Gelation Reaction of Soil Stabilizer of Urea-Formaldehyde Condensate Type

Abstract

The purpose of this study is to reveal the chemical characteristics of gelation reaction of the soil stabilizer. Analysis of composition of the soil stabilizer (Table 1) and the gel (Table 2 and Fig.3) showed that 80% of formaldehyde in the soil stabilizer exists as the form of N, N'bis(hydroxymethyl)urea (BHU) and the gelation process is essentially an acid-catalyz e d condensation reaction of BHU with urea. The“gel”was found to be the condensation products of 2 molecules of BHU with 1-3 molecules of urea, i. e., N, N'-bis(hydroxymethyl)-5oxo-2, 4, 6, 8-tetraazanonanediamide 7, N-hydroxymethyl-5, 9-dioxo-2, 4, 6, 8, 10, 12-hexaazatridecanediamide 5 and 5, 9, 13-trioxo-2, 4, 6, 8, 10, 12, 14, 16-octaazaheptadecanediamide 6, depending on the amount of urea added. Effects of gelation conditions such as gelation time (Table 4), amount of urea added (Fig.6), concentration of sulfuric acid (Fig.7), amount of water added (Fig.8) and gelation temperature (Fig.9) on the gelation reaction were also examined. These results are consistent with the proposed reaction scheme which includes the formation of Nhydroxymethyl2, 4-diazapentanediamide 8 as a common intermediate (Reaction Scheme of Gelation).