The Influence of the Roughness of the Welded Surfaces on the Quality of the Weld when using Ultrasonic Welding of Heterogeneous Plastic Materials

To increase the strength of the weld through reducing thermal degradation of the polymer with a lower melting point, it is proposed to use an interleaf layer made of the material whose properties lie in the range of values of basic materials. It is established that one of the factors that determine the strength of the weld and ensure the performance of a heterogeneous polymer composite with a thermoplastic interleaf, is the roughness of the surfaces. It applies not only to the main components of the composite but to the interleaf as well. Adjusting the latter, it is possible to vary the thickness of the welded composites and heat dissipation in the weld area without changing the technological parameters of the welding. Specific features of ultrasonic welding of heterogeneous thermoplastic materials are shown. It has been experimentally confirmed that one of the criteria for weldability of heterogeneous thermoplastic materials must be their compatibility in terms of acoustic properties assessed through density and viscosity. The authors propose technological methods to compensate for variations in the acoustic properties of the welded materials and thus produce high-quality welds. Three stages of the weld formation mechanism are identified when welding heterogeneous plastic materials by ultrasonic welding. An ultrasonic welding machine is developed that incorporates special devices for welding heterogeneous plastics. These include devices for step change of the welding mode, adjusting the temperature of the support and waveguide, heating or cooling of different zones of the welded products.

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