How to use ultrasonic welding for non-woven fabrics?
Some indentations can be seen everywhere on the mask, such as the edges, ear straps, and exhalation valve are all ultrasonically welded.
In the production process of masks, we can intuitively understand the welding of all-plastic nose bridge, welding after hemming, breathing valve welding, multi-layer seam welding, ear band welding, these are actually completed by ultrasonic welding process.
When ultrasonic waves act on the thermoplastic plastic contact surface, it will produce tens of thousands of high-frequency vibrations per second. This kind of high-frequency vibration with a certain amplitude will transmit the ultrasonic energy to the welding area through the upper weldment. Because the welding area is two The acoustic resistance at the welding interface is large, so local high temperature will be generated.
Because of the poor thermal conductivity of the plastic, it cannot be dissipated in time for a while, and it gathers in the welding area, which causes the contact surface of the two plastics to melt rapidly. After a certain pressure is applied, they merge into one.
After the ultrasonic stops acting, let the pressure continue for a few seconds to make it solidify and shape, so that a strong molecular chain is formed to achieve the purpose of welding, and the welding strength can be close to the strength of the raw material.
Non-woven fabrics are the most used in the environmental protection, medical supplies industry. Like the liquid filter bag sealing and tail sealing are achieved by welding, after welding, it is waterproof and leak-proof, with high strength.
