Journal of Engineering Science and Technology APRIL 2008, Vol. 31
of nanotubes agglomeration which commonly occurred when it exist in large quantity in the compounding recipes.
Overall the pattern of the plot for the group iv-vi showed very good improvement in their tensile strength properties in comparisons with the un-filled
matrix of PP polymer, where the most significant enhancement of tensile strength was obtained from the group of composites fabricated from CNTs which
compounded at 175°C and 60 rpm which report an increment. The present results for the composites from group vi shows an almost linear increase of the
measured tensile strength value in relation to the filler content, yielding at the maximum of 18.15 MPa at 1.00 wt. MWCNT addition, under the given
processing condition. This finding is in accordance with the previous work conducted by Park et al. [9], where in their study they found that, as CNT content
increased, the tensile strength is increased gradually by the general rule of mixture. They claimed that polymer matrix added with CNT can increase the
tensile properties and fracture energy because the crack propagation can be blunted by bridging up the crack faces [9]. Kueseng et al. [10] found that by
incorporation of CNT even at low as 1.5 filler content, the tensile strength of nanocomposites was enhanced [10].
Application of compounding parameters for the group viii and ix was diminished its tensile strength properties of pure PP matrix, where the values
plotted are lower than 10 MPa. Thus, it can be claimed that the temperature of 185°C with rotor speed of 60 and 80 rpm respectively is not suitable for
MWCNT-PP composites fabrication. High temperature of compounding may expose the molecular chain of PP with the processing degradation, which
generally will decrease its mechanical properties. With the exposure of high shearing rotation of roller rotor blade 80 rpm at 185°C, the effect of high
temperature to the tensile properties of the fabricated composites becomes worst. This phenomenon can be seen at the group ix, where all the plotted values are
among the lowest, where the pattern of plot for this group of composites seems is level with no great improvement in its properties.
Thus, it can be concluded that temperature of compounding and roller rotor speed of melt blending, plays an important roles in the tensile strength properties
of composites which containing lower amount of MWCNT filler loading. Both parameters are mutually correlates between each other and it should be
highlighted as a main consideration during the development and production of carbon nanotubes based polymer nanocomposites in the real bulk manufacturing.
3.2.2 Modulus of Young curves
The Modulus of Young for fabricated composites is depicted as in Fig. 4. Samples were prepared at three different temperatures of various roller rotor
speed of internal mixer, in five different compounding recipes for each group labelled, which varied from 0-1.00wt. of MWCNT addition from total weight
of compounding. Overall, by referring to the control sample matrix of pure PP without addition of MWCNT from each groups of compounding, it can be seen
that the value of Modulus of Young were varied from 113.55 to 200.83 MPa, where the obvious trend of plot shown that, by increasing the rotation speed of the
shearing blade, the pattern of the bar chart plotted were proportionally increased,
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for groups i-iii, monotonically increased for groups iv-vi and drastically decreased for the groups vii-ix. Generally, for each group of compounding,
addition of low amount of MWCNT was increased their value of modulus in comparison with the control sample, but only up to the certain level of amount
before its properties dropped.
However, this is different with the group vii, where the tested value of modulus was dropped when the 0.25wt. MWCNT is added and increased again
until the addition of 0.75wt. MWCNT, before it dropped again at the addition of 1.00wt. MWCNTs. It may due to the failure of compounding parameters
lower speed of roller rotor; 40 rpm; to fully disperse the MWCNT added which may create the formation of MWCNT agglomerates that tend to be the origin of
flaw which may create failure, during the testing. The increment of modulus of young properties was not significantly occurred at the group i-iii, where the
temperature used is 165°C. The effect of roller rotor speed in this phase was not too obvious where the plot of the graph seems to be level. Great improvement of
this property was occurred for all group of compounding in the second phase of the bar chart plotted groups iv-vi and only at the group vii and viii for the
third phase of the graph. Highest increment of this property was occurred at the group viii, where addition of only 0.75wt. MWCNT, contributed to the
enhancement of Modulus of Young value up to the 162.3.
50 100
150 200
250 300
350 400
i ii
iii iv
v vi
vii viii
ix
Compounding Parameters M
od ul
us of
Y o
ung M
P a
0wt. MWCNT 0.25wt. MWCNT
0.50wt. MWCNT 0.75wt. MWCNT
1.00wt. MWCNT 165°C
175°C 185°C
Fig.4. Modulus of Young of PP-MWCNTs Composites Compounded at 165- 185°C at Various Roller Rotor Speed of Internal Mixer.
Kueseng et al. [10] found that the dispersion of nanoparticles in the polymer matrix used, gives rise to the increase in modulus. The increased stiffness may be
caused by the formation of the immobilised matrix phases due to the incorporation of the nanotubes or nanoparticles [10]. The increment of modulus
values with increasing the amount of filler loading was in agreement with what was reported by Girun et al. [7], where in high CNTs loading the nanocomposites
are able to withstand more loads. The fabricated composites become stiffer. Maximum value plotted for this property occurred when the compounding using
175°C of compounding temperature at 60 rpm of rotor speed with the addition of
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0.75 wt. MWCNT was applied, where it improved the modulus of young value up to 128 in comparison with the pure PP which compounded at the same
parameter of compounding. Generally, using temperature of 185°C with high roller rotor speed of 80 rpm
gives the value of modulus among the lowest compared to others. Again, it is revealed that this compounding parameter group ix, is totally not suitable for
the MWCNTs-PP nanocomposites fabrication. However, using this temperature but lowering the speed of shearing blade, still capable to give promising result of
improvement in its properties for Modulus of Young.
3.2.3 Percentages of elongation at break curves
