A preliminary assay of the potential of soy protein isolate and its hydrolysates to provide interfiber bonding enhancements in lignocellulosic furnishes

Article abstract of DOI:10.1016/j.reactfunctpolym.2014.09.021

Soy protein isolate (SPI) was extracted from soy flour and hydrolyzed with hydrochloric acid, sodium hydroxide, and enzyme, separately, to provide a series of hydrolysates. The SPI and its hydrolysis products were later cross-linked with ethylendiaminetetraacetic acid (EDTA) in the presence of sodium hypophosphite (SPH) after which they were complexed to chitosan as part of an on-going general chemical strategy in our laboratories to improve their incorporation into old corrugated container (OCC) matrix and thus increase inter-fiber bonding. Approximately 2% SPI-EDTA-chitosan and hydrolyzed SPI-EDTA-chitosan additives by mass (OCC-based slurry) were thoroughly mixed before generating a sheet for physical testing. The tensile and burst indices of the SPI-EDTA-chitosan additive-treated OCC pulp sheet increased 46.3% and 61.85%, respectively, while the inter fiber bonding of SPI-EDTA-chitosan additive-treated OCC pulp sheet increased 74.86% compared to the control, albeit having a decreased tear strength and roughness, with significantly increased gloss. The additive-treated pulp sheet was characterized by thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and ATR to provide evidence for product synthesis.

Full text of DOI:10.1016/j.reactfunctpolym.2014.09.021

Reactive & Functional Polymers 85 (2014) 228–234
Contents lists available at ScienceDirect
Reactive & Functional Polymers
journal homepage: www.elsevier.com/locate/react
A preliminary assay of the potential of soy protein isolate
and its hydrolysates to provide interfiber bonding enhancements
in lignocellulosic furnishes
b
Abdus Salam a,b,c, Lucian A. Lucia a,b,c, , Hasan Jameel
⇑
a Qilu University of Technology, Key Laboratory of Pulp & Paper Science and Technology, Jinan 250353, PR China
b Laboratory of Soft Materials & Green Chemistry, North Carolina State University, Department of Forest Biomaterials, Raleigh, NC 27695-8005, United States
c Laboratory of Soft Materials & Green Chemistry, North Carolina State University, Department of Chemistry, Raleigh, NC 27695-8204, United States
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 13 June 2014
Received in revised form 4 September 2014
Accepted 23 September 2014
Available online 2 October 2014
Soy protein isolate (SPI) was extracted from soy flour and hydrolyzed with hydrochloric acid, sodium
hydroxide, and enzyme, separately, to provide a series of hydrolysates. The SPI and its hydrolysis
products were later cross-linked with ethylendiaminetetraacetic acid (EDTA) in the presence of sodium
hypophosphite (SPH) after which they were complexed to chitosan as part of an on-going general
chemical strategy in our laboratories to improve their incorporation into old corrugated container
(OCC) matrix and thus increase inter-fiber bonding. Approximately 2% SPI-EDTA-chitosan and hydrolyzed
SPI-EDTA-chitosan additives by mass (OCC-based slurry) were thoroughly mixed before generating a
sheet for physical testing. The tensile and burst indices of the SPI-EDTA-chitosan additive-treated OCC
