ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
The mechanical behavior of various classes of inked and non-inked (dry) open-cell foam rollers has been investigated from stress/strain measurements in compression. Hysteresis, creep, and recovery in dynamic loading were used to differentiate the rollers as to their utility in printing applications. Creep, ∊c(t), and recovery, ∊r(t), were determined in a compression mode from force measurements and strain decay, ∊(t), i.e., Δ∊c(t) = ∊0 - ∊(t) [∊0 = ∊(t = 0)] or ∊c(t) = 2∊0 - ∊(t). The creep function, Δ∊c(t), represents the plastic strain, ∊pl(t = th), and is uniquely defined from the recovery function, Δ∊c(t) = ∊r(t = th), where th is the hold or contact time. The recovery results for a polyurethane ester (PUE) and acrylonitrile/butadiene (AB) rollers (dry/ink), poly(vinylidene fluoride) film (PVF2) (air/vapor) and low-density polyethylene film (LDPE) (air/vapor) were found to fit a master curve of the form Fr(θ) = EXP[-Kr(th)θ] = [∊r(t) - ∊∞(th)]/[∊0(t = O) - ∊∞(th)] at a reduced time of Kr(th)θ {θ = t/th and Kr(th) = k′r(th)th = C0/(th)α-1 (where C0 depends on the material's “dry” or “wet” state, α is a function of the type of material, and ∊∞ is the permanent set). These empirical results are consistent with the observed decreases in print intensity during transfer to a paper substrate and weight changes of the roller, i.e., creep and recovery are important in the printing characteristics of a given roller material. Other factors of importance in the overall transfer and print quality, but of longer-term considerations, are diffusion processes within the polymer and the nature of the polymer (e.g., porosity, chemical constitution, surface and interfacial tensions).
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760321005
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