Edmund Haberstroh

Influence of carbon black pigmentation on the laser beam welding of plastics micro parts

By means of laser beam welding it is possible to join plastics parts in micro system technology. Based on existing macroscopic process variants, an appropriate process technology for laser beam welding in order to join plastics micro parts has been developed at IKV. For welding of plastics parts, the influence of material and process parameters on the quality of the weld lines has been investigated. Apart from these studies, a strong effect on the welding process is expected when using different filling materials like, e.g., carbon black. Investigations of microscopic melt zones produced by the focused laser beam are presented.

MODELLING AND SIMULATION OF THE FOAM FORMATION PROCESS

In order to optimise existing process techniques, it is necessary to achieve a more accurate estimate of the PU material behaviour during the moulding process, before production actually commences. At present, the lack of appropriate material models means that the computer-aided prediction of the mould filling process for PU foam systems with simulation programs is only possible to a limited extent. For this reason, a model is presented of the density development during foam formation, which is based on an experimental characterisation of the foaming process. This model has been implemented in a program for simulating the filling process. In order to assess the quality of the model formulation selected, the calculated mould filling is compared with the results of an experimentally-conducted filling study. The investigations have shown that the mould filling behaviour for foaming processes that are constrained by mould walls can be readily described with the aid of the simulation. For free foaming processes, however, the elastic properties of the foam that develop have been seen to be a key material parameter that will need to be taken into account in future.

Multi-component injection moulding of liquid silicone rubber/thermoplastic-combinations

The two-component injection moulding method allows the production of parts consisting of two components which are arranged next to or above each other (overmoulding). Besides well known combinations between thermoplastics and thermoplastic elastomers (TPE) which are used in various applications, the combination of Liquid-Silicone-Rubbers (LSR) and thermoplastics becomes more important because of their better mechanical and thermomechanical properties as well as the chemical resistance in comparison with TPE. These combinations of LSR and Polyamid can be a new alternative for combinations made of rubber and metal, which often require a costly preparatory treatment. Concerning the adhesive strength of these combinations, which depends on the properties of the materials, the process parameters in the moulding process and the mould technique, there is only insufficient knowledge. To solve this, the IKV developed techniques to meet the requirements. Results of the investigations in this context will be presented.

LSR thermoplastic combination parts in two-component injection molding

This paper presents research in the field of overmolding which is an important technique within multi-component injection molding. Two different materials are injected via two separate gating systems into the cavity sections. The resulting part consists of two layers which lie next to each other or on top of each other. The main focus of the research of these compounds is on the adhesion between the two components, which up to now could not be predicted or determined sufficiently - especially regarding the influence that process parameters have on the adhesive strength of the parts. This paper presents compounds made of LSR and thermoplastics, giving detailed description of the materials and of different ways how to determine the adhesive strength of rigid flexible combinations.

Processing and properties of novel reinforced polymer blends made of polymers and low-melting glass

The increasing requirements for technical polymers have resulted in the development of novel polymer blends where glass with low melting points substitutes glass fibers or spheres. These blends offer many commercial opportunities especially for high-end applications in electronic components. Typical material properties for polymer/glass blends are high stiffness and strength in combination with an excellent frictional behavior. The fact that the different components of these blends have extremely different viscosities results in special demands on the compounding process.

Reactive blending of incompatible polymer systems containing polyamide and PET

In general, blends of PA and PET are of minor significance in industrial production due to the thermodynamic incompatibility of their components. An economic and ecological interest in producing such blends may increase especially since the European beverage industry decided to use (multi- and single-layer) PET bottles. PA/PET blends also appear to offer an interesting alternative from the technical point of view. The less expensive PET could be used more widely for injection molding applications, while improved mechanical properties are expected at the same time. In this paper an optimized compounding method is presented for production of compatibilized PA/PET blends by reactive extrusion.

The use of modern technologies in the development of simulation software

For modelling purposes, complex technical processes are frequently broken down into elementary sub-processes, which are subsequently simulated with different programs and methods. This can only be done effectively if the individual programs are linked in terms of their contents. In order to create programs and program systems in such a way as to meet these requirements, processes are being analyzed and formalized at the IKV using the very latest computer science methods. The data models developed in this project will permit a program to be structured on a modular basis. Existing simulations are being seamlessly integrated into the structures being developed at the analyses stage. The structure of MOREX, the newly designed simulation program for the design of twin-screw extruders, was developed from these data models and is described here by way of an example. The program can easily be extended, and any missing functions can be integrated from existing modules.

Progress in the characterisation of the polyurethane-specific material behaviour

The development of the Gas-assisted-Reaction Injection Moulding (G-RIM) technique has been the subject of research activities at IKV for some years. To understand and explain the process phenomena observed in the Gas-assisted-Reaction Injection Moulding (G-RIM) technique, the reaction kinetics and rheological material behaviour needs to be examined. This is the subject of ongoing research activities at IKV. In this paper investigations on the rheokinetic and rheological material behaviour of a slow-reacting compact PU system are presented and mathematically described. The investigations have shown that the model developed for describing the reaction kinetics and the temperature and viscosity field reproduces the material behaviour under the real process conditions with a good degree of accuracy.

GAS-ASSISTED REACTION INJECTION MOULDING (G-RIM) OF POLYURETHANES - NEW DEVELOPMENTS

For some time the development of the Gas-assisted-Reaction Injection Molding (G-RIM) technique, which is expected to combine the process-specific benefits of the gas injection technique and the outstanding material potential of polyurethanes (PU), has been the subject of ongoing research activities at IKV. In this paper further investigations into the moulding process are presented, with the aim of evaluating the feasibility of the G-RIM process for industrial use. Therefore two PU formulations with reaction kinetics similar to those encountered in practice are used. One of these is a minimally crosslinking, segmenting PU elastomer (compact), while the other investigation is focused on the process behaviour of a compact casting PU system that undergoes pronounced crosslinking. It was seen that segmenting, flexible polyurethanes with their lower crosslinking density, and the resultant pronounced or less pronounced thermoplastic phase that results from this during curing, have a greater processing window than is the case for systems that undergo pronounced crosslinking. Moreover it is shown in first trials that even moulding of complex shaped parts - a media duct for example - is possible.

BATCH VARIATIONS AND THEIR EFFECTS ON THE ELASTOMER-PROCESSING ILLUSTRATED ON THE MODEL OF THE INJECTION MOULDING PROCESS

For elastomeric materials the part moulding process and therewith the part properties are influenced by the production conditions during the mixing period to a major extent. Based on an analysis of the whole process chain, the influence of batch fluctuations in rubber injection moulding is discussed and the information value of different material testing procedures is evaluated regarding the further processing. Furthermore, details of the potential of artificial neural networks (ANN) and regression analysis are given by establishing an overall process correlation between the individual process parameters and the properties of compound and part.