الفهرس 
Polymer Matrix CompositesOnly 14 pages are availabe for public view
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Abstract
This study investigates a novel technique for the fabrication of well dispersed
carbon particle reinforced polymer composites. The technique is based on the
in-situ generation of the particles during polymer melt processing through the
incorporation of a carbon-rich precursor of low thermal stability. During
processing, the precursor is decomposed, leaving behind carbonaceous char
within the polymer matrix.
The potential of reinforcing polypropylene (PP) with carbon particles through
the above described in-situ process is proven. In this study 44 µm
reinforcement carbon particles are created through pyrolysis of
carboxymethylcellulose (CMC) at a processing temperature of 270 °C.
Five different concentrations (2.5, 5, 10, 15, 25 wt%) of CMC powder were
mixed with polypropylene and pyrolysed through successive extrusion
compounding cycles, before being injection moulded.
CMC is a soluble polysaccharide with a wide application in food and
biomedical applications. Studies report the pyrolysis of CMC at high
temperatures beyond 400 °C to obtain activated carbon for use in pollution
treatment, and biomass gasification. In contrast, this study noticed, amongst
other aspects, low temperature pyrolysis ranging between 260 and 300 °C
producing micro sized carbon suitable for further use as filler material in PP
based composites.
Necessary pyrolysis and processing conditions were defined through
preliminary thermal analysis of PP and CMC using isothermal and dynamic
Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry
(DSC) methods. Observations reveal that a minimum holding temperature of
260 °C is required for pyrolysis, at which the process is terminated after
II | P a g e
around 26 minutes. Increasing exposure temperature reduces pyrolysis time.
Resulting char was analysed using X-ray Diffraction (XRD), Fourier
transform infrared spectroscopy (FT-IR) and Visual inspection using scanning
electron microscopy (SEM). CMC char particles were found to be composed
of functionalized amorphous carbon of spherical shape, having an average
particle size of 44 µm, which is applicable for composite filling purposes.
Pyrolysing CMC during polymer processing resulted into well dispersed
carbon particle filled polypropylene composites without any agglomerations,
as evidenced by scanning electron microscopy (SEM). Thermogravimetric
analysis of these composites reveal a carbon content of 4 - 28 wt.% when
initially mixing 2.5 - 25 wt.% CMC into the PP. Mechanical testing of the
carbon reinforced PP results in an improvement in impact strength by 69%,
however, at the cost of a 14% DROP in tensile strength, both associated with a
weak particle-matrix interface as evidenced by SEM and mathematical
modelling of the interface. This, in addition to the prolonged processing time
are outcomes calling for the optimisation of the compounding and pyrolysis
process in future work. However, this study definitely shows the potential of
reinforcing thermoplastic polymers through the pyrolysis of another carbonrich polymer of low thermal stability.
Finally, this work relates the mechanical behaviour of the in-situ composites
under investigation to the chemistry and morphology of the composite
structure and the interfacial characteristics between particles and matrix. The
interfacial strength was modelled and correlated with the findings of SEM
analysis.