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The mechanical properties of injection moulded plastic parts depend on the morphology, the degree of crystallinity and the molecular orientation of the formed microstructure. In order to take the variation of the microstructure into account in a structural analysis, a novel multi-scale, integrated simulation approach is presented here. At first, a coupled mould filling and heat transfer analysis is achieved at the macroscale and its temperature field is transferred to the micromodel. Based on the concept of cellular automata, a 3-D microstructure evolution model is developed. It specifies the nucleation of the spherulite germs and describes their expansion rate. To evaluate the effective mechanical properties of the simulated microstructures, the homogenisation method is applied directly to the spherulites, assembled in few classes according to their crystallinity degree. These local properties are then introduced into a new multilinear material model for structural analysis of thermoplastics. Finally, the influence of the microstructure on macroscopic behaviour is outlined for a polypropylene tensile bar, extracted from an injection moulded plate.

Cellular rubber profiles offer a high saving potential with respect to component weight, material consumption and production costs. The foam structure is generated using chemical blowing agents. The blowing agents are incorporated into the rubber mixture before processing. The expansion takes place concurrently to the vulcanisation reaction in the curing unit. Both processes are influenced by modification of the mixture recipe. The adaptation is one of the most challenging steps in rubber processing. Currently, the expansion of rubber mixtures is analysed using modified vulcameters. However, this method is subject to several limitations. Therefore, IKV developed a new measurement system. It allows the analysis of the free expansion behaviour of a rubber sample. Based on the Archimedean principle, the time dependent foaming process of rubber mixtures is recorded. A cell structure is generated, which can be analysed using digital image processing. In the first experiments, several components of the rubber mixture are analysed using the measuring device in order to identify and categorise influencing parameters. The primary objective of further investigations is the analysis of the mixing process. In addition, verification of the results by comparison of the cell structures with industrially foamed rubber materials is planned.

The interaction between hygroscopic surfaces and plasma processes has exemplarily been examined for polyamide 6 (PA6). The water absorption of PA6 significantly influences the plasma processes and thus the resulting surface properties. In a first step the treatment of PA6 in oxygen plasmas was investigated. In etching processes moist surfaces become rougher than dry substrates. They release more water to the vacuum which can be detected by means of OH emission. In a second step PA6 substrates were coated in down-stream plasmas. Plasma polymerisation with HMDSO plasmas is also affected by hygroscopic surfaces. The chemical composition of the coating is influenced by the conditioning state of the substrate and more SiO-bonds are formed in the presence of water.

In ultrasonic plasticizing, energetic ultrasound is used to heat and to plasticize thermoplastic polymers. The basic idea of the process is to deform a material cyclically at ultrasonic frequencies. The deformations are applied on the material by a common ultrasound sonotrode; the plasticization takes place in a plasticizing chamber. The generated melt is directly injected into micro cavities, and hence, micro parts can be moulded easily with the system. In this paper, micro parts being moulded with the process variation “direct injection” are analysed with regard to their weight resulting from the process parameter settings and with regard to their morphology. Furthermore, mixing effects in the plasticizing chamber are being looked at.

Journal of polymers 2016, 3824065 (2016). doi:10.1155/2016/3824065, Published by Hindawi, New York, NY

Due to their wide range of applications and their complex material properties, it is desirable to be able to predict the behaviour of injection moulded parts with the help of simulation tools. For semi-crystalline materials, this can only take place with considerable accuracy if the inhomogeneous material properties are taken into account. Because of this, it is necessary to calculate the microstructure of the solidified melt and to incorporate these findings in the simulation. We present an integrative, multiscale simulation approach in which the manufacturing process is calculated on a macroscale and the solidification process on a mesoscale. A multiphase filling and cooling simulation is done to calculate temperature and velocity fields, which are used as boundary conditions for the calculation of the spherulite distribution in the part. We present the used nucleation and growth model and shortly describe the parallelisation approach of the mesoscale simulation.

Weld lines lead to a significant reduction of the mechanical properties of injection moulded parts. To provide a reliable method for the mechanical design of parts with weld lines, a calculation concept must be developed to predict the weld line strength. For this purpose, a semi-empirical model to describe a reduction factor depending on relevant process influences will be derived from the results of a variety of experimental investigations on stagnating and flowing weld lines. A simulation chain is developed to employ the model in an integrative simulation chain for injection moulded parts.

