i An update to this article is included at the end

Polymer Testing 24 (2005) 474–482

www.elsevier.com/locate/polytest
Material Characterisation
A comprehensive characterization of chemically treated Brazilian
sponge-gourds (Luffa cylindrica)
Valcineide O.A. Tanobea, Thais H.D. Sydenstrickera,1, Marilda Munarob,
Sandro C. Amicoa,*
a
Mechanical Engineering Department, Federal University of Parana, P.O. Box 19011, 81531 990, Curitiba PR, Brazil
b
Institute for the Development of Technology, LACTEC, Curitiba, PR, Brazil

Received 24 October 2004; accepted 29 December 2004

Abstract
Sponge-gourds, the fruit of Luffa cylindrica, are widely used throughout the world. Despite that, there is lack of scientific data
concerning thermal, mechanical, and chemical properties of these fibers. Sponge-gourds biocomposites are a novel use of these
fibers, but a better understanding of their surface characteristics is necessary to maximize their potential use. In this work,
different chemical treatments were conducted on the fibers with aqueous solutions of NaOH 2%, or methacrylamide (1–3%) at
distinct treatment times. L. cylindrica was characterized via chemical analysis and analytic techniques such as FTIR,
XPS/ESCA, X-Ray, TGA and SEM. Methacrylamide 3% treatment for all times (60, 120 or 180 min) severely damaged the
fibers. NaOH, on the other hand, showed the same beneficial effect regarding enhancement of surface area and thermal stability
together with similar levels of lignin and hemicellulose extraction, without causing exaggerated harm to fiber integrity.
q 2005 Elsevier Ltd. All rights reserved.

Keywords: Luffa cylindrica; Fibers; Chemical treatment; Characterization and composites

1. Introduction composed of fibrils glued together with natural resinous

materials of the plant tissue [1–3]. Whilst some fibers have
Vegetable fibers are spread worldwide, as a renewable been extensively investigated and used in textile fabrics,
resource material mainly abundant in the tropics. Their composites, and for medical purposes, many other less
biodegradability can contribute to a healthier ecosystem and known fibers find limited applications, for instance, in
their low cost and reasonable performance fulfill economic making ropes, mats, purses and wall hangings. One of the
interests of various industries. handicaps for finding new uses for these natural fibers is the
Natural fibers, from leaves, seed or bast include coir, lack of available scientific data regarding their structure and
sisal, jute, sponge-gourd (Luffa cylindrica), flax, ramie, properties. Natural fibers have little resistance towards
abaca, kenaf, cotton, palmyra, bamboo, mesta, henequen, environmental influences and show an intrinsic variability
istle, kapok, hemp, sunn, piassava, wood, banana, kusha, of their properties. Hence, the use of natural fibers depends
sawai grasses, pineapple, etc. These materials are all on the environmental conditions which are likely to
influence aging and degradation effects [4].
The use of different kinds of physical or chemical surface
* Corresponding author.
treatment such as corona discharge or reaction with alkyl
E-mail addresses: valci@demec.ufpr.br (V.O.A. Tanobe),
thais@demec.ufpr.br (T.H.D. Sydenstricker), marilda@lactec. ketone dimers, alkalis, silane-coupling agents, etc. leads to
org.br (M. Munaro), amico@ufpr.br (S.C. Amico). changes in the fiber surface structure as well as to changes in
1
Tel.: C55 41 361 3430; fax: C55 41 361 3129. their surface energy. When cellulose reacts with alkyl

0142-9418/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.polymertesting.2004.12.004
 V.O.A. Tanobe et al. / Polymer Testing 24 (2005) 474–482 475

