Natural Resources, 2011, 2, 98-101
doi:10.4236/nr.2011.22013 Published Online June 2011 (
Copyright © 2011 SciRes. NR
Tannin-phenol Formaldehyde Resins as Binders
for Cellulosic Fibers: Mechanical Properties
A. S. Hussein1*, K. I. Ibrahim1, K. M. Abdulla2
Polymer Research Center, University of Basrah; State Company for Petrochemical Industries, Basrah , Iraq.
Received December 21st, 2010; revised May 11th, 2011; accepted May 20th, 2011.
In this study Eucalyptus tannin (T) was isolated from outer bark of Eucalyptus trees; as sodium phenoxide salt and used
as extender or copolymer into phenol formaldehyde (PF) resin at five percent (10, 20, 30, 40 and 50)% W/W. Tan-
nin-phenol formaldehyde (TPF) and tannin formaldehyde-phenol formaldehyde (TFPF) resins that synthesized in this
study were evaluated as adhesive material for cellulosic fibers by study the mechanical properties of the composite
sheets. The results show that the substitu ting of (PF) with tannin at (10-50)% W/W give resins with mechanical proper-
ties comparable or near to those of pure (PF), where the tensile strength at break (Tb) ranging from 15.15 Mpa to 22.27
Mpa as compared with 17.6 Mpa for pure (PF); while the impact strength properties (Im) of composites sheets in-
creased with increased the (T) percents which were about 5.16 KJ/m2 for (TPF-10%) and 7.21 KJ/m2 for
(TPF-50%) .On the other hand modification of (T) to tannin formaldehyde resin (TF) appear less performance at the
results of this study, this effect probably to low p enetration of (TFPF) resins between the small vo ids of cellulose fibers
when soaked it in resin solutions. In gene ral the results of this study ind icate that th e Eucalyptus tann in can be used for
partial sub stitution of (PF) to produce resins with feas ible mechanical properties and can be used in so me applications
of (PF) resins.
Keywords: Tannin, Tannin-formaldehyde Resins, Phenol- formaldehyde Resins, Mechanical Properties
1. Introduction
Tannins are one of the natural products which are widely
distributed in plant kingdom, they are composed of dif-
ferent phenolic compounds [1,2]. Tannins are generally
classified into two major types: hydrolysable tannin s and
condensed tannins, the hydrolysable tannins are mixture
of simple phenols and it has had medicinal and cottage
applications. Condensed tannins are polymeric phenolic
compounds comprising from flavon-3-ol repeating units;
Condensed tannins are known for their wide distribution
in various softwood and hardwood, and it constitute
about 90% of the total world production of commercial
tannins [3].
Many studies show that the phenolic natural of tannin
make it suitable for synthesis polymeric resins and adhe-
sives; Hergert [4] stated that (30-50)% W/W tannin re-
placement of the amino and phenolic resins have been
formulated into wood adhesives. Saayman [5] reported
tannin (Wattle tann in) utility i n PF resins fo r wood adh e-
sives requiring up to 30% of PF fortification to obtain a
fully water–resistant bond. Other studies deal with reac-
tion of tannin (Wattle tannin) with formaldehyde to syn-
thesis polymeric resins [6, 7].
The purpose of this study was to evaluate the per-
formance of Eucalyptus tannin as tannin sodium salt (T)
or as tannin-formaldehyde resin (TF) into PF as binders
for cellulosic fibers to produce composites sheets by
study their mechanical properties.
2. Experimental
2.1. Materials:
Tannin was isolated from the outer bark of Eucalyptus
tree, and used as crude without farther purification. Cel-
lulose fibers (pulp) were used as sheets from National
Company of Papers Industries, other chemicals used in
this study were:
Sodium hydroxide and phosphoric acid from Fluka
Chemical Company Inc.; phenol, ethanol and formalin
solution (37-41)% W/V from (H&W).
2. 2. Instruments:
The tensile properties were measured by using tensile
Tannin–phenol Formaldehyde Resins As Binders for Cellulosic Fibers: Mechanical Properties
strength instrument (I nstron model 1193), an d the impact
strength was measured by impact testing instrument
(Universal Pendulums model 6546/000), with 2J pendu-
lum energy.
The composite sheets that prepared from these resins
that synthesized in this study with cellulose fibers were
cut into tensile test sp ecimens (Dumbbell shape) and in to
impact test specimens by dumbbell cutter (Automatic
Hollow Dipunch, made by Ceast Company). The sam-
ples sheets were compression–molded using hydrolic
press (F. & R. AL-Haddad Co.).
Dimensions of the samples were measured by mi-
crometer (Brown & Shape micrometer); (TMT Notch
cutter model 43-15-1) was used for notching the impact
test specimens.
2.3. Isolation of Tannin:
The powder of Eucalyptus outer bark was refluxed with
sodium hydroxide solution 2% for 24 hr., and then the
miture allowed to cool and filtrated. Sodium tannin
phenoxide was used as tannin without naturalized or far-
ther purification, the yield of it is about (48 – 50)% per
total solids used (ba rk and so di um hydroxid e).
