increases with increasing fiber loading in both as-received and
treated UHMWPE fibers/NR composites. Higher amounts of fibers
are found to give higher hardness. Compared with pure NR, the
hardness of as-received and treated UHMWPE fibers/NR composites
is increased to 94% and 88%. However, the difference between
as-received and treated UHMWPE fibers/NR composites added the
same fiber content is not obvious.
3.2.4. Dynamic mechanical properties of UHMWPE fibers/NR
composites
The dynamic mechanical properties of NR and UHMWPE fibers/
NR composites were also performed. The variation of storage
modulus (E0) and tangent delta (tan d) as a function of temperature
are reported in Figs. 8 and 9. The dynamic properties reflect the
amount of the energy in the composite stored as elastic energy and
the amount of energy dissipated during the strain process. These
properties are highly dependent on the existence of fillers:
dispersion within the matrix, volume fraction, geometrical characteristics,
and load transfer from the filler to the matrix [24]. As
illustrated in Fig. 8, at low temperatures, NR was in the glassy state
and its storage modulus remained roughly constant at 1.5 GPa. This
was due to the fact that in the glassy state, the molecular motions
were largely restricted to vibration and short-range rotational
motions. The glassy modulus are 1.9 and 0.5 GPa with the addition
of as-received and treated UHMWPE fibers, respectively. It is
remarkable that the as-received UHMWPE fibers/NR composites
gives the highest energy dissipation in the temperature region over
the glass transition temperature. This can be attributed to the very
weak fiber/polymer bond in the composite [25]. As-received
UHMWPE fibers/NR composites give an increase in E0 in both the
rubbery region and glassy region, treated UHMWPE fibers/NR
composites only in the rubbery region. For instance, at 40 C the