Abstract: In a method of fusion welding resin articles difficult to melt due to a fusion retarder present in the articles in the form of a fusion retarding element or structure, the articles having surface portions in contact with each other so as to be bonded one to another, a fusion accelerator is applied to the surface portions, with the accelerator being capable of destroying the fusion retarder when heated. After or simultaneously with this step, the resin articles are heated so that the fusion accelerator destroys the fusion retarder, so as to cause the surface portions to melt, before finally allowing the resin articles to cool down.

Abstract: Plastics sheets having edges to be bonded one to another as well as a plastics joint having at least two weldable regions are prepared, each region having an embedded wire extending along the region. Subsequently, the plastics sheet edges are placed on or in the weldable regions, and an electric current is supplied through the wires to emit heat for fusion bonding each edge to the corresponding weldable region. Alternatively, each of the plastics sheets has at least one edge having an embedded wire so that they are welded to each other, without aid of any joint. The joint has U-shaped grooves or ear-shaped protrusions adapted to engage with the plastics sheet edges, and the wires are embedded in the grooves or protrusions.