Crack propagation behaviors in a nanoparticle‐filled rubber studied by in situ tensile electron microscopy

Abstract

Although fracture resistance is critical for rubber materials, the fracture mechanisms are poorly understood from a microscopic perspective. In this study, a crack propagation process in rubber with silica nanoparticles, which is commonly used to enhance the mechanical properties of rubber materials, was successfully observed in situ with nanoscale resolution using transmission electron microscopy (TEM). The consecutive time-sliced TEM images clarified that the crack tip propagated along the interfaces between the rubber matrix and aggregates of silica nanoparticles (rubber-aggregate interfaces). Moreover, the path and propagation rate of the crack were significantly affected by the heterogeneous distribution of the silica aggregates, which resulted in a "stickslip" propagation behavior of the crack tip. Detailed spatial strain analysis revealed that the local maximum principal strain (ε max ) around the crack tip was nonuniform. The crack tip propagated through regions with large ε max , delaminating the rubber-aggregate interfaces. This study successfully demonstrated that the heterogeneous distribution of nanoparticles significantly affects the fracture behavior of nanoparticle-filled rubbers.

Real‐time observation of microcrack growth in thin film microtomed from rubber/nanocellulose composite sheets, during tensile deformation

“…Specially designed TEM sample holder for real‐time observations during tensile deformation [ 26–30 ] …”

“…Specially designed TEM sample holder for real-time observations during tensile deformation [26][27][28][29][30] counted as part of the rubber component. The weight ratios of ZnO, [32,33] the cross-linker, and anti-aging agent to the rubber component were set to be the same in the two composite sheets.…”

“…The thin film was mounted on the cartridge of the tensile TEM holder. [26][27][28][29][30][31] Both edges of the sample specimen adhered to the tensile holder with epoxy glue. The cartridge had a $30 μm gap or span length.…”

“…Microcrack growth and void formation in the composite sheets during tensile deformation were observed by real-time transmission electron microscopy (TEM), without staining, and by using a specially designed holder. [26][27][28][29][30][31] Thus, the real-time TEM technique was applied to TEMPO-CNFcontaining rubber composite sheets, for the first time, to make clear the tensile deformation process and mechanism at the nanometer level in term of TEMPO-CNF structures, their clusters, and the rubber/TEMPO-CNF interfaces. The tensile deformation behavior of the two rubber/TEMPO-CNF composites differed a little, because of the different morphologies, sizes, distributions, and structures of the TEMPO-CNF/rubber clusters and TEMPO-CNFs in the composites.…”

Mastering of Filled Rubber Strength beyond WLF: Competition of Temperature, Time, Crack Deflection and Bond Breaking

“…An older, but comprehensive overview about different fracture mechanisms was provided by Gul [16]. Recently, Watanabe et al observed a crack in situ using transmission electron microscopy [17]. The crack progressed in a stick-slip manner by delaminating rubber from the (non-treated) silica surface.…”