PEDA index

A comparison of the substituent effects in monosubstituted tetrazole systems and benzene derivatives has been presented (2011T(67)6316). For this purpose the pEDA index (2009JPOC(22)769), defined as the sum of the occupation of 2p orbitals at aU atoms of the ring minus 6, has been used as a substituent descriptor. In aU three cases (substituted benzenes, IH- and 2H-tetrazole derivatives) the pEDA index, which ilLustrates the Tc-electron transfer from the substituent to the ring or vice versa, is weU correlated with constants. A more detailed analysis revealed that the dependence of 2pj, occupancies at the carbon atoms of benzene in either ortho- or para-positions on pEDA values are represented by linear trends with cc= 0.971 and 0.968, respectively. In contrast, the same correlation for the carbon atom in the meta-position is worse cc= —0.791) and with a small... 

When a coating of 1 mm in thickuess containing 7.5% PEDA (% of the initial composition weight) is used, the peak time to the limit state is established, and the intumescence index reaches 6.47 at that. 

FIG U RE 18.4 Influence of PEDA and TEG presence on the intumescence index of coatings. 

---