Quantification of the mechanical properties, such as the non-linear viscoelastic behavior, for a cured sealant is complicated by the presence of the Mullins Effect. The Mullins Effect, commonly observed in elastomers, refers to an observed increase in the measured modulus the first time an elastomer is mechanically loaded. This paper examines the Mullins Effect and the non-linear viscoelastic behavior of five different sealants encompassing the range of properties and formulations found in commercial samples. The non-linear viscoelastic behavior of these five materials was examined using stress-relaxation experiments. Although the behavior was complex, the time dependence and strain dependence were found to be relatively independent so time-strain superposition could be used to simplify modeling and characterization. A simple empirical equation was formulated to describe all five sealants over a wide range of strains and time scales. The Mullins Effect was observed in all sealant formulations studied. Moreover, this effect was observed in both tension and compression strains. Finally, there was a recovery of the Mullins Effect after sufficiently periods of time between repeated loading cycles. A set of simple rules was formulated to describe the Mullins Effect in sealants. The tests demonstrate that understanding the Mullins Effect is crucial in characterizing the mechanical properties for a sealant.
Citation: Journal of Polymer Science Part B-Polymer Physics
Pub Type: Journals
durability, elastomer, material properties, Mullins effect, non-lenear rehology, sealant, stress-relaxation, stress-strain, viscoelasticity