Interaction Between Foam Injection Molding and Welding Process

Analysis of the Process - Material - Structure - Property Relations
  • Karoline HofmannEmail author
  • Christian Brütting
  • Michael Gehde
  • Volker Altstädt
Conference paper


Due to increasing demands on component integration, functionalization, saving weight or material, the density and weight of thermoplastic parts could be influenced significantly by using the thermoplastic foam injection molding process.

The characteristic three-layer structure offers numerous advantages for applications, such as weight reduction, increasing the specific bending stiffness with a simultaneous low tendency to warp and optimizing thermal and acoustic properties. For a subsequent joining process, however, difficulties arise due to the thin solid skin layer. Minimum joining distances during welding can no longer be met geometrically and the mechanical properties of the components are reduced.

The present study is intended to analyze the interaction between the microcellular structure of the injection molded parts, the influence on the joining process and the resulting mechanical properties. Therefore, a cooperation of Chemnitz University of Technology and University of Bayreuth was founded to investigate the correlation between injection molding and vibration welding for microcellular polypropylene and polyamide materials.

In addition to various materials with and without fiber reinforcement, the influence of storage time and different joint types were investigated in this study.

The aim of this study was to gain a deeper understanding of the relationships between process, material and its structure as well as the development of processing guidelines which can be transferred to industrial applications.

The results show that the characteristic three-layer structure has a considerable inhomogeneity, depending on the used material, the foaming process and the process parameters.

However, the weldability of foamed thermoplastics strongly depends on the internal structure due to the injection molding parameters, the storage time between foam injection molding and welding process, the joint type and the welding process itself.


Foam injection molding Physical foaming Chemical foaming Vibration welding Parameter variation 



The investigations were carried out in cooperation of the University of Bayreuth, Polymer Engineering Bayreuth.

The investigations were promoted from budgetary funds of the German Federal Ministry of Economic Affairs and Energy (BMWi) on the basis of a decision by the German Bundestag via the German Federation of Industrial Research Associations (AiF) We would like to record our appreciation of this support.

Furthermore, we thank the companies Lanxess Deutschland GmbH and LyondellBasell Industries for providing the material.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2020

Authors and Affiliations

  • Karoline Hofmann
    • 1
    Email author
  • Christian Brütting
    • 2
  • Michael Gehde
    • 1
  • Volker Altstädt
    • 2
  1. 1.Professorship of Plastics EngineeringChemnitz University of TechnologyChemnitzGermany
  2. 2.Polymer Engineering BayreuthUniversity of BayreuthBayreuthGermany

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