ketone dimer, for instance, there is a reduction of the

interfacial free energy. An old method of cellulose fiber
modification is mercerization, an alkali treatment that, in
optimal conditions, ensures the improvement of the tensile
properties and absorption characteristics [5].
Although L. cylindrica is commonly found in China,
Japan and other countries in Asia and Central and South
America, the absence of a thorough study of its character-
istics and properties in the technical literature turns this fiber
into an exotic material. Many works on the effect of nitrogen
and phosphorus on fruit yield and quality of sponge-gourd
[6], on L. cylindrica production practices [7,8] and on
genetic diversity in cucurbits [7] are available. However,
apart from the plant [9] and seed characterization [10,11],
little has been done concerning L. cylindrica characteriz- Fig. 2. L. cylindrica varieties.
ation and its modification by chemical treatments.
The fruit of the sponge-gourd (L. cylindrica) plant which bath sponges, the small sponge-gourd variety (acutangula) is
is of the Curcubitacea family [12] is shown in Fig. 1(a). The used for medical purposes in sinus conditions and as beds to
ripe fruit shown in Fig. 1(b) has a thick peel and the sponge- immobilize proteins [13]. Common sponges vary in length
gourd, which has a multidirectional array of fibers compris- from around 15–25 cm to 1.20–1.50 m [12,14].
ing a natural mat, presents an inner fiber core (Fig. 1(c)) and When searching for new applications for a particular
an outer mat core (Fig. 1(d)). Fig. 2 shows many varieties of material, its thorough characterization is very useful. In
Brazilian sponge-gourds, whereas most of them are used as polymer composites, the surface composition of its
constituents is responsible for many interfacial phenomena
such as adsorption, wetting and adhesion and therefore it is
important to characterize fibers before and after their
chemical treatment to evaluate the use of L. cylindrica in
biocomposites.
In this work, sponge-gourds were comprehensively
characterized by various analytic techniques. The effect of
different chemical treatments on the fibers was also
investigated. This study attempts therefore to address
important characteristics of the fibers in order to aid their
increasing utilization in present and future applications such
as polymeric biocomposites.

2. Experimental methods

Sponge-gourds from L. cylindrica, or simply luffa, from

the Southeast region of Brazil were used in this work.
Holocellulose, a-cellulose and hemicellulose (TAPPI T257
om-85), lignin (TAPPI T222 om-88), extractives (TAPPI
T264 om-88), moisture (ABCP M1) and ash content (TAPPI
T211 om-93) of luffa were determined by commonly used
standards. The samples were prepared prior to these
determinations according to TAPPI T262 om-88.
Solubility in hot and cold water and in NaOH 1% at
100 8C were determined by TAPPI T 207 om-88 and TAPPI
T 212 om-88 standards, respectively. Fiber apparent density
and diameter, for the different fiber regions, were evaluated
with a pycnometer and an OLYMPUS BX-60 optical
microscope, respectively.
Fig. 1. The L. cylindrica plant (a) and fruit (b), the inner fiber core XPS/ESCA of the surface of the fibers was carried out
(c) and the outer core open as a mat (d). with a Multilab ESCA 3000 VG Microtech (Mg Ka).
476 V.O.A. Tanobe et al. / Polymer Testing 24 (2005) 474–482

to 560 8C) in a N2 atmosphere. Treated fibers were also

analyzed with a BOMEM Hartmann MBSeries Infrared
spectroscopy equipment in order to identify possible fiber
chemical alterations.
The degree of crystallinity of the fibers was calculated
from X-ray diffractograms recorded on a Rigaku/Philips
X-ray diffractometer with Ni-filtered Co Ka radiation at
40 kV and 20 mA. Computer software was used for the
deconvolution of the spectra to evaluate the percent
crystallinity (IC) of the samples by an area method [15]:
ACrystalline
ICð%Þ Z !100 (1)
ATotal
Fig. 3. Optical microscope photo (40!) of a single untreated
L. cylindrica fiber. The crystalline region of the ligno-cellulosic material is
associated with peaks at 2qZ22 and 238 and 2qZ18 and 228
A Phillips scanning electron microscope, model XL-30, (for celluloses I and II, respectively). The amorphous region
was used to study fiber surface topography. Before is associated with peaks at 2qZ18 and 198, and cellulose I
examination, the fiber samples were sputter-coated with and II are associated with 2qZ13 and 158, respectively.
a thin layer of gold in a vacuum chamber. Thermogravi- For the chemical treatment, the ground fibers were
metric analysis (TGA) was carried out in a Netzsch DSC thoroughly washed in distilled water and dried in air at room
209 at a heating rate of 20 8C/min (room temperature temperature (24 h). Treatment was carried out by steeping

Fig. 4. SEM micrographs (!400) of (a) untreated L. cylindrica fibers, and NaOH treated fibers for (b) 10 min, (c) 60 min, and (d) 90 min.
 V.O.A. Tanobe et al. / Polymer Testing 24 (2005) 474–482 477

Fig. 5. SEM micrographs (!400) of methacrylamide treated L. cylindrica fibers for (a) 1% 120 min, (a) 1% 180 min, (c) 3% 120 min, and (d)
3% 180 min.

