The objective of this research was

The objective of this research was to obtain a new elastomeric
material based on NR, with enhanced properties, by
replacing active fillers from rubber blends such as carbon
black or silica with natural hemp fibers. The values of hardness,
tensile strength and tearing strength have increased
with the fiber content increasing in the composite due to
a good interaction of fiber with NR and these results indicate
that hemp has a reinforcing effect on natural rubber.
The gel fraction value was over 95 % for all blends and
increased with the amount of hemp in the composites. The
cross-linking density (ν) of samples changed slightly as the
amount of hemp in blends increased. It can be observed
that water uptake increased with increasing fiber content
and temperature because the diffusion of water in elastomers
was not straightforward by the presence of hydrophilic
materials (such as the hemp). The water absorption
tests indicate that for the temperature of 23 ± 2 °C the saturation
appeared after 456 h for the sample without hemp
and after 600 h for sample containing hemp, while the
high temperature of 70 °C seems to accelerated the water
uptake behavior and the saturation appeared after 216 h
for the sample without hemp and after 264 h for sample
with hemp. To investigate the reinforcement efficiency of
natural fibers, the infrared spectra of natural rubber, hemp
fibers and natural rubber/hemp fiber composites vulcanized
with sulfur have been achieved in the 4,000–650 cm−1
range. The main components of natural fibers (cellulose,
hemicellulose, and lignin), NR-specific proteins and fatty
acid ester groups and the amide groups produced by the
accelerated sulfur curing systems were identified in the
investigated mixture. Also, to correlate the influence of fibers
hemp content on the mechanical properties and rubberfiber
interaction, the morphological aspect of the natural
rubber/hemp composites was evaluated by SEM technique.
The micrographs obtained showed the fiber dispersion
within the matrix and a good adhesion of fibers with the
matrix. SEM micrographs also revealed that the hemp fibers
are uniformly distributed in the natural rubber matrix,
fact which plays a very important role in improving the
properties of the composite, especially the tensile strength.
Our investigations concerning the basic mechanical properties,
some physical and chemical parameters, the infrared
spectroscopy and scanning by electron microscopy depending
on hemp content in NR vulcanized with sulfur proved
the reinforcing effect of the hemp fibers.

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