Light Emitting Diodes (LED) conquer the growing global market of lighting technologies. Due to their advantages, they are increasingly used in consumer products, in lighting applications in the home and in the mobility sector as well as in industrial applications. Particularly, with regard to the increasing use of high-power LED (HP-LED) the materials in the surrounding area of the light emitting semiconductor chip are of utmost importance. While the materials behind the semiconductor chip are optimized for maximum heat dissipation, the materials currently used for the encapsulation of the semiconductor chip (primary optics) and the secondary optics encounter their limits due to the high temperatures. In addition certain amounts of blue UV radiation degrade the currently used materials such as epoxy resins or polyurethanes for primary optics. In the context of an ongoing joint research project with various partners from the industry, an innovative manufacturing method for high precision optics for LED applications made of liquid silicone rubber (LSR) is analyzed at the Institut of Plastics Processing (IKV), Aachen. The aim of this project is to utilize the material-specific advantages of high transparent LSR, especially the excellent high temperature resistance and the great freedom in design. Therefore, a high integrated injection molding process is developed. For the production of combined LED primary and secondary optics a LED board is placed in an injection mold and overmolded with LSR. Due to the integrated process and the reduction of subcomponents like the secondary optics the economics of the production process can be improved significantly. Furthermore combined LED optics offer an improved effectiveness, because there are no losses of the light power at the transition of the primary and secondary optics.

Current models of the injection moulding process insufficiently consider the thermal interactions between melt, solidified material and the mould. A detailed description requires a deep understanding of the underlying processes and a precise observation of the temperature. Because todays measurement concepts do not allow a non-invasive analysis it is necessary to find new measurement techniques for temperature measurements during the manufacturing process. In this work we present the idea of a set up for a tomographic ultrasound measurement of the temperature field inside a plastics melt. The goal is to identify a concept that can be installed on a specialized mould for the injection moulding process. The challenges are discussed and the design of a prototype is shown. Special attention is given to the spatial arrangement of the sensors. Besides the design of a measurement set up a reconstruction strategy for the ultrasound signals is required. We present an approach in which an image processing algorithm can be used to calculate a temperature distribution from the ultrasound scans. We discuss a reconstruction strategy in which the ultrasound signals are converted into a spartial temperature distribution by using pvT curves that are obtained by dilatometer measurements.

The variothermal extrusion embossing process enables a high quality replication of microstructures in plastics films. In this advancement on regular flat film extrusion a polymer melt is shaped by a flat film die and cast on an embossing roll. The surface of the embossing roll has the negative form of the desired microstructure. A counter pressure roll is used to apply the line force needed for embossing, thereby transferring the microstructure into the polymer melt. The melt stays in contact to the embossing roll allowing for a rapid cooling of the film and a solidification of the microstructures inside the molds on the embossing roll’s surface. At the haul-off point the cooled down film is removed from the roll. The governing process parameters for successful embossing are the melt temperature, the viscosity, the surface temperature of the embossing roll and its rotation speed. By tempering the embossing roll to a low base temperature while using an electrical inductor or a high-power infra-red laser as...

This paper deals with investigations of the mixing behaviour of rubber extruders. The requirement to obtain a high-quality elastomer product is a thermally and materially homogenous rubber mixture. Because of the highly viscous and multicomponent nature of rubber mixture, extruders require a thoroughly distributive and dispersive mixing behaviour. The current state of the art is the pin-type rubber extruder with cylindrical pins which extend radially into the screw channel, causing a constant deformation and reorientation of the rubber melt. As mixing is of crucial importance, the mixing behaviour of pin-type rubber extruders is analysed with the goal of optimising it. The starting point of the optimisation is the current cylindrical pins. Over the course of the investigation, new pin designs and geometrical arrangements are investigated.