the fibers in 2% (w/w) NaOH (10, 60 or 90 min) or

Table 1
methacrylamide aqueous solutions, at different concen-
Fiber weight reduction for different treatment conditions (room
trations 1, 2 or 3% (60, 120 or 180 min). Treated luffa fibers
temperature)
were then washed with water until a neutral pH was reached
and finally dried at 60 8C for 24 h. Methacrylamide Time (min) Weight reduction
(%) (%)
1 60 1.1
120 5.1
3. Results 180 4.7
2 60 1.6
Fig. 3 shows an optical microscope photo of a single 120 5.0
180 4.9
luffa fiber where the large variation of fiber diameter that can
3 60 6.4
occur in a single fiber can be observed. Analysis of diameter
120 6.2
variation showed a mean value of 0.631G0.217 mm 180 6.1
(maximum 1.000 mm and minimum 0.200 mm) and, as
478 V.O.A. Tanobe et al. / Polymer Testing 24 (2005) 474–482

Fig. 6. Thermogravimetric analyses of untreated and treated L. cylindrica fibers.

expected, natural fibers present a wide range of diameters, aspect also showed a different shade of beige. The
which contributes to their property variations. methacrylamide treatment resulted in very silky and nearly
The apparent density of luffa was determined as 0.92 white-colored fibers for all concentrations.
(G0.05) g/cm3, although the density of vegetable fibers Chemical treatment was responsible for a weight
[16] are usually higher than 1 g/cm3. These data may be reduction of approximately 6% for all treatments with
particularly useful when using these fibers in applications NaOH. Methacrylamide (Table 1), on the other hand, only
such as composite materials. Density of treated fibers showed this kind of reduction for the most severe
could not be evaluated with the described methodology treatments. It is interesting to notice that the 3% treatment
because when in contact with the fluids used (water or reached 6% reduction for all treatment times, whereas the 1
ethanol) the fibers produced bubbles which invalidated and 2% treatments for 60 min did not significantly affect the
the measurements. original weight.
Fig. 4 presents SEM micrographs of the surface TGA of a luffa sample is shown in Fig. 6. The fiber mass
morphology of luffa. It can be seen that the fibers show a decreased from about 93 (at 100 8C) to 89 (at 250 8C) and to
homogeneous aspect, with a rough surface and an outer 32% (at 350 8C). Different regions can be associated with
lignin rich layer around the fibers [14].
NaOH treated fibers show an irregular surface, which is
more accentuated for the harsher treatments due to greater
levels of surface material being removed. Methacrylamide
results in a more severe treatment of the fiber with
permanent damage to fiber integrity, as can be seen in
Fig. 5. The exposing of the fiber inner layers is more evident
as the treatment conditions become more severe.
Handling of untreated fibers revealed a rougher aspect
compared to the smooth NaOH treated fibers. The visual

Table 2
Chemical composition of L. cylindrica

Component Content (%)

Holocellulose 82.4
a-Cellulose 63.0
Hemicellulose 19.4
Lignin 11.2
Extractives 3.2 Fig. 7. Fourier transform infrared spectra corresponding to: (a)
Ashes 0.4 untreated L. cylindrica fibers, (b) 2% NaOH treated fibers for
90 min, and (c) 3% methacrylamide treated fibers for 180 min.
 V.O.A. Tanobe et al. / Polymer Testing 24 (2005) 474–482 479

Table 3 the loss of retained water at 100 8C, hemicellulose

Peak positions of untreated L. cylindrica degradation in the 200–260 8C region, cellulose degradation
Wave number (cmK1) Assignment at 240–350 8C and lignin degradation at 280–500 8C [17,
3370 OH stretching
18]. Between 100 and 250 8C, degradation turns the ligno-
2870 Saturated C–H stretching cellulosic fiber into a brownish color material, losing its
1730 CaO stretching of acetyl or strength, although this was not quantified. At higher
carboxylic acid temperatures, up to 500 8C, carbonization occurs with
1636 Absorbed H2O accentuated loss of material.
1505 Aromatic bending C–H (ring) The degradation reactions of lignin and cellulose become
1470 Lignin and CH2 sym. Bending exothermic at about 270 and 300 8C, respectively. Pyrolysis
pyran ring
of a-cellulose occurs at about 300 8C and of lignin at about
1417 CH2 bending (cellulose)
1355 O–H in plane bending (cellulose) 400 8C, while hemicellulose decomposes at a considerably
1162 Antisym. bridge C–OR–C lower temperature [17]. The TGA curve profile for the
stretching (cellulose) untreated fibers was similar to referenced work [14].
1110 Anhydroglucose ring Treated fibers showed a slight increase in thermal
1055 C–OR stretching (cellulose) resistance. Temperatures higher than 250 8C showed the
884 Antisym., out of phase ring largest differences, although the fiber at this point has
stretching already undergone severe thermal degradation. It has not
been possible to detect significant variations between
treatments via this technique.
Although some work has already been reported regard-
ing luffa chemical characterization [3], a complete chemical
analysis has not been cited. Table 2 shows the chemical
analysis of luffa. The cellulose content was similar to that
reported for sisal, jute, hemp and abaca (Manila), lignin
content was similar to hemp, banana and abaca (Manila),
whereas ash content was similar to agave, bagasse and abaca
(Manila) [19].
Certainly, the luffa composition will be very much
dependent on various factors, such as species, variety, soil
type, weather conditions, plant age, etc. and therefore the
data here has been included as a basis of comparison for
future authors.
Fig. 7 shows FTIR spectra of luffa and Table 3 specifies
Fig. 8. X-ray diffraction pattern of untreated L. cylindrica fibers. observed absorptions. The untreated fibers show intense,
characteristic peaks at about 1595 cmK1 (free hydroxyl

