Materials Sciences and Applicatio ns, 2011, 2, 1331-1339
doi:10.4236/msa.2011.29181 Published Online September 2011 (http://www.SciRP.org/journal/msa)
1331
Printability of HDPE/Natural Fiber Composites
with High Content of Cellulosic Industrial Waste
Luis Claudio Mendes*, Sibele Piedade Cestari
Institute of Macromolecules Professor Eloisa Mano, Federal University of Rio de Janeiro, Centro de Tecnologia, Bloco J, Avenida
Horácio Macedo, Rio de Janeiro, RJ, Brazil.
Received June 1st, 2011; revised June 17th, 2011; accepted June 22nd, 2011.
ABSTRACT
In this paper, a continuous polymeric matrix highly filled with fiber of sugarcane bagasse has been obtained and its
feasibility as an ink-absorbing material has been eva luated. In order to study the effect of the amount of cellulose fiber
on the surface printability, contact angle measurement using different liquids—water-based inks, ethanol and ink for
ink-jet printers—and printing tests were performed on composites of high density polyethylene (HDPE) and sugarcane
bagasse (SCB). The composites were processed in a Haake internal mixer, using the SCB without any previous chemi-
cal treatment or compatibilizer. The differential scanning calorimetry (DSC) and derivative thermogravimetry (TG/
DTG) revealed an increase in the thermal stab ility and in the degree of crystallinity of th e HDPE. The optical micros-
copy (OM) and scanning electron microscopy (SEM) showed that the cellulosic material was homogeneously embedded
within the HDPE matrix. In order to assess the resistance of the composite sample to the pull strength of the printer,
tensile tests were applied to the composites and th e results were compared to known paper samples. The best result was
achieved in the composite with the highest content of SCB, as well as the shortest drying time.
Keywords: Recycling, Composite, Printing Properties, HDPE, Sugarcane Bagasse
1. Introduction
Nowadays one of the major concerns of society is to
preserve natural resources, because the awareness of its
finitude. The search for sustainable solutions is visible in
all sectors of economy [1]. Even raw materials from re-
newable font must have its levels of use reduced, since
they make use of finite natural resources (fertilizers, wa-
ter).
The use of polymeric materials has reduced the con-
sumption of finite natural resources in many industrial
applications [2]. The cellulose industry plays an important
role in these sustainability matters, and is a sector of the
productive chain that can be benefited by the use of
polymeric materials. The use of thermoplastics in some
commodities can reduce the necessary volume of cellu-
lose in its composition, and even replace some established
products—as paper, for instance, which already has a
synthetic substitute for some printing applications.
Composite materials like plastic lumber [3], wood-
plastic composites [4] and natural fiber reinforced com-
posites [5] were developed intending to achieve more
sustainable solutions for the construction and reinforced
plastics market. The proposition is, through the applica-
tion of recycled plastics as raw material (raising its life-
cycle and reducing its disposal in the environment), and
using renewable-source reinforcing fillers, elaborate eco-
friendly materials with wide application (as substitutes for
some wood and automotive products). Cui et al. [6]
studied the properties of wood fiber-reinforced recycled
plastic composites manufactured from sawdust and post-
consumer HDPE. It was observed that the incorporation of
wood fibers results in higher melting and slower crystal-
lization rate of the composites. Also its thermal and me-
chanical properties varied significantly according to plas-
tic content, length of wood fiber and compatibilizer con-
tent of the composites.
Most of the existing plastic lumbers use recycled plas-
tics only. Martins et al. [7], when studying mechanical
properties of IMAWOOD® plastic lumber, inform its
composition: LDPE/HDPE 3:1 blend, obtained from post-
consumed plastic bags recovered from municipal dump.
But they are designed to work mainly as structural parts,
and its success as a commoditie is attached to the effi-

Printability of HDPE/Natural Fiber Composites with High Content of Cellulosic Industrial Waste
1332
ciency of the plastic waste selective collection.
