PH EFFECTS ON PHENOL-FORMALDEHYDE RUNAWAY REACTIONS

Phenol-formaldehyde (PF) polymerizations are commercially important reactions with the unusual ability to react and, if control is lost, self-heat at any pH. A number of experiments were done in the reactive system screening tool (RSST) at formaldehyde to phenol molar ratios (R) between 0.7 and 2.0 in a broad range of pH. It was observed that the runaway reactions are very mild at a pH between 2 and 7, regardless of R. This finding is useful for the consideration and the development of emergency neutralization procedures. Even if phenol-formaldehyde runaway reactions cannot be stopped, at least they can be slowed down before the peak exotherm occurs. It was observed that the extent of the runaway reaction is highly sensitive at pH below 2 and above 7. Commercial compositions should be tested for the worse case scenario i.e., at the low pH limit of the operating procedure for acidic catalysis and the high pH limit for alkaline catalysis.