What thermoplastic materials can be bonded by ultrasonic plastic welders? Can I weld dissimilar thermoplastics?
Weldable thermoplastic resins can be categorized as amorphous or crystalline.
Weldable AMORPHOUS resins include: polycarbonate, polyphenylene oxide, polystyrene, ABS, polyetherimide, acrylic, and polysulfone. Weldable CRYSTALLINE materials include: thermoplastic polyester, nylon, acetal, polyethylene, polyphenylene sulfide, and polypropylene.
Yes, a limited number of dissimilar, amorphous thermoplastics can be welded together (e.g., ABS and polycarbonate). Melt temperature difference for dissimilar materials can’t be greater than 50° F.
Will my plastic material still bond ultrasonically if it has a fire retardant treatment?
Flame retardants can affect the weld by reducing the strength of the bond. In such cases, “overwelding” can sometimes be the solution. This involves utilizing a higher amplitude machine or a slightly longer weld time to create a sufficiently strong bond.
What is an acceptable amount of glass content for ultrasonic welding of plastics?
Up to 20% is preferred. However, adequate welds can sometimes be achieved with up to 30% glass filler.
What are the common joint designs for plastic welding?
The so-called “energy director” approach is used for many joints. This requires a triangular projection be used on one of the pieces being joined and placed where the melting initiates. For leak-tight joints and some semi-crystalline parts, a shear joint is recommended. A shear joint requires some interference between the parts to be welded. As the parts are ultrasonically heated and compressed, one part “shears” softened plastic from the other.