Premium
Equation of consumption rate of free‐radical vinyl polymerization. II
Author(s) -
Sasaki Hideki
Publication year - 1968
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1968.070120610
Subject(s) - monomer , polymerization , radical polymerization , reaction rate constant , polymer chemistry , polymer , chemistry , bulk polymerization , yield (engineering) , constant (computer programming) , kinetic chain length , radical , materials science , kinetics , organic chemistry , composite material , physics , quantum mechanics , computer science , programming language
The vinyl polymerization reaction is a two‐molecule reaction. However, it is more convenient to use a specially defined rate constant than to use the general constant, because a new radical is formed instantaneously in the same radical compound when one monomer combines with an existing radical in a living polymer or an initiator radical. This special rate constant is named the propagation constant and is proportional to the concentration of monomer when the polymer is formed from a unit mole concentration of the initiator radical. The specific propagation constant is related to the concentration of monomers which react in unit time and unit concentration of monomer and radical. Arnett's experiments are discussed in terms of the equation formulated. The value of Δ[M]/([M] 0 · t ) is found not to be a reaction rate but a value of ln [M] 0 /[M] when [M] 0 – [M] is very small. Autoacceleration of the polymerization is found with high concentrations of monomer which yield an increase in the velocity of propagation and also at low concentrations of initiator, which cause prolongation of the propagation stage. When the concentration of initiator is high, this phenomenon does not take place until enough initiator is consumed and the necessary low initiator level is reached. The time required is called the induction period. The larger the polymer molecule is, the higher the viscosity becomes.