Abstract
Polyurethane flexible foams have been widely used for automotive seat cushions because of the cushioning performance. It has been required so far to reduce the density of seat cushion foam in Japan. However, recently, improving the riding comfort of seat cushions is considered more important. We have already developed new comfort foams having excellent durability with MDI technologies. Moreover, we have extended our study on high durability foam to improving riding comfort and sitting comfort properties. With regard to riding comfort, we focused on the improvement of static properties such as the stress-relaxation property and the hysteresis loss. We have also investigated the vibration characteristics that are well known as an important factor that affects the comfort performance during driving. The new MDI-based flexible polyurethane foam was developed mainly with MDI prepolymer modification. The MDI prepolymer was re-designed to obtain lower stress-relaxation and lower hysteresis loss. As a result of improving the riding comfort, these foams also provided good pressure distribution properties evaluated with the FSA (Force Sensing Array) system. The improved MDI-based polyurethane flexible foam also showed excellent vi- bration performance as vibration transmissibility of around 3 at resonance frequency and below 0.3 in a higher frequency region. In addition, the improved new MDI-based flexible polyurethane foam also showed excellent durability, and the foam properties were maintained without significant changes under various conditions, even under high humid atmosphere.