Incompatible thermoplastic polymers can be welded by using polymer blends that are compatible with both components.
Ideally, every component in a plastic assembly would be made from the same material. However, cost, functional and aesthetic requirements often dictate that a mix of materials be used.
Unfortunately, such design requirements are not always in synch with assembly requirements. As a result, engineers often have difficulty welding dissimilar plastics, due to chemical incompatibility or widely different melt temperatures.