Dynamic H-Point Loss of MDI and TDI Automotive Seating Foams and a Method to Predict it

摘要

There are several competing technologies to choose from when making automotive seating foam. TDI, TM, MT and MDI based seating foams are all in production at this time. Things like cure time, flowability, density, dual firmness and humid aged properties play to the different strengths of TDI and MDI based foams. This paper compared the technologies by measuring how the H-point of a built up seat changes with time during a ride evaluation. It also looked at a way to predict the H-point behavior using test blocks instead of fully built seats. Parts were made using both a standard MDI and standard TDI based system. These parts were made at 3 different densities while maintaining the hardness of each cushion and back. The pads were covered with standard fabric and placed on standard frames. The built up seats were subjected to 3 hour "rides" by placing them on a single axis shaker table and subjecting them to a simulated ride. The H-point was measured using two different test methods after 1 hour of simulation, 3 hours of simulation as well as 22 hours after simulation.. The results showed that TDI and MDI based foams performed similarly. Test blocks were also made and tested on a hydraulically actuated test machine using a previously developed test method to determine if a correlation could be made between the test blocks and the fully built up seats. The results showed that the test method was highly affected by the hardness of the foam and did not correlate to the H-point measurements of the fully built seat.