Which are weldable plastics?

There are thermoplastic materials, elastomers, and thermoset resins: Thermoplastic materials are plastics that are processed by heat and are well suited for ultrasonic welding. Elastomers are plastics that are processed by means of cross-linking; they do not react to ultrasonics. The same applies for thermoset resins that are processed by curing and cannot be welded by means of ultrasonics.

Plastic welding is defined as molecular material bonding of thermoplastic materials. As a general rule: only identical thermoplastic materials can be welded homogeneously.

All thermoplastic materials (except PTFE) can be welded. 

PC, PMMA, and ABS can be welded to one another under certain conditions. By means of staking, embedding, and swaging it is also possible to bond other types of materials to thermoplastic materials. Equally, it is possible to bond thin materials, such as PET films or membranes, with rigid plastic parts.

  • Decisive material properties:

    • E-module: promotes sound conduction and determines coupling
    • Damping: promotes heat generation
    • Melting point: determines the heat requirement
    • Viscosity of the melt: high viscous melts can be kept within the joining area more easily, the process sequence is more uniform
  • The following factors have a negative impact on weldability:

    • Additives, such as fire control agents
    • Moisture (particularly in polyamide)
  • The following additives have a positive influence on weld work:

    • Glass fibers
    • Glass beads

    These reinforcement materials predominantly improve the sound conductivity in semi-crystalline plastics.

Classification of plastics and their material properties
The plastics pyramid: Classification of plastics and their material properties


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