Chemistry Reference
In-Depth Information
Figure 6.6 The typical compressive behavior of bio-based PU foams with different
isocyanate indexes.
Adapted from ref. 3 with permission from Springer Science. 1-neat PU
foam; 2-with 2.5 parts of wood fiber; 3-with 2.5 parts of microclay.
fibers act as polysaccharides. Smaller fiber particles mean lower hydroxyl
functionalities. That is the reason that both the tensile and compressive
strength decreased following the decrease in fiber size (Figure 6.9). It is known
that PU spray foams have higher thermal stabilities whenmore water is used as
the blowing agent.
6
Like water, the amount and size of wood fiber particles
effects the thermal stability of PU foams. Gu has reported that larger wood fiber
particles and a higher content of wood fiber produced PU spray foams with
higher thermal stabilities, as indicated in Tables 6.1 and 6.2.