2.4. Resins Synthesis:
TF resin was synthesized adopting the following proce-
dure: 10 g tannin was dissolved in 50 ml water, the PH of
solution was adjusted to (10-11) by added some drops
from 10% NaOH solution, the temperature o f the soltion
raised to 80˚C with stirring for 75 min. Afterwards the
solution was allowed to cool to 60˚C, then 40 ml from
formalin solution was added, the temperature of the
mixture was kept at 60˚C; the reaction time was about 3
Tannin resins that synthesized consist of tannin-phenol
formaldehyde (TPF), and tannin formaldehyde–phenol
formaldehyde (TFPF); at five percent from tannin in the
final resin (10, 20 , 30 , 40 and 50 )% W/W.
PF resin was synthesized according to the procedure
described in references 8 and 9; TPF resins were synth-
sized by mixing the solution of predetermined weight of
tannin with the mount of PF that give required propor-
TFPF resins at (10, 20, 30, 40 and 50)% from tannin
were prepared by allowed the some method of TPF syn-
2.5. Production of Composite Boards:
The composite boards were prepared by soaking the cel-
lulose fibers in 20% W/V of resin solutions for 24 hr.,
then dried at room temperature and cut into test speci-
mens. Test samples compressed under 150 psi pressure,
at (160-170)˚C for 10 min. The impact test samples had
dimensions of (1 cm width, 0.2-0.17 cm thickness and 5
cm length). While the tensile test samples had 11.5 cm
length, (0.2-0.17) cm thickness and 0.6 cm width.
3. Measurements:
The tensile properties were measured at across head
speed 50 mm/min. and recorder speed 10 mm/min.; five
samples were made for each test, the tensile strength
tests carried out at 25˚C and according to the ASTM–
D638-72(1986)[10a]. While the impact resistance acord-
ing to ASTM D256-56(1986)[10b].
4. Results and Discussion
Many study focused to reduced the cost of phenolic res-
ins and to reduced their toxicity on humans and on the
environment; some of this are used lignin and it's deriva-
tives [12-14], another tries about using of tannins or
other natural products [15,16].
In this study the effects of Eucalpytus tannin and it’s
methylol derivative on the adhesion properties of PF for
cellulose fibers was examined and evaluate the perform-
ance of these resins which contain tannin (T) or tannin
formaldehyde (TF) as binders resins by study the me-
chanical properties of final composites sheets that made
by it after thermal curing under press. The ten sile proper-
ties of materials evaluated the rigidity, cross-linking, and
flexibility of it. However the tensile strength of these
composites (resins) showed in Figure 1 and Figure 2; it
indicate that the tensile of the samples made by (10-30)%
tannin or tannin formaldehyde decrease relative to that of
the sample which made by pure PF resin, where the ten-
sile of the resins that contain tannin or tannin formalde-
hyde at all percent lower than of the pure PF except the
resins that contain (40-50)% W/W tannin have tensile
values higher than that of PF.
This behavior mean that tannin or tannin formaldhyde
resin decreased the amount of resins that act as binder
because tannin not contain reactive functional groups can
bonded in the network of resin matrix, on the other hand
Figure 1. Tensile strength of TPF resins-cellulose fibers
composite at different percent of tannin.
Copyright © 2011 SciRes. NR
100 Tannin–phenol Formaldehyde Resins As Binders for Cellulosic Fibers: Mechanical Properties
Figure 2. Tensile strength of TFPF resins-cellulose fibers
composite at different percent tannin formaldehyde.
no significant effect to methylol groups of TF; Figure 2.
this may be result to some factors of TFPF resin solu-
tions or to method of cellulose fibers-resins samples
preparation. The results showed in Figure 1 and 2 indi-
cate that the tensile strength of the samples not continue
in decreasing at percent of 10%, 20% and 30% from T or
TF which about (15.15-15 .01) Mpa and (13.6-13.1) Mpa
respectively; in spite of reduce the amount of PF portion;
there are some effects for T or TF in the final properties
of the composites these effects may come from action of
tannin as fillers which generally increase the rigidity of
the samples or by act as extender with limit activity for
tannin ability to form methylol groups when react with
formaldehyde during hot press then can participate with
PF in the formation of network resins but at little func-
tional groups [17]; and the high density of polar func-
tional groups in tannin lead to th is behavior.
On the other hand, the impact strength of TPF resins
treated cellulose fibers (Figure 4 and 5) at T percent
10% and 20% were lower than that of pure PF.
