Structure and physical-mechanical properties related to comfort of flexible polyurethane foams for mattress and effects of artificial weathering

The aim of the work was to test three flexible polyurethane foams for mattress for comfort and durability. In particular, they were investigated the effects of foam composition and cell architecture on some physical-mechanical properties of interest for bedding applications and related to foam comfort levels (i.e. surface firmness, hysteresis loss and resistance to bottoming out), and their changes after artificial weathering due to moisture and temperature. The results demonstrated that all the three foams have open cell morphology and similar cell structure, with average cell diameters ranging from 430 to 510 micron and wide cell size distribution. As a consequence, they also show comparable water vapor transport behavior. On the contrary, their mechanical response, in terms of hysteresis loss, surface firmness and resistance to bottoming out, was found strongly dependent on their chemical structure and molecular mobility, as inferred from infrared spectroscopy analysis. During accelerated weathering all the foams undergo oxidations that affected their comfort factors in static conditions, giving a progressive lowering of hysteresis loss, surface firmness and resistance to bottoming out, particularly for the two foams having lower crosslinking level and thus slow recovery rate after compression.