Specific Surface and Degree of Dispersion

The specific surface of (phenolic) plastic foams was first measured by Schauer, Truxa and Spitzer in 1967 using the BET method They obtained a value of about 2 m /g. 

The high specific surface of PUR foams (F. 2) reaching 140 m /g (7 = 40 kg/m was mentioned above. According to our data the value of S is 5—10 m /g for phenolic foams, whereas Fedodeev and Litvinova obtained much higher values, 425 m /g, corresponding to a degree of dispersion of 8.4 lO cm (these data will be discussed on p. 40 tr ether with the problem of water absorption, see Table 6). 

These great differences are presumably due to the different measirement techniques we used mercury porosometry and the BET method whereas the authors of estimated S by water absorption. 

It should be noted that very high specific surfaces (S 3(K) m /g) have als) been reported for some microporous (non-foamed) RO systems, including urea-formaldehyde polymers  

In classical colloidal chemistry, solid foams were traditionally ass ed to low or coarse dispersion systems, i.e. to systems with minimal pore (cell) sizes of about 1 im or more and with a degree of dispersion (specific surface) of 10 - 10 cm .  

---