Experiments with hot tool joining of thermoplastics to metal

With the requirements for increasing fuel efficiency of automobiles lightening of structures would require joining of dissimilar materials like metals to plastics. In this study, thermoplastics were joined to metal using a heated tool. The metal substrate was textured with a fine knurl pattern and heated for a preset time by pressing it against a hot tool that was kept at a high temperature. Then the metal part and hot plate were retracted, and the cool thermoplastic sheet was pressed against the hot metal surface for a preset time. The hot metal would then melt the thermoplastic surface resulting in flow and wetting and joining of the parts together. Increasing the heating time generally increased the joint strength until an optimum was reached. HDPE to steel joints were slightly stronger and more consistent than HDPE to aluminum joints. For a fixed heating time, the PC and HDPE steel joints were stronger than PP and acrylic to steel joints.