cotton - Greenmount Press

FIGuRE 3: Polyester thermoset composites.
s Reclaimed fibre reinforced composite.
u Virgin natural fibre reinforced composites
from published literature.
FIGuRE 4: Polypropylene thermoplastic
composites. l unreinforced polypropylene
plastic. s Reclaimed fibre reinforced composite.
u Virgin natural fibre reinforced composites
from published literature.
thermoplastic polymer matrices in which fibres can be set to
make a composite product. In this preliminary study, we used:
■ Unsaturated polyester (thermosetting resin type F61347 from
Fibre Glass International); and,
■ Polypropylene (thermoplastic fibre supplied by a local textile
factory) matrices.
■ The decision on which matrix to use is based on cost and
performance. The reclaimed textile fibre used in the study was
supplied from a textile fibre recycling factory in Victoria.
Two important performance criteria for engineering materials are
strength to break and stiffness (elastic modulus). These properties
may be tested by a tensile test or a flexural test.
Test results
Thermoset composite
The reclaimed textile fibre was opened and converted
into a lapped mat on a mini carding machine. The mat was
consolidated on a laboratory needle-punching machine. The
unsaturated polyester resin was applied to the material which
was then cured at room temperature while being held in a press
set to a five-tonne constant pressure. The resulting composite
sample was 3.12 mm in thickness with a density of 1.33 g/cm 3 .
The fibre:resin ratio in the final composite was 56:44.
The final composite sample showed a flexural strength of 55
MPa and an elastic modulus of 4.2 GPa. When compared with
published results of composite materials made from virgin natural
fibre mats, we find that the composite made from reclaimed
fibres was within the range, albeit sitting at the lower end, as
shown in Figure 3. Considering the lower material cost and other
potential benefits, it is still a worthwhile alternative to consider.
Thermoplastic composite
The reclaimed textile fibre was blended with the polypropylene
fibre at 50:50 weight ratio. The blended material was carded and
needle-punched to produce a consolidated mat (the preform).
The preform was cut to rectangular swatches according to the
size of the mould.
The swatches were stacked in the mould and placed in a hot
press. The two heated platens on the hot press were closed and
the temperature was raised to 190°C that was maintained for
20 min before the heating elements were switched off to let the
sample cool down. A constant pressure of 0.5 MPa was applied
throughout the process.
The thermoplastic composite material from reclaimed fibres
showed much better mechanical properties (strength 78MPa
and modulus 7.2 GPa) than the thermosett composite. The
mechanical properties of the final composites are compared with
published results of thermoplastic composites made from virgin
natural fibre mats in Figure 4. The composite from reclaimed
fibres was one of composites with the best combined mechanical
properties.
In summary, we converted recycled fibres into thermosett
and thermoplastic polymeric composites and evaluated their
mechanical performance. The composites reinforced by the
recycled fibres show similar mechanical properties as those
reinforced by virgin plant fibres such as hemp, flax and jute
that are being increasingly used as automotive parts, furniture,
building and packaging materials.
1
CSIRO Materials, Science and Engineering Division, Belmont, Victoria 3216.
Emails: Menghe.Miao@csiro.au, Stuart.Gordon@csiro.au
40 — The Australian Cottongrower December 2012–January 2013