thermoforming process, an optimisation algorithm is presented, which is used to calculate the temperature distribution in the thermoforming sheet to obtain the most even final wall thickness distribution. For different thermoforming parts an improvement of the final wallt hickness distribution could be achieved.