Thermoplastic materials are increasingly used as a light weight replacement for metal, especially in automotive applications. Typical examples are frontends and bumpers. The loads on these structures are very often impulsive, for example in a crash situation. A high rate of loading causes a high strain rate in the material which has a major impact on the mechanical behavior of thermoplastic materials. The stiffness as well as the rigidity of polymers increases to higher strain rates. The increase of the mechanical properties is superimposed at higher rates of loading by another effect which works reducing on stiffness and rigidity, the increase of temperature caused by plastic deformation. The mechanical behavior of thermoplastic materials is influenced by temperature opposing to strain rate. The stiffness and rigidity are decreased to higher values of temperature. The effect of thermal softening on thermoplastic materials is investigated at IKV. For this purpose high-speed tensile tests are performed on a blend, consisting of Polybutylenterephthalate (PBT) and Polycarbonate (PC). In preliminary investigations the effects of strain rate on the thermomechanical behavior of thermoplastic materials was studied by different authors. Tensile impact as well as split Hopkinson pressure bar (SHPB) tests were conducted in combination with high-speed temperature measurement, though, the authors struggled especially with temperature measurement. This paper presents an approach which uses high-speed strain measurement to transpire the link between strain, strain rate and thermal softening as well as the interdependency between strain hardening and thermal softening. The results show a superimposition of strain hardening and thermal softening, which is consistent to preliminary investigations. The advantage of the presented research is that the results can be used to calibrate damage and material models to perform mechanical simulations using Finite Element Analysis.

Within the Cluster of Excellence “Integrative Production Technology for High-Wage Countries” one major focus is the research and development of self-optimising systems for manufacturing processes. Self-optimising systems with their ability to analyse data, to model processes and to take decisions offer an approach to master processes without explicit control functions. After a brief introduction, two approaches of self-optimising strategies are presented. The first example demonstrates the autonomous generation of technology models for a milling operation. Process knowledge is a key factor in manufacturing and is also an integral part of the self-optimisation approach. In this context, process knowledge in a machine readable format is required in order to provide the self-optimising manufacturing systems a basis for decision making and optimisation strategies. The second example shows a model based self-optimised injection moulding manufacturing system. To compensate process fluctuations and guarantee a constant part quality the manufactured products, the self-optimising approach uses a model, which describes the pvT-behaviour and controls the injection process by a determination of the process optimised trajectory of temperature and pressure in the mould.

The properties of plasma-enhanced chemical vapour deposition (PECVD) coatings on polymer materials depend to some extent on the surface and material properties of the substrate. Here, isotactic polypropylene (PP) substrates are coated with silicon oxide (SiO x ) films. Plasmas for the deposition of SiO x are energetic and oxidative due to the high amount of oxygen in the gas mixture. Residual stress measurements using single Si cantilever stress sensors showed that these coatings contain high compressive stress. To investigate the influence of the plasma and the coatings, residual stress, silicon organic (SiOCH) coatings with different thicknesses between the PP and the SiO x coating are used as a means to protect the substrate from the oxidative SiO x coating process. Pull-off tests are performed to analyse differences in the adhesion of these coating systems. It could be shown that the adhesion of the PECVD coatings on PP depends on the coatings' residual stress. In a PP/SiOCH/SiO x -multilayer system the residual stress can be significantly reduced by increasing the thickness of the SiOCH coating, resulting in enhanced adhesion.

Oxygen and water vapour permeation through plastic films in food packaging or other applications with high demands on permeation are prevented by inorganic barrier films. Most of the permeation occurs through small defects (

The integration and combination of known production technologies to one-step-processes is a promising way to make existing processes more efficient and to enable more integrated products. This paper presents two integrative process technologies that are developed by the Institute of Plastics Processing (IKV) and the Surface Engineering Institute (IOT) as part of the Cluster of Excellence “Integrative Production Technologies for High-Wage Countries”. In these processes, metals or metal alloys are applied to an injection moulded part, which results in a new opportunity to create electrical conductivity of plastic articles. The Integrated-Metal-Plastic-Injection-Moulding (IMKS) represents the combination of injection moulding and metal die-casting, allowing the production of plastic parts with integrated conductive tracks in one shot. The In-Mould-Metal-Spraying (IMMS) combines the injection moulding with the thermal spraying of metal. Therefore it is possible to equip electrically insulating plastic parts with metallic coatings and provide an electromagnetic shielding like cast metal parts. In the following both processes are presented and future potentials and challenges are shown.