The wood-plastic composites (WPC) have actually
substituted some wood products (the medium density
fiberboard—MDF—has overcome the traditional ply-
wood boards in the Brazilian furniture market), but many
compatibilizers and fiber treatments must be used in order
to achieve the strong mechanical properties they need [8,
9]. And natural fiber reinforced composites (NFRC) in-
tend to substitute inorganic for natural fiber reinforcing
fillers [10], aiming to improve the properties of the neat
polymer [11]. Singh et al. [12] developed jute fiber rein-
forced phenolic composite profiles as an alternative to
wooden frames in buildings, intending to develop com-
posites for structural applications. Most studies in the
polyolefin/natural fibers composites area chemically
treats the cellulosic fibers, to improve its adhesion and/or
to bleach the fibers. Gwon et al. [13] studied the modify-
cation of wood fibers using alkali treatment and coupling
agent reactions, mixed with polypropylene resin, con-
cluding that the fiber treatments increased physical pro-
perties due to the introduction of compatible molecular
structure onto the wood fiber surfaces.
None of these cited composites—plastic lumber, WPC
and NFRC—have been elaborated just to gather the cel-
lulosic filler with polymer, neither dealing with poor ad-
hesion between polymer and filler, nor aiming to improve
mechanical properties. But the development of such ma-
terial would be an interesting application to cellulosic
filler in a polymeric composite, and could lead to a sus-
tainable material for the printing industry, and reduce the
consumption of cellulosic pulp in several know applica-
tions.
Therefore, the idea of this work is to create a sustain-
able material making use of the polarity of cellulose as
vehicle for receiving and retaining ink, in order to obtain
a continuous polymeric matrix highly filled with fiber of
sugarcane bagasse and to evaluate its feasibility as an
ink-absorbing material. The goal of the experiment was
to achieve simple blends, with few components.
As this work focus on the environmental aspects of the
experiment, it was decided not to bleach the SCB fibers,
to preserve its natural polarity and to avoid the genera-
tion of pollutant effluents (chlorine and hydrogen pero-
xide based). At first, the idea was to use recycled HDPE,
but the difficulties in dealing with a heterogeneous mate-
rial, associated with raw filler, lead to the use of virgin
HDPE instead of the recycled polymer.
2. Experimental
2.1. Materials
The materials were high density polyethylene (HDPE)
named Petrochem HC 7260—density equal 0.958 g·cm−3;
melt flow rate (MFR) equal 8g·10 min−1—supplied by
Ipiranga Petroquímica, and sugarcane bagasse (SCB)
waste from HC Sucroquímica sugarcane plant (Campos
dos Goytacazes, RJ, Brasil).
The latter was used without any previous chemical
treatment, and then grinded and sifted using a sieve with
40 mesh, according to the ISO 3301. The SCB fiber that
passed through the sieve was used in the composite. Be-
fore the composite preparation, both materials were dried
in an oven, at 105˚C, for 2 hours.
2.2. Composite and Specimen Preparation
Composites of HDPE/SCB were prepared varying the
SCB content from 0 to 70 wt%—named 100/0, 80/20,
50/50 and 30/70—in a Haake internal mixer, at 180˚C,
60 rpm, for 10 minutes. After that, the material was com-
pression molded as a plate of 1 mm thickness, in a hy-
draulic press at 200˚C, 10,000 psi, for 5 minutes, being
subsequently cooled in another hydraulic press, at 25˚C,
430 psi, for 5 minutes.
2.3. Optical Microscopy and SEM Analysis
The morphology of the materials was noticed by usual
techniques. Optical microscopy (OM) observation was
performed with an Olympus stereo microscope, model
SZH10, equipped with a Nikkon Coolpix 5400 digital
camera attached.
Triturated SCB, processed HDPE and the three com-
posites were analyzed. Scanning electron microscopy
(SEM) was performed using a Fei Company microscope
model Quanta 200, using specimens coated with 300 nm
gold particles (Au) applied by JEOL equipment model
JFC 1500. Cryogenically fractured transversal sections
and surfaces of the samples were assessed.
2.4. Differential Scanning Calorimeter (DSC)
The differential scanning calorimetry (DSC) was done
using a TA equipment model TA Q1000. Three thermal
cycles were performed. In first one, the sample was
heated from 0˚C to 200˚C, at heating rate of 10˚C·min−1,
under nitrogen atmosphere. In order to eliminate the
thermal history, it was left at 200˚C for 2 minutes. The
second one was a cooling cycle from 200˚C up to 0˚C, at
10˚C·min−1. At the third cycle, the same temperature
range and heating rate of the first cycle were applied.
