Mechanism of Polymerization.
Studies of caprolaetam hydrolytic polymerization prior to 1960 represent two major viewpoints: The first view holds that the process consists of polymerization of unstable rings, water and other substanees serving only as catalysts. The second view is that polycondensation of e-aminocaproie acid takes place with concurrent hydrolysis of e-eaprolactam. These viewpoints are probably somewhat one-sided and a better description would be that the overall transformation is rather the result of both polymerization and polycondensation processes. their relative importance depending on various factors, and that every polyeaproamide macromolecule in the process of formation passes through the following three stages (a) initiation; (b) chain growth; and (c) termination (1s4). It has further been postulated that the major chemical equilibria related to polyeaproamide polymerization systems are those of: (a) polymer initiation; (b) chain growth by addition and conensation polymerization (c) redistribution of molecular weight by amide inter change; and (d) regeneration of monomer and oligomer (21 (See also the description of caprolactam polymerization on p. 35G) At one time it was postulated that the polymerization proce via the condensation of aminocaproic acid. It has been concluded. however, that there is too little aminoeaproie acid to permit the rates of polymerization which have been actually observed to be obtained in the condensation reaction. An aminolysis reaction, also referred to as "addition or "transamidation." has been suggested. Initiation and addition are shown by equarion 6 (303)