The effect of the melt-compounding conditions with the use of a corotating intermeshing twin-screw extruder and of the nanotube content on the morphology and the mechanical and rheological properties of nylon 6/multiwalled carbon nanotube (MWCNT) composites was investigated. The melt-compounding conditions affected the morphology, but the variations in the morphology did not necessarily result in substantial variations in the mechanical and rheological properties. The mass throughput had the strongest influence on the mechanical properties, whereas the MWCNT feeding substantially affected the rheology. The increase in the MWCNT volume content from 0.0 to 3.5 vol % led to an increase in the Young's modulus, whereas the tensile strength, elongation at break, and notched impact strength exhibited maximum values around 0.5 to 1.0 vol %. With increasing MWCNT volume contents, higher complex viscosities and storage and loss moduli and a lower loss factor compared to neat nylon 6 were observed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40893.

The main objective of the presented work is to describe the crystallization kinetics of semi-crystalline thermoplastics with a multiscale model implemented into the COMSOL software and the in-house developed code SphäroSim. The filling and cooling simulations, implemented by using the computational fluid dynamics (CFD) and heat transfer (HT) modules of COMSOL, require the simultaneous solution of non-Newtonian multi-phase flow (polymer/air) and thermal fields in non-isothermal condition and transient regime. The simulation results are collected, converted into the OpenSource file format VTK (Visualization Toolkit) and transferred to the SphäroSim code after a matching operation with the COMSOL mesh. The SphäroSim code uses COMSOL results as input data to compute crystallization kinetics, using the COMSOL data as boundary conditions in the microstructure simulation. This allows the time resolved calculation of the crystallization process and a prediction of the final microstructure in the part which can be used in further simulations such as a structural analysis. The analytical parameters needed to connect crystallization kinetics with molecular material properties and applying the analytical scheme to the numerical simulation during filling and cooling in an injection moulding process are identified.

Production efficiency is one of the most important demands in blown film production. In many cases, the cooling power is the limiting factor for an increased output. A possible solution for a better cooling is the use of a cooling sleeve right after the outlet of the die in addition to the conventional air rings and internal bubble cooling (IBC). At the Institute of Plastics Processing (IKV), first tests were conducted to investigate the advantages of the use of a cooling sleeve. Therefore, the influence of several geometries of the cooling sleeve surface and different cooling sleeve temperatures on the process stability and the mechanical and optical film properties is investigated. The cooling sleeve surfaces differ in the tapping between inlet and outlet diameter from 0 % (cylindric) to 10 % (conical). The tests show that a high amount of tapping as well as too high resp. low cooling sleeve temperatures cause process instabilities and an uneven thickness profile of the film. While the mechanical film properties (E-modulus, elongation at break, tensile strength) of the films produced by the use of a cooling sleeve (cs-films) do not significantly differ from the values of the reference films, the haze of the cs-films was higher and therefore worse. A measurement of the bubble temperatures above the air ring shows that the use of a cooling sleeve can significant lower the bubble temperature at this point. Because of this and because of the results of the mechanical tests, the principle of a contact cooling is generally applicable. Further research and development on the geometry of the cooling sleeve surface has to be done to improve the process stability and the haze for a possible industrial application.

The main objective of the presented work is to develop an integrated computational environment that predicts final part properties made of semicrystalline thermoplastics. This objective is fulfilled by adopting the following two-step approach: 1) identification of an analytical scheme to correlate crystallization parameters with engineer properties; 2) apply the analytical scheme to the numerical simulation to study the polymer and final properties of the part. In this work the crystallization evolution in cooling phase, mainly influenced by thermal gradients, and its effect on the final part properties are investigated. The numerical method, crystallization models and their implementation into numerical software are described as well as the experimental data.