pulp sheet increased 46.3% and 61.85%, respectively, while the inter fiber bonding of SPI-EDTA-chitosan
additive-treated OCC pulp sheet increased 74.86% compared to the control, albeit having a decreased
tear strength and roughness, with significantly increased gloss. The additive-treated pulp sheet was
characterized by thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and ATR to
provide evidence for product synthesis.
Keywords:
Soy protein isolate
Hydrolysates
Chitosan
Complexation
OCC pulp
Physical properties
Ó 2014 Elsevier B.V. All rights reserved.
1. Introduction
relatively costly chemical additives such as cationic starch or poly-
acrylamides. The low cost, commercial availability, and chemical
Soy protein isolate is a long chain biopolymer consisting of 18
different polar and nonpolar amino acids. Polar amino acids such
as cysteine, arginine, lysine, histidine and others can act as effec-
tive chemical pivots to crosslink the protein and improve the
mechanical, thermal, and physical properties, while reducing
water sensitivity and hydrophilicity [1]. Earlier research reported
that isolated soy proteins may be cross linked with aldehydes such
as formaldehyde, glutaraldehyde (GA), glyoxal, and glyceraldehyde
through Maillard reactions [2]. Isolated soy proteins cross linked
with GA yield biopolymers with enhanced mechanical properties
[3]. Chemical modification of pulp fibers within the pulp & paper
market is currently a common practice for improving printing
quality, surface gloss, surface sizing, and calendaring. In addition,
mechanical property improvements tend to be regulated by
derivatization power of soy protein flour (>50% protein), not sur-
prisingly, is extremely attractive for the development of novel
functional soy protein derivatives for paper strength improve-
ments. Typically, starch is used for printing and writing grade
papers for surface sizing, i.e., for improving paper surface resis-
tance to uneven penetration and flow of inks/liquid media and
acceptable printability [4]. The reclaimed paper market has been
mostly focused on attaining improved mechanical strength
properties.
Within the reclaimed paper market, the utilization rate of waste
old corrugated containers (OCC) (recycled containerboards) in
1963 was 21.1% in the US, while in 2001 it increased to 67% with
a recovery rate of nearly 70% [5]. Recently, the American Forest &
Paper Association (AF&PA) released a 2011 recovery rate for OCC
with a new high of 91.2 percent. Therefore, research in this area
is necessary to improve the strength of OCC because waste fibers
are typically mechanically inferior to their virgin equivalents. Early
work identified several chemical treatments that yielded improve-
ments in the bonding strength of recycled sheets [6,7]. Further
innovative studies have shown that fiber surface chemical
⇑
Corresponding author. Address: Qilu University of Technology, School of
Papermaking and Plant Resources Engineering, Key Laboratory of Pulp & Paper
Science and Technology, No. 3501 Daxue Road, Changqing District, Jinan City,
Shandong Province 250353, PR China.
E-mail address: lalucia@ncsu.edu (L.A. Lucia).
http://dx.doi.org/10.1016/j.reactfunctpolym.2014.09.021
1381-5148/Ó 2014 Elsevier B.V. All rights reserved.