The crystalline melting temperature (Tm) and the de-
gree of crystallinity (Xc) of the HDPE were obtained
considering the second heating cycle curves. The Xc was
determined based on the ratio between the ∆H of the
HDPE in the composite and the ∆H of the 100% crystal-
line HDPE (290 J/g), adjusted according to the percent-
age of the polyolefin in the composite.

Printability of HDPE/Natural Fiber Composites with High Content of Cellulosic Industrial Waste1333
2.5. Thermogravimetry
Thermogravimetry/derivative thermogravimetry (TG/DTG)
was performed in a TA model Q500 equipment, from
30˚C to 700˚C, at heating ratio of 10˚C·min−1, in a nitrogen
atmosphere. The weight loss, initial and final degradation
temperatures—Tonset, Tfinal respectively—were evaluated.
2.6. Contact Angle
The measurement of contact angle was performed in a
Ramé-Hart N.R.L goniometer, model 100 - 00, using RHI
2001 Imaging Software. It measures the angle between a
plane tangent to a drop of liquid over a solid surface, and
the plane of this surface. Four liquids were used: distilled
water (DW), ethanol (EOH), mixture DW/EOH and ink-
jet ink (IJI).
2.7. Printing Test
Printing tests were done using a Cannon printer, model
MP 160. Samples of 110 × 110 × 0.5 mm of each com-
posite were attached to a sheet of A4 paper. Text, color
and black-and-white drawings were printed onto the
composites surface, and pictures were taken after the
drying time. The photographs were taken with a Canon
EOS XT 350D digital camera, 35 - 80 mm lens.
2.8. Tensile-Strain Test
The tensile test was performed in an Instron tester model
5569, according to the ASTM D 882, using a load cell of
10 kN, test speed of 25 mm/min., and rectangular speci-
men of 10 × 100 mm. The test was also carried out over
known paper samples (board and kraft), to compare the
results. The Young modulus, the stress and elongation at
yield, the stress and elongation at break were evaluated.
The results consider the mean of 5 specimens of each
sample.
3. Results and Discussion
The distribution of fiber length revealed that 77% of the
ground SCB has passed through the 20 mesh sieve. In
this fraction, the higher portion—36%—passed through
the 100 mesh sieve. Since smaller fibers present a better
dispersion into the polymeric matrix, it was decided to
use all the material that passed through the 40 mesh sieve
(around 1 mm to lower fiber lengths), corresponding to
66% of the triturated SCB. The ratios between fines/
HDPE percentages in the composites were calculated, in
order to evaluate the influence of the fines in the proper-
ties of the composites –0.14 for the 80 - 20, 0.55 for the
50 - 50 and 1.28 for the 30 - 70 composite.
3.1. Optical Microscopy and SEM Analysis
The OM and SEM photomicrographies of the composites
(Figures 1-2) revealed fine dispersion between polymer
and filler. Comparing the particle size of the triturated
filler to those of the composites shows that some shearing
occurred during the processing in the Haake mixer.
The good interaction between the two materials may
have come from the variety of sizes of the ground SCB
particles, which included a lot of fines. Also the presence
of lignin may have worked as a compatibilizing agent in
the composites, as seen in some studies [4,14]. The SEM
revealed that the SCB particles were completely encap-
sulated by the HDPE, even in the 30 - 70 composite. It
also confirms fine dispersion between the materials.
3.2. Differential Scanning Calorimetry
The DSC curves are shown in Figure 3, and the results
of the composites and its parent materials are in Table 1.
The SCB curve presented an intense peak at the first
heating cycle—between 50˚C - 170˚C (maximum value
was around 120˚C), ascribed to the loss of moisture—
which disappeared in the second heating cycle. For the
composites, considering the second heating cycle, no
variation was observed in the Tm of the HDPE (132˚C),
denoting that the average size of the crystals did not
change. At all the heating cycles, there was a raise in the
Xc depending on the content of SCB in the composites.
Figure 1. OM photomicrographies of the materials: (a)
ground SCB, (b) 80 - 20 composite, (c) 50 - 50 composite
and (d) 30 - 70 composite.
