Creep/recovery behavior of open‐cell foams

Abstract Static measurements have been used to predict the dynamic response of ldquo;unboundedrdquo; open‐cell noninked (dry) and inked foam materials. Creep, e c (t) , and recovery, e r (t) , were determined in compression from static and dynamic modes. Force measurements, f (t) , and strain decay, e (t) , were used to determine the change in creep, δ e c (t) . The change in creep represents the plastic strain, e p1 (t=t h ) , and is uniquely defined by the recovery function, e r (t=t h ) , where t h is the hold time. Creep and recovery results of various classes of foam materials and nonfoam materials were found to fit a master curve of the form F r (t) =exp[– k ′ r ( t h ) t ] = [e r ( t ) ‐ e 00 ( t h )]/[e 0 ( t = 0) ‐ e 00 ( t h )] at a reduced time of k ′ r ( t h ) t [ k ′ r ( t h )] C 0 /( t h ) a (where Co depends on the material's “dry” or “wet” state), a is a function of the type of material, and em is the permanent set]. These empirical results are applicable to printing ink transfer and print quality. Other important factors of concern are diffusion processes within the polymer matrix and the nature of the polymer (e. g., chemical constitution, porosity, molecular weight, and solubility). © 1995 John Wiley & Sons, Inc.