1. Folders are classified by material, mainly including paper folders, plastic folders, and metal folders. Paper folders are relatively low - cost, environmentally friendly, and easy to print and customize. The common kraft paper folder has a tough texture, can hold a certain number of documents, and is suitable for the temporary storage and transfer of ordinary documents. Plastic folders are highly favored for their waterproof, durable, and non - easily damaged characteristics. For example, the PP plastic folder has a transparent material that allows for quick identification of file contents, and its multi - layer design enables fine - grained classification of files.

2. For plastic folders, the ultrasonic welding effect is excellent. In terms of appearance, the welded part is smooth and beautiful, with no obvious burrs or overflowing material, which does not affect the overall aesthetics and texture of the folder, making the product more competitive in the market. In terms of firmness, the folder welded by ultrasonic welding has a strength at the welded part similar to that of the plastic body, and can withstand large tensile and compressive forces. Even during frequent opening and closing or carrying, it is not prone to cracking or welding detachment, ensuring reliable protection of the files by the folder.

3. In addition, ultrasonic welding also has the characteristics of high efficiency and environmental friendliness. In practical applications, whether it is an ordinary single - layer plastic folder or a complex multi - layer, multi - functional plastic folder, ultrasonic welding technology can accurately achieve the firm connection of various components, providing users with high - quality folder products.