Background: Bioabsorbable implants are not widely used in spine surgery. This study investigated the clinical and radiological findings after anterior cervical discectomy and fusion (ACDF) in an ovine animal model with an experimental bioabsorbable cage consisting of magnesium and polymer (poly-ε-caprolactone, PCL) in comparison to a tricortical bone graft as the gold standard procedure. Materials and Methods: 24 full-grown sheep had ACDF of C3/4 and C5/6 with an experimental bioabsorbable implant (magnesium and PCL) in one level and an autologous tricortical bone graft in the second level. The sheep were divided into 4 groups (6 sheep each). After 3, 6, 12, or 24 weeks postoperatively, the cervical spines were harvested and conventional x-rays of each operated segment were conducted. The progress of interbody fusion was classified according to a three-point scoring system. Results: There were no operation related complications except for one intraoperative fracture of the anterior superior iliac spine and two cases of screw loosening and sinking, respectively. In particular, no vascular, neurologic, wound healing or infectious problems were observed. According to the time of follow-up, both interbody fusion devices showed similar behaviour with increasing intervertebral osseointegration and complete arthrodesis in 10 of 12 (83.3%) motion segments after 24 weeks. Conclusions: The bioabsorbable magnesium-PCL cage used in this experimental animal study showed clinically no signs of incompatibility such as infectious or wound healing problems. The radiographic results regarding the osseointegration are comparable between the cage and the bone graft group. Arbeitsgemeinschaft industrieller Forschungsvereinigungen (AiF) German Federal Ministry of Economy and Technology (BMWi)

Gas transport mechanisms through plastics are usually described by the temperature-dependent Arrhenius-model and compositions of several plastic layers are represented by the CLT. When it comes to thin films such as plasma-enhanced chemical vapour deposition (PE-CVD) or plasma-enhanced atomic layer deposition (PE-ALD) coatings on substrates of polymeric material, a universal model is lacking. While existing models describe diffusion through defects, these models presume that permeation does not occur by other means of transport mechanisms. This paper correlates the existing transport models with data from water vapour transmission experiments.

Caught between the conflicts of economic constraints due to the continuing globalisation and technological standards of maximal product quality, the plastics industry in high-wage countries has to face more challenges than ever. To encounter these challenges of producing in an economical way in the future, further developments of already existing processes as well as new developments are required. Using the example of current developments in the key field of the injection moulding processes at the Institute of Plastics Processing (IKV) at RWTH Aachen University such as lightweight construction, integration of functions, production of polymer optics and surface functionalisation new perspectives of an economic and industrial production in the future Europe shall be pointed out. This paper is based on research made in IKV over the last ten years, so here are given only the references out of IKV., Uhvaćena između konflikata ekonomskih ograničenja zbog stalne globalizacije i tehnoloških standarda maksimalne kvalitete proizvoda, industrija plastike u zemljama s visokim plaćama mora se suočiti s više izazova nego ikada dosad. Kako bi mogla odgovoriti na te izazove proizvodnje na ekonomičan način u budućnosti, potreban je daljnji razvoj već postojećih postupaka, kao i novi razvoj. Koristeći se primjerom trenutačnog razvoja na ključnom polju postupaka injekcijskog prešanja u Institutu za preradu plastike (IKV) na RWTH Sveučilištu u Aachenu kao što su lagane konstrukcije, integracija funkcija, proizvodnja polimerne optike i funkcionalizacija površine, naglasak će biti stavljen na nove perspektive ekonomske i industrijske proizvodnje u budućoj Europi. Ovaj se rad temelji na istraživanju provedenom u IKV-u u posljednjih deset godina, tako da su ovdje dane referencije samo iz IKV-a.

Endlosfaserverstärkte Kunststoffe (FVK) werden bei immer mehr Anwendungen eingesetzt und bieten gleichzeitig eine hohe gestalterische Freiheit. Im Beitrag wird das textile Preforming betrachtet. Zur Darstellung komplexer Geometrien müssen die Fasern bauteil- und belastungsgerecht angeordnet werden. Die textilen Preforms aus Geweben, Gelegen oder Geflechten weisen eine trockene, endkonturnahe, belastungsgerechte Verstärkungsfaserstruktur auf und sind drapierbar bei geringem Verformungswiderstand. Es wurden die Prozessschritte Zuschnitt, Handhabung und Fügen weiterentwickelt. Die automatisierte Verarbeitung von Multiaxialgelegen weist gegenüber der manuellen Fertigung hohe Vorteile bei Stückkosten und Taktzeiten auf. Im Beitrag wird auf das automatisierte Handling biegeschlaffer Preforms näher eingegangen, da hierfür neue Greiferkinematiken und neue Greifmechanismen entwickelt wurden. Abschließend wird auf die Imprägnierung und Formgebung textiler Preforms eingegangen. Es wurden verschiedene Prozessketten wie das Spaltimprägnierverfahren, das Resin Spray Prepregging und das Resin Transfer Prepregging betrachtet.