Table 1. Melting temperature and degree of crystallinity of
the composites.
HDPE/SCB composite Tm (˚C) Tc (˚C) Xc (%)
100 - 0 132 120 66
80 - 20 132 119 84
50 - 50 132 121 68
30 - 70 132 120 83

Printability of HDPE/Natural Fiber Composites with High Content of Cellulosic Industrial Waste
1334
Figure 2. SEM photomicrographies of the materials: 80 - 20 composite (a) section and (d) surface, 50 - 50 composite (b) sec-
tion and (e) surface, and 30 - 70 composite (c) section and (f) surface.

Printability of HDPE/Natural Fiber Composites with High Content of Cellulosic Industrial Waste1335
(a) (b)
(c) (d)
Figure 3. DSC curves of the materials: (a) SCB, (b) 80 - 20 composite, (c) 50 - 50 composite and (d) 30 - 70 composite.
This increase in the Xc, associated with no variation in
the Tc, may be due to some transcrystallization. Com-
monly, after melting, the bulk molten of a semicrystalline
polymer can recrystallize under cooling. It takes place
under homogeneous nucleation, and where the amount of
the crystalline portion has the same order of magnitude
as the initial material. Concerning to the composites,
transcrystallization is a special case of crystallization
where a heterogeneous nucleation is feasible along a fi-
ber surface. The transcrystallization is a function of nu-
cleating activity of the fiber surface and crystallization
kinetics of the resin matrix [15]. Also, this phenomenon
was described by Na et al. [16], when performing mor-
phological investigations of an isotactic polypropylene
matrix induced by synthetic fibres.
3.3. Thermogravimetry
Table 2 lists the initial and final degradation tempera-
tures (Tonset and Tfinal, respectively), the maximum deg-
radation temperature (Tmax) and the amount of remaining
residue of the parent materials and the composites. The
HDPE curve (Figure 4(a)), as expected, showed a single
step degradation, and the entire sample burned, leaving
no residue. The SCB and 30/70 composite curves are
shown in Figures 4(b) and 4(e). The SCB presented
three different steps of weight loss. The first one is pro-
bably due to loss of moisture. At the second stage, the
ascending part of the derivative thermogravimetry (DTG)
curve presented a shoulder and a peak—highlighted in a
Table 2. Tonset, Tfinal and Tmax of the materials.
HDPE/SCB
Composite Tonset (˚C) Tfinal (˚C) Tmáx (˚C) Residue (%)
100/0 433 500 461 -
80/20 307/459500 354/478 -
50/50 303/444550 349/472 3
30/70 258/448550 295/351/472 10
SCB 292 575 344/496 2

Printability of HDPE/Natural Fiber Composites with High Content of Cellulosic Industrial Waste
1336
(a) (b)
(c) (d)
(e)
Figure 4. TG/DTG degradation curves of the materials: (a) HDPR, (b) SCB, (c) 8 0 - 20 composite and (d) 50 - 50 composite;
(e) 30 - 70 composite.
dot circle—ascribed to the burn of hemicellulose and
cellulose, respectively. And the third step was attributed
to the degradation of lignin.
The weight loss curves of the composites showed burn
steps similar to the parent materials. There was mutual
influence in the thermal parameters considered in this
study. The Tonset, Tfinal and Tmax temperatures of the HDPE
were shifted to higher values, indicating a raise in its
thermal stability due to the presence of the SCB.
Concerning to the 30 - 70 composite, there was a
change in the burn profile of the SCB. What first seem to
be a shoulder and a peak on the SCB thermogram, turned

Printability of HDPE/Natural Fiber Composites with High Content of Cellulosic Industrial Waste1337
into two well-defined peaks (Tmax = 295 and 351˚C). The
amount of residue increased as the content of SCB in the
composite raised.
3.4. Contact Angle
Contact angle test results for the four liquids (DW, EOH,
DW/EOH and IJI) are shown in Table 3. Figure 5 gra-
phically shows an overall comparison. The composites
presented high repellency to DW (water). The 100 - 0
composite presented nearly no variation to the three other
liquids. The addition of 20%, 50% and 70% of SCB in-
fluenced the results for EOH, DW/EOH and IJI contact
angles.