While the resins of 30%, 40% and 50% TPF gave an
impact strength equal to that of pure PF about 7.2 KJ/m2,
this brittleness appears to be the result to the action of
tannin as fillers and also for behave of it as across-link-
ing agent for substituted the lower levels of PF that
needed to obtained similar mechanical properties. As can
see the modification of T to TF did not improved the
Figure 4. Impact strength of TPF resins–cellulose fibers
Figure 5. Impact strength of TFPF resins–cellulose fibers
adhesion properties of these resins (Figure 5); the ob-
served impact strength values of most composites that
contain TF were generally higher than this contain 100%
PF, only one resin (TFPF-10%) have impact value less
than others; this flexibility appear to be the result to low
diffusion of resins between the fibers. Therefore replace
the soaking method by mixing the resins with fibers me-
chanically is expected to give samples with better me-
chanical and adhesion properties due to facilitate the
diffusion and p enet rat i o n of re sins.
5. Conclusions
Used Eucalyptus tannin as tannin sodium salt into PF
resin at (10, 20, 30, 40 and 50)% W/W can produce cel-
lulose fibers-TPF composite sheets with mechanical
properties comparable to that made with pure PF. The
composed sheets produced by used tannin-formaldehyde
resin into PF resin show lower satisfactory results. At the
limited mechanical properties of this study; the used of
Eucalyptus tannin as TPF or TFPF resins appear to be
practically to reduced the ratio of PF in some of it's ap-
plications, Tannin act as filler or extender to participate
in the formation adhesive bonds but at lower level and
[1] M. Belgacem and A. Gandini, “Monomers, Polymers and
Composites from Renewable Resources,” Elsevier Ltd.
Cambridge, 2008, PP. 179-200.
[2] J. M. Chesworth, T. Stuchbury and J. R. Scaif, “An In-
troduction to Agricultural Biochemistry,” Chapman and
Hall, London, 1998, pp. 55-58.
[3] J. M. Garro Galvez, B. Riedl and A. H. Conner, “Ana-
lytical Studies on Tara Tannins,” Holzforschung, Vol. 51,
No. 3, 1997, pp. 235-243.doi:10.1515/hfsg.1997.51.3.235
[4] R. W. Hemingway and A. H. Conner (eds), “Adhesives
from Renewable Resource,” ACS symposium series 285,
Am. Chem. Soc., Washington, 1989, pp. 155-171.
[5] H. M. Saayman and J. A. Qatly, “Wood Adhesives from
Wattle Bark Extract,” Proceeding of the conference on
wood gluing. International Union of Forestry Research
opyright © 2011 SciRes. NR
Tannin–phenol Formaldehyde Resins As Binders for Cellulosic Fibers: Mechanical Properties
Copyright © 2011 SciRes. NR
Organization, Madison, 22-23 September 1975, pp.
[6] S. Kim and H. -J. Kim, “Evaluation of Formaldehyde
Emission of Pine and Wattle Tannin-Based Adhesives by
Gas Chromatography,” Holz Roh Werkst, Vol. 62, No. 2,
2004, pp. 101-106. doi:10.1515/hfsg.1997.51.3.235
[7] M. T. Paridah and O. C. Musgrave, “Alkline Treatment
of Sulfited Tannin-Based Adhesive from Mangrove to
Increase Bond Integrity of Beech Slips,” Journal of
Tropical Forest Science, Vol. 18, 2006, pp. 137-143.
[8] G. A. Adam, “Chemistry and Technology of Methylolic
Resins: Their Derivatives and IPNs,” National journal of
Chemistry, Vol. 1, 2001, pp. 131-157.
[9] A. K. Raheem, “Synthesis, Characterization and Study of
Some New Epoxy Resins and Resinous Amines as Hard-
ners,” Ph.D. Thesis, University of Basrah, Basrah, 1992.
[10] A-Annual book of ASTM Standard, “Tensile Properties
of Plastics,” Vol. 8.1, 1986, D638-84. B-Annual book of
ASTM Standard, “Standard Test Methods for Impact Re-
sistance of Plastics and Electrical Insulating Materials,”
Vol. 8.1, 1986, D256-84.
[11] M. Olivares, H. Aceituno, G. Neiman, E. Rivera and T.
Sellers, “Ligin-Modified Phenolic Adhesives for Bonding
Radiata Pine Plywood,” Forest product Journal, vol. 45,
No. 1, 1995, pp. 63-67.
[12] T. Sellers, “Survey Reveals Use of Lignin as Partial Sub-
stitute for Phenol,” Panel World, Vol. 31, 1990, pp.
[13] R. W. Hemingway, A. H. Conner and S. J. Branham,
“Adhesives from Renewable Resources,” ACS Sympo-
sium, Washington, 1989, pp. 13-42.
[14] A. Pizzi, “Advanceed Wood Adhesives Technology,”
Marcel Dekker, New York, 1994, pp. 149-217.
[15] M. D. Fabricio and A. R. L. Francisco, “Alternative Cas-
tor Oil-Based Polyurthane Adhesives Used in Production
of Plywood,” Materials Research, Vol. 7, No. 3, 2004, p.
413. doi:10.1590/S1516-14392004000300007
[16] D. J. Gardner, S. K. Waage and T. J. Elder, “Bonding
Flakeboard with Filled and Extended Phe-
nol-Formaldehyde Resin,” Forest Products Journal, Vol.
40, 1990, pp. 31-36.