Which of the following joints requires an adhesive for bonding?

The requirement for an adhesive in bonding is specifically associated with a plastic adhesive joint, making this the correct answer. Plastic adhesive joints utilize adhesive materials to bond two plastic components together, ensuring a strong and durable connection. Adhesives create bonds at the molecular level, which can accommodate a range of stresses depending on the type used.

In contrast, other types of joints mentioned do not primarily depend on adhesives for their bonding process. For instance, a plastic heat fusion joint relies on the application of heat to melt the edges of the plastic parts, allowing them to fuse together once cooled. Similarly, welded joints are formed by melting base materials together and allowing them to cool to form a strong joint, while soldered joints involve the melting of a filler metal to join two metal parts without melting the base metals themselves. These processes do not require adhesives, highlighting the unique nature of the plastic adhesive joint that relies on chemical bonding rather than thermal or mechanical methods.