Ultrasonic welding (ULTRASONIC welding) is a method of connection of different materials in the solid state using the ultrasonic vibrations. With the help of ULTRASONIC welding is well connected polycarbonate, styrene, polypropylene, polyvinyl chloride, and artificial leather, natural fabrics with synthetic fibers and many other polymeric materials, and combinations thereof.
Ultrasonic welding (ULTRASONIC welding) is a method of connection of different materials in the solid state using ultrasonic oscillation. With the help of ULTRASONIC welding is well connected polycarbonate, styrene, polypropylene, polyvinyl chloride, and artificial leather, natural fabrics with synthetic fibers and many other polymeric materials, and combinations thereof.
The greatest application of ULTRASONIC welding is found for the connection of polymeric sheet products.
– possibility of welding with contaminated or covered by foreign films surfaces
– ultrasonic welding does not (i.e. no) overheating of the material,
– obtaining of connections in hard to reach places
– welding of materials with a narrow interval of crystallization,
ultrasonic welding gives the possibility to combine different polymer materials
– the strength of the connection is usually from 50 to 70% of the strength of the connected materialthat is approximately 2-2,5 times higher than in welding and thermal method.
The principle of the device for welding of polymer sheets (films) is as follows. Polymeric sheets superimposed on one another, tightly pressed to each other and to the support, then down with the necessary force to the welding tool leaves (the tip) connected to the ULTRASONIC transducer, and includes a generator, actuating the ULTRASONIC transducer.
Under the action of stresses of ultrasonic frequency elasticity of the polymer increases or throughout the volume between the welding tip and a support (when welding thin films) or only to the extent of the contact zone of the connected materials which are naturally or artificially caused irregularities of the mating surfaces (welding of large parts).
While initially formed by physical contact of the surfaces and the activation of polymer molecules by rupture of chemical bonds, and then starts the chemical interaction between joined materials, resulting in a volumetric interaction in the connection area. Hysteresis loss during the deformation of the polymer material with ultrasonic frequency leads to its heating to temperatures corresponding to the viscous-flow state (of amorphous polymers) or melting of the crystals (partially crystalline polymers). At temperatures highly elastic state of the polymer is diffusion of individual segments of macromolecules between the two polymers, and in some cases – and stirring viscous polymeric material. When joining two thermoplastics of different grades occur chemical transformations. The value segment of the macromolecule determines the weldability of the material: the greater the segment (“harder” macromolecule), the better the weldability.
The strength of the connection depends on the physico-mechanical characteristics of the weld geometry and dimensions of the ultrasonic tool, the static stresses in the weld zone. Usually, the strength of the connection is from 50 to 70% of the strength of the joined materials. It is approximately 2-2,5 times higher than in welding and thermal method. Joint width equal to the width of the tip of the tool. The thickness of the joined materials ranges from a few microns (film) to a few millimeters (tissue, body parts).