To correlate the influence of fibers hemp content on the
mechanical properties and rubber–fiber interactions, the
morphological aspect of the natural rubber/hemp composites
was necessary to be evaluated by SEM technique. For
SEM analysis, the samples were initially immersed in solvent
(toluene and xylene) for 72 h to remove unvulcanized
natural rubber. SEM micrographs of the natural rubber and
natural rubber/hemp composites with 10 and 20 phr hemp
content are shown in Figs. 6, 7 and 8.
Fiber alignment factors play a crucial role in the overall
properties of composites. There is always a chance of fiber
entanglement with randomly oriented fibers reinforced
composites. The random orientation of fibers produces
lower mechanical properties compared to long unidirectionally
oriented fibrers. This fiber entanglement can create
elastomeric rich areas, which can contribute to the formation
of voids and porosity. Voids and porosity can act as
stress concentrators leading to failure of composite samples
[53]. The SEM micrographs obtained showed fibers dispersion
within the matrix.
Figures 7 and 8 indicate that the hemp fibers present
striations, parallel to the fiber axis. The SEM micrographs
also revealed that the hemp fibers are uniformly distributed
in the natural rubber matrix. This distribution plays a
positive role in improving the properties of the composite,
especially the tensile strength, as observed in this study.
Also, it is observed that with the increase of hemp amount
in composites, fibers appear not individually but forming
large bundles. Micrographs also show the effect of the
fracture on the fibers.