Fig. 9. X-Ray crystallinity index for L. cylindrica fibers treated under different conditions.
480 V.O.A. Tanobe et al. / Polymer Testing 24 (2005) 474–482

band), 1740 cmK1 (acid carbonyl absorption), 2750–

2800 cmK1 (typical CH2 and CH), 3200–3300 cmK1 (the
O–H stretching band), 1100 cmK1 (C–O–C absorption), and
at 1000–1500 cmK1 (the aromatic region related to the
lignin) [20,21].
NaOH treated fibers do not show the strong absorption at
1735 cmK1 (the carboxyl group: –O–CaO) and there is a
band reduction at 1245 cmK1 (C–H). The former is the most
reported FT-IR alteration due to alkaline treatment [22].
Methacrylamide treated fibers, however, did not evidence
any alteration. The bands could not be clearly identified due
to possible superimposed peaks in the range of 1630–1680
Fig. 10. Photoelectron spectrum shown over a binding energy range and 1550–1640 cmK1 that would be a consequence of the
of 0–1200 eV. (a) Untreated fiber and (b) methacrylamide treated
amide I and amide II groups [23].
(1%, 180 min) fiber.
Fig. 8 shows X-ray diffraction pattern of the fibers and in
Fig. 9 crystallinity indices are compared. Although the fiber
Table 4 crystallinity index (IC) tended to increase after chemical
XPS chemical composition of L. cylindrica samples treatment, from 59.1 to 62.9 (mean value for NaOH) and
Fiber treatment Elements % O/C 62.5% (mean value for methacrylamide), the treatments did
Untreated C 64.0 0.54
not show a homogeneous effect on the fibers, causing scatter
O 34.9 of the results, and therefore this increase may not be
N 1.2 significant. Nevertheless, different chemical treatments of
Methacrylamide C 63.1 0.57 various fibers seem to increase their crystallinity index as it
1% (180 min) O 36.4 has already been reported [22,24].
N 0.5 Fig. 10 shows the XPS spectra of luffa where carbon,
oxygen and nitrogen can be inferred due to proteins and
alkaloids characteristic of vegetable materials.

Fig. 11. Deconvolution of a few peaks found in Fig. 10 related to the C-1s (a) untreated fiber and (b) methacrylamide treated (1%, 180 min)
fiber.
 V.O.A. Tanobe et al. / Polymer Testing 24 (2005) 474–482 481

