November 3, 2026 · admin
Polypropylene (PP) is widely used in packaging, consumer goods, automotive parts and filtration products. It can be welded ultrasonically, but it behaves differently from rigid, amorphous plastics such as ABS, so joint design and machine settings matter.
Why PP Behaves Differently
PP is a semi-crystalline plastic. It has a fairly sharp melting point and absorbs more vibration energy internally, which makes the weld harder to start when the horn is far from the joint. For this reason, PP welds best when the horn contacts the part close to the joint (near-field welding).
Joint Design for PP
- Shear joints often work well for semi-crystalline plastics because they give a strong, sealed bond.
- Energy directors can be used for butt joints, but the design should suit the part.
- Keep parts well supported in the fixture so vibration reaches the joint.
Machine and Process Considerations
- Lower-frequency machines, such as 15kHz or 20kHz, are common for PP because they transmit energy better through the part. See 15kHz vs 20kHz.
- The horn must be designed and tuned for the part.
- Fillers, additives, release agents and surface contamination can all change weld behaviour.
PP Sheets and Corrugated Boxes
Polypropylene sheet and corrugated board can be joined ultrasonically for box and packaging fabrication. See our PP corrugated box welding machines.
Testing Your Part
Because results depend on part geometry and PP grade, the reliable approach is to test a sample. Compare with ABS vs PP ultrasonic welding and send us your component to discuss a suitable machine.