A. Salam et al. / Reactive & Functional Polymers 85 (2014) 228–234
229
derivatization can prevent strength losses [8,9]. The paper industry
is currently using commercial dry strength agents such as cationic
starch, polyacrylamide, and glyoxylate polyacrylamide to improve
the strength of OCC, but the improvement is still very low relative
to virgin pulp [10,11]. In addition, a number of these studies
have been conducted with nonrenewable inorganic fillers and
petroleum-based matrices for applications that include packaging,
a high value sector of the pulp market. Increasing environmental
concerns have led to new flexible barrier bio-based packaging
materials and the potential uses of renewable resources to offset
the use of the inorganic fillers and petroleum-based materials [12].
The present study focuses on the application of an isolated soy
protein derivative for improving the mechanical properties of OCC.
It will focus on the characterization of the soy protein derivatives
and explore their applicability to OCC.
2.3. Chemical modifications of soy protein isolate (SPI) and hydrolyzed
soy protein isolate
Into 15 mL of 1 N sodium hydroxide solution in a 50 ml Petri
Dish, 5 g of EDTA and 1 g of SHP were dissolved. Soy protein isolate
or hydrolyzed soy protein isolate (5 g) was added to the solution
and manually mixed with a glass rod. The mixture was placed in
an oven at 130 °C for 3 h. Reaction products were washed with
water and filtered several times to remove unreacted materials.
The product obtained was a modified soy protein isolate that
was air dried at 50 °C in an oven overnight [16]. The proposed
reaction scheme is shown in Fig. 1.
2.4. Polyelectrolyte complexation
Chitosan (Ch, 1 g) was dissolved into 50 ml of 1.5% acetic acid
solution. Modified soy protein isolate (1 g) was dissolved with
50 ml water and added to a 50 ml chitosan solution in a 250 ml
round bottom flask. The reaction mixture was stirred at 70 °C for
90 min [17]. The proposed reaction scheme is shown in Fig. 2.
2. Experimental
2.1. Materials
Soy flour was provided by Archer Daniel Midland (ADM,
Decatur, IL). The OCC pulp was furnished by Azko Nobel Pulp and
Performance Chemicals, Marietta, GA. Commercial dry strength
agents such as Glyoxylate-PAM and cationic starch were supplied
by Azko Nobel Chemicals, Marietta, GA and Cargill Incorporated,
Minneapolis, MN, respectively. Cross linking agents such as
ethylenediaminetetraacetic acid (EDTA) and chitosan (Ch) were
purchased from Sigma–Aldrich and used as received. Chemicals
of reagent grade utilized were sodium hypophosphite, (SHP) CAS
registry number 123333-67-5, sodium hydroxide, CAS registry
number 1310-73-2, Alcalase product No. 126741, and denatured
alcohol and acetic acid from Fisher Scientific, Fair Lawn, NJ.
Deionized water was used for all experiments that required water
as the medium.
2.5. Preparation of OCC pulp sheet
The sheet was prepared according to TAPPI Standard Method T
205 using a 600 ml pulp slurry (1.8 g oven dried OCC pulp) in a
sheet molder machine. The pulp slurry was diluted with 10 L of
DI water in a sheet molder to produce a uniform sheet. The sheet
was conditioned and cured at 105 °C for 1.0 h [17].
3. Testing methods
3.1. Determination of carboxyl content
A known amount of soy protein isolate derivative was dissolved
in 0.1 N NaOH and hydrolyzed for one hour. The excess amount
of NaOH was determined by titration with 0.1 N HCl using
phenolphthalein as an indicator [18] while the carboxyl content
in milliequivalents (meq.) per 100 g was calculated as follows:
2.1. Extraction of the soy protein isolate
Soy flour was carefully added into acidified water so that
solution pH was within the isoelectric range of the soy protein
(pH 4.0–4.8) and that only the soluble fraction of the soy flour
dissolved. The resulting mixture was centrifuged to separate the
protein-rich precipitate from the supernatant to give a high quality
concentrate soy protein [13].
ðV2 ꢀ V1Þ ꢁ N ꢁ 10
Carboxyl Content ðmeqÞ ¼
N = Normality of HCl
ð1Þ
W
V2 = Volume of HCl without sample
V1 = Volume of HCl with sample
W = Weight of Sample.
2.2. Hydrolysis of the soy protein isolate
3.2. Gloss testing
For hydrolysis of soy protein isolate, three different routes were
followed: acid, alkali, and enzymatic treatments. Approximately
1 g of soy protein isolate was added into 50 ml of 1 N HCl or NaOH
solution and heated at 70 °C for 3 h. The suspension was centri-
fuged at 5300 rpm for 15 min. to concentrate the hydrolyzed soy
protein isolate and remove the excess aqueous acid or alkali. The
resultant precipitate was rinsed and re-centrifuged until constant
neutral pH [14]. The enzymatic hydrolysis was carried out with
Alcalase as follows: soy protein isolate was dissolved in water at
50 °C for 10 min. When the protein solution temperature reached
50 °C, the Alcalase (2.4U/g) was added. The soy protein isolate
and enzyme ratio was 1:0.002. pH of solution was maintained at
7 by adding 1 N NaOH during the first 15 min. of reaction,
while at the end of reaction, pH was adjusted to 4.5 using 1 N
HCl. The mixture was cooled, adjusted to pH 7.0, and heated at
95 °C for 15 min. to inactivate the enzyme. The enzymatic
hydrolyzed soy protein isolate was centrifuged, rinsed, and
re-centrifuged until constant neutral pH [15]. The mixture was
freeze-dried and stored.
The gloss of OCC pulp hand sheet was tested with
GLOSSMETER according to TAPPI T 480 test method.
a
3.3. Roughness testing
The roughness of OCC pulp hand sheet was tested with an L & W
roughness tester according to TAPPI T 538 test method.
3.4. Tensile strength
The tensile of OCC pulp hand sheet strength was tested with an
ALWETRON TH1 tester according to TAPPI T 220 test method.
3.5. Burst strength
The burst strength of OCC pulp hand sheet was tested with a
MULLEN tester according to TAPPI T810 test method.

