Functionality in phenol-formaldehyde step-growth polymerization

Abstract

Fundamental concepts of functionality within polymer systems are restated, with particular reference to the phenol-formaldehyde (P-F) step-growth polymerization. The functionality of both reactants is governed by the stoichiometry. A distinction between the number of functional groups (potential functionality) and actual functionality is made. At the extent of reaction used in practical systems when P/F > 1 (i.e. novolacs) the actual functionality of formaldehyde will always be two, while the actual functionality of phenol will approach a maximum of two. When P/F < 1 (i.e. resoles), a more complex situation arises, with formaldehyde never achieving an actual functionality of two while phenol..