| 摘要 |
In a process for joining the edges of a continuous strip of polyethylene film to a polyethylene mesh substrate by fusion welding, either a strand of semi-molten polyethylene is extruded between each edge and the substrate before compressing to bond them together, or an appts. is used which selectively heats and compresses those parts of the film in contact with the filaments of the mesh, but not those covering the interstices in the mesh. In the first instance, a rectilinear casing is formed by the strip, the mesh and the extruded strands. This may be used to house a pre-positioned multi-filament polypropylene ribbon. The mesh is laid on top of underground pipelines to warn mechanical digger operators, etc. of their position. The polypropylene further increases visibility. The mesh is easily broken when pulled up by an excavator, but the stronger polypropylene is drawn out of its sleeve by the jaws of the excavator before bursting into a large number of easily seen fibres. |
