Polymerization
Furthermore, creep and creep recovery of a material can be analyzed by a four-element
model (Fig 5). When a constant stress is applied at t = 0, the material shows an instantaneous
increase in strain (the spring E1), followed by a gradual increase in strain (the spring E2 /
dashpot η2 and dashpot η3). On removal of the stress, the spring E1 recovers instantaneously
followed by gradual recovery of the spring E2 / dashpot η2. Some permanent deformation
remains as a consequence of the dashpot η3 [2].