An evaluation of cast PVC processing conditions for improved adhesion to polyurethane foam for automotive applications
By Robert Bondar
Although the process of laminating cast PVC cover skins over polyurethane foam is well known, it is becoming increasingly clear that failure to account for the skin colour, the roughness of the skin at a nano level and the skin casting temperature can all lead to significant variability in the overall performance of the finished composition.
This article will explain why these parameters are important when trying to create a superior PVC/PU composite, and why the widely used quality control measurements of dyne value and contact angle of cast PVC skins are not good guides to performance in use.
Cast PVC cover skin is often used for higher quality automotive interior trim, and is frequently used in combination with polyurethane (PU) foam in the production of interior components such as door and instrument panels.
Good adhesion of the PVC skin to the PU foam is critical for good part performance and service life. However, tests of adhesion between PU foam and cast PVC used in the automotive sector have shown wide ranges of results.
At the bottom end of the range, we see undesirably low ply-adhesion forces of less than 50 N/m (0.3 lbf/in). Composites with this behaviour exhibit complete adhesive failure,…