The performance of plastics affects the effect of ultrasonic welding. The ultrasonic welding properties of plastics depend on the plastics' ability to attenuate ultrasonic vibrations and the melting temperature as well as physical properties such as elastic modulus, impact resistance, friction coefficient and thermal conductivity. In general, the greater the hardness of a plastic product, the easier it is to weld. Plastics with high hardness tend to transmit ultrasonic energy, while soft plastics often attenuate energy before energy reaches the joint area. The hardness of plastic products will also vary with ambient temperature and humidity. Pigments, mold release agents, glass fillers and reinforcing fibers have a greater impact on it.
Effect of fillers and reinforcements on ultrasonic welding
Fillers (glass, talc, minerals) in thermoplastics can improve or inhibit ultrasonic welding. Materials such as calcium carbonate, kaolin, talc, aluminum hydroxide, organic fillers, silica, glass spheres (wollastonite) and mica can increase the rigidity of the resin and increase the overall material (especially semi-crystalline plastics) at up to 20%. ) ultrasonic energy transfer performance. At a level of up to 35%, there may be a shortage of thermoplastic resin at the joint where a reliable hermetic seal is required. When the filler reaches 40%, the fibers accumulate at the joint surface, and the thermoplastic material is insufficient to form a firm connection. Long fibers may accumulate during the molding process, causing the conductive ribs to contain a higher percentage of glass than the matrix material. This problem can be solved by using short fiber glass filler. Abrasive particles in many fillers cause weld head wear when the filler content exceeds 10%. It is recommended to use hardened steel or hard alloyed titanium welding heads. It may also be desirable to have a higher power ultrasonic device to generate sufficient heat at the joint.