Table 5
Mean values for different fiber evaluations

Untrea- NaOH 2% Methacryla-

ted (90 min) mide 1%
(180 min)
Lignin 11.2 10.9 10.4
Extractives 3.2 1.6 1.7
Ashes 0.4 0.9 0.4
Solubility— 1.6 0.1 0.3
cold water
Solubility— 1.7 1.0 1.0
hot water
Solubility— 12.5 5.5 9.6
NaOH 1%
Fig. 12. ESCA spectra in the range of 22–34 eV, related to the O-2 s. (100 8C)
The identified characteristic binding energy regions for
lignocellulosic materials were: 285 eV (C–H), 286.6 (C–O– solubility due to the extraction of lignin, hemicelulose and
H and C–O–C) and 282.2 (CaO and O–C–O) [25]. From traces of other compounds at high temperature. Regarding
this figure, the values for the concentration of the fiber the NaOH (2%) treated fibers, a smaller solubility than that
chemical surface elements can be estimated (Table 4). The for the untreated fiber was expected. Besides although the
ratio O/C increases with the treatment basically due to methacrylamide treatment removes material from the fiber,
removal of hemicellulose, lignin and extractives. Never- it was ineffective to extract compounds that are soluble in
theless, the O/C ratio (0.57) is an indication that there still is NaOH at 100 8C.
lignin on the surface, when this ratio reaches 0.83 the
sample is said to be pure cellulose, whereas when it is in the
range 0.31–0.40, it is said to be pure lignin [25].
Fig. 11 shows the deconvolution of some peaks found in 4. Conclusions
Fig. 10 related to the C-1s [26], where one can see that the
contribution of the different chemical bonds is altered by Extensive analytical effort to characterize L. cylindrica
chemical treatment. has been made in order to supply data for segments of
In Table 4 it can be noted that the nitrogen content on the industry which already use or may use in the future this
surface decreases with treatment which is not expected promising material.
when a methacrylamide chemical agent is used. This may Different chemical treatments were effective to modify
have happened since the treatment itself removes fiber L. cylindrica fibers. The extent of their impact on the fiber
surface material (Table 1), which has nitrogen in its was found to be dependent on the chemical agent, its
composition. concentration and treatment time. Treatment with NaOH
Fig. 12 presents the XPS spectra of electrons from the O- was found to adequately modify the fiber surface in
2s level where the inclusion of nitrogen on the surface preparation for its use as reinforcement of composite
can be ratified. The alteration of the spectra in the region of materials, whilst not causing such severe damage to the
25–30 eV, which is related to the chemical neighborhood of fiber as the methacrylamide treatment.
the CaO group, suggests that inclusion of N–CaO groups
may be occurring on the surface [27]. The harsher
treatments showed similar results. Acknowledgements
Table 5 shows mean values for different tests regarding
the solubility of the fibers. Fiber solubility in cold water The authors would like to thank DRIANA Buchas,
severally decreased from the untreated value because the LACTEC, Wood and Pulp Laboratory/UFPR, LORXI
chemical treatment is carried out in water, which on its own Laboratory/UFPR, LSI/UFPR and CEPESQ/UFPR.
removes material from the fiber surface, and therefore, when
the solubility measurement is made, little is left to be
removed from the fiber. The solubility in hot water,
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 Update
Polymer Testing
Volume 29, Issue 2, April 2010, Page 288–289

DOI: https://doi.org/10.1016/j.polymertesting.2009.12.009
 Polymer Testing 29 (2010) 288–289

Contents lists available at ScienceDirect

Polymer Testing
journal homepage: www.elsevier.com/locate/polytest

Corrigendum

Corrigendum to ‘‘A comprehensive characterization of chemically treated

Brazilian sponge-gourds (Luffa cylindrica)’’ [Polymer Testing. Volume 24
(2005) p. 474–482]
Valcineide O.A. Tanobe a, Thais H.D. Sydenstricker a,1, Marilda Munaro b, Sandro C. Amico a, *
a
Mechanical Engineering Department, Federal University of Parana, P.O. Box 19011, 81531 990, Curitiba, PR, Brazil
b
Institute for the Development of Technology, LACTEC, Curitiba, PR, Brazil

The authors regret the errors in the above paper.

1) The figure below should replace Fig. 11 of the referred paper.

Fig. 11. Deconvolution of a few peaks found in Fig. 10 related to the C-1s: (a) untreated fiber and (b) methacrylamide treated (1%, 180 min) fiber.

DOI of original article: 10.1016/j.polymertesting.2004.12.004.

* Corresponding author.
E-mail addresses: valcitanobe@yahoo.com.br (V.O.A. Tanobe), tsydenstricker@gmail.com (T.H.D. Sydenstricker), marilda@lactec.org.br (M. Munaro),
amico@ufpr.br (S.C. Amico).

1
Tel.: þ55 41 3361 3430; fax: þ55 41 3361 3129.

0142-9418/$ – see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.polymertesting.2009.12.009
 V.O.A. Tanobe et al. / Polymer Testing 29 (2010) 288–289 289

2) Page 481: The first sentence should read:

The identified characteristic binding energy peaks for these lignocellulosic materials were: 285 eV (C–H), 286.5 (C–O–H
and C–O–C), 287.6 (C]O and O–C–O) and 288.9 (O]C–O), somewhat similar to Tserki et al. (2005) and Gaiolas et al.
(2009).

References added:
C. Gaiolas, M.N. Belgacem, L. Silva, W. Thielemans, A.P. Costa, M. Nunes, M.J.S. Silva. Green chemicals and process to graft
cellulose fibers. Journal of Colloid and Interface Science 2009;330(2):298-302.
V. Tserki, N.E. Zafeiropoulos, F. Simon, C. Panayiotou. A study of the effect of acetylation and propionylation surface
treatments on natural fibres. Composites Part A-Applied Science and Manufacturing 2005;36(8):1110-1118.

The authors would like to apologise for any inconvenience this may have caused to the readers of the journal.