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A. Salam et al. / Reactive & Functional Polymers 85 (2014) 228–234
3.6. Tear strength
4.1.1. ATR analysis
The ATR spectra of the soy protein isolate and soy protein iso-
late-EDTA are shown in Fig. 3. The spectrum of soy protein isolate
shows a prominent peak at 1635 cmꢀ1 which can be ascribed to the
amide linkage of the soy protein isolate, although the carbonyl
region does not clearly show a carbonyl stretch. However, when
the soy protein isolate was reacted with EDTA, a peak appeared
at approximately 1740 cmꢀ1 that is attributable to the carbonyl
group. The appearance of the peak provided compelling evidence
that EDTA is cross linked to the soy protein isolate [18].
The tear strength of OCC pulp hand sheet was tested with an L &
W tester according to ASTM D 689 test method.
3.7. Inter fiber bonding strength
The inter-fiber bonding strength of additive-treated OCC pulp
hand sheets was obtained using
a standard T 569 pm-00
(provisional method-2000@ 2000 TAPPI) testing protocol.
3.8. ATR analyses
4.1.2. Thermal behavior
The thermogravimetric behavior of the soy protein isolate
derivatives was evaluated over a 5 °C/minute heating ramp under
nitrogen and shown in Fig. 4. The weight loss below and near
100 °C was attributed to water evaporation [20]. However, the
weight loss above 100 °C was due to thermal decomposition of
the soy protein isolate derivatives [22]. EDTA had a single sharp
decomposition peak at 228.6 °C, whereas the soy protein isolate
showed a single weight loss peak at 301.15 °C; however, all deriv-
atives of soy protein isolate show a decrease in their respective
maxima for degradation temperature and weight loss, and also sig-
nificantly higher residual mass after heating to 600 °C. This may be
explained by the fact that the soy protein isolate surface-modifying
agents on the surface of the soy protein isolate have a lower
decomposition temperature and are attached via relatively labile
ester bonds that also have a lower temperature of degradation
[18].
IR Spectra of all modified soy flour samples were recorded on a
Perkin Elmer ATR spectrophotometer [19].
3.9. Thermal gravimetric analyses (TGA)
The TGA used in this study was a TGA Q500 (TA Inc., New Castle,
DE) under a nitrogen atmosphere. The temperature range and
heating ramp were 30–600 °C and 5 °C/min, followed by isother-
mal heating at 600 °C [20].
3.10. Measurement of storage modulus
Dynamic mechanical analysis was performed using a DMA
Model 2980 (TA Inc., New Castle, DE) in the film tension mode.
The specimen dimensions were 30 mm in length, 10 mm in width,
and 0.3 mm in thickness. Samples were heated from 30 to 200 °C
using a temperature ramp of 3 °C/min (20 lm amplitude, at
1 Hz) [21].
4.2. Application of soy protein isolate-EDTA-chitosan derivatives for
OCC strength improvement
4. Results and discussion
Mechanical resistance is one of the most important properties
of generic paper substrates. These substrates need to display suffi-
cient resistance in packaging, wrapping, or sealing. In general, such
gross resistance can be attributed at the molecular level to a net-
work of hydrogen bonds. Also, it depends on the quantity and area
of the overall bonding sites. In recycling, fibers are irreversibly
damaged, a fact which affects their final paper resistance proper-
ties. Fig. 5 shows the tensile index of OCC recycled pulp hand sheet
that results after the addition of either virgin (non-recycled) pulp
or dry strength agents.
4.1. Characterization of soy protein isolate derivatives
Soy protein isolate possesses a highly chemically rich surface
covered with amine groups that allow for facile surface decoration
using appropriate reactive species. The reaction pathways that
were chosen for surface functionalization are shown in Figs. 1
and 2. The carboxyl content of the soy protein isolate increased
from 210 meq./100 g in the control to 430 meq./100 g in the test
sample as a result of surface functionalization.
Fig. 1. Esterification reaction of soy protein isolate with EDTA.

A. Salam et al. / Reactive & Functional Polymers 85 (2014) 228–234
231
Fig. 2. Polyelectrolyte complexation of soy protein isolate-EDTA with chitosan.
the adsorption of water, i.e., higher value, less adsorption). Earlier
research reported that the range of tensile index (Nm/g) for OCC
pulp sheet is 20–35 [23]. Defibrillated or non-defibrillated virgin
softwood kraft pulp (revolutions = 5000, CSF = 530) was blended
with OCC recycle pulp (50:50) