Structural–mechanical properties
of surface defects in NR
vulcanizates in undeformed and stretched states including static cracks
are studied by atomic force microscopy. Elastoplastic microdefects
(cracks and strands) are observed on the undeformed surface at certain
sample cutting conditions. In the stretched materials, matrix detachment
is found at the poles of inclusions but the propagation of such longitudinal
nanocracks is hampered by inclusions and cross-linking heterogeneities.
The elastic modulus within these detachments is 2 times higher the
matrix. The properties of other defects–transverse cracks in
the stretched rubber depend on filler concentration and distance from
the crack tip. Such cracks are covered by polymer strands (thickness
∼20 nm) and a network of nanofibrils (∼1 nm). The measured
modulus near the crack tip reaches 1 GPa and reduces to 200 MPa at
the end. The observed features are related to the strain induced crystallization
and high local extension of NR.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.