Concerning to DW/EOH and IJI contact angle values,
the composites showed a similar behavior. For EOH, there
is a linear decrease of the contact angle depending on the
SCB content. The results clearly show that the increase of
the SCB content in the composites raises the absorption
efficiency of the tested liquids.
3.5. Printing Test
The composite sheets were cleaned with ethyl alcohol
before being printed, having no other surface treatment.
The printing tests (Figure 6, Online Resource 1) showed
the composites’ capability of absorbing inkjet ink. It took
from 6 to 24 hours for the ink to completely dry on the
other composites, and the 80 - 20 composite was unable
to retain it at all.
Observing the 80 - 20 and 50 - 50 printing tests, one
can see the ink had formed drops that did not spread on
the sheet surface, resulting in a blurred, non-graphic
quality, which was easily smudged. On the 30 - 70 com-
posite the ink was completely dried and partially ab-
sorbed within a reasonable time (about 1 hour). The
quality of the printing improved as the cellulose content
in the composite raised.
3.6. Tensile-Strain Test
The tensile test provided by the Young modulus, tensile
stress at maximum load, tensile strain at maximum load,
stress at break and strain at break, and the results are
shown in Table 4. The Young modulus decreases with
lower amounts of SCB filler, but for the 50 - 50 and 30 -
70 composites it reaches a value close to neat HDPE. The
increase of the amount of filler decreases the tensile
stress, tensile strain, break strength and break elongation
values, as seen by Mulinari et al. [17] when studying
sugarcane bagasse/HDPE composites obtained by extru-
sion. The moduli of the plastic materials are inferior to
those of commercial paper, but the elongation of the 80 -
20 composite is similar.
4. Conclusions
These results show that the association of triturated SCB
with a polymeric matrix brings up fine results in terms of
printability, thermal and mechanical properties. In ge-
neral, the developed materials seem to fit the purpose of
aggregating cellulosic industrial waste using a polyole-
Table 3. Contact angles for the materials.
Liquids
Composite HDPE/SCB DI water Ethanol DI water/ethanol mix 50 - 50% Inkjet ink
100 - 0 75 ± 13 23 ± 7 23 ± 7 20 ± 4
80 - 20 61 ± 12 20 ± 2 37 ± 4 25 ± 5
50 - 50 71 ± 11 12 ± 4 46 ± 4 31 ± 6
30 - 70 77 ± 12 8 ± 3 42 ± 8 26 ± 7
Table 4. Tensile parameters.
Material Young modulus
(MPa) Stress at Maximum Load (MPa) Elongation at Maximum Load (%) Stress at break (MPa) Elongation at break (%)
HDPE 590 ± 54 24.1 ± 1.6 14.1 ± 1.7 19.3 ± 1.3 24.2 ± 8.0
80% - 20% 356 ± 19 7.7 ± 0.8 3.1 ± 0.4 6.1 ± 0.6 3.6 ± 0.5
50% - 50% 512 ± 128 4.4 ± 1.7 1.2 ± 0.3 3.5 ± 1.4 1.4 ± 0.3
30% - 70% 588 ± 133 3.0 ± 0.8 0.9 ± 0.1 2.4 ± 0.6 1.0 ± 0.1
Board paper 1568 ± 87 22.6 ± 1.1 2.6 ± 0.2 22.4 ± 1.0 2.6 ± 0.2
Kraft paper 2218 ± 195 67.1 ± 4.3 4.5 ± 0.2 66.4 ± 4.2 4.5 ± 0.2

Printability of HDPE/Natural Fiber Composites with High Content of Cellulosic Industrial Waste
1338
Figure 5. Comparative graphic contact angle x solids.
Figure 6. Printing test of the composites: (a) 80 - 20 com-
posite, (b) 50 - 50 composite and (c) 30 - 70 composite.
finic matrix, in order to create a printing surface through
a simple, low cost and eco-friendly composite.
5. Acknowledgements
The authors thank to the Conselho Nacional de Desen-
volvimento Científico e Tecnológico (CNPq) and to the
Fundação Coordenação do Aperfeiçoamento de Pessoal
de Nível Superior (CAPES), and to the Nosso Futuro
Comum blog community headed by the economist Hugo
Penteado, for supporting this investigation.
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