Which kind plastic material could be welded by ultrasonics

I believe everyone is familiar with the ultrasonic plastic welding machine, because it has been widely used in our lives. But which materials can be welded by ultrasonic, you must have such doubts, and when you ask the manufacturer, the manufacturer will ask you what material the product needs to be welded. Here is a list of the following, to share with you.

Amorphous polymer (ABS, PC, PS, PVC, PMMA, etc.): The molecular arrangement is disordered, and the material gradually softens, melts and reaches the temperature (Tg glass transition temperature). This type of resin is usually able to effectively transmit supersonic vibrations and achieve good welding in a fairly wide range of pressure/amplitude.

Crystalline polymers (PE, PP, POM, PA6, PA66, PBT, PET, etc.): molecules are arranged in an orderly manner, with obvious melting points (Tm melting temperature) and re-freezing points. The solid crystalline polymer is elastic and can absorb some high-frequency mechanical vibrations. Therefore, this type of polymer is not easy to transmit the ultrasonic vibration energy to the pressing surface, which helps to require higher amplitude. It takes very high energy (high heat of fusion) to break the semi-crystalline structure and make the material change from the crystalline state to the viscous flow state. This also determines the obviousness of the melting point of this type of material. Once the molten material leaves the heat source, A decrease in temperature will result in rapid solidification of the material.

Secondly, generally speaking, non-polar compounds (such as PP, PE) are more difficult to sonicate (but not impossible), polar compounds can be sonicated, and polar compounds can also be sonicated, such as ABS and PMMA. It can be ultrasound.

In addition, there are some characteristics that affect the effect of ultrasonic, such as hardness (the higher the hardness, the better the ultrasonic welding), the melting point (the higher the melting point, the more ultrasonic energy is required), and the purity (the welding effect of raw materials is good, and recycled materials are mixed. The impurity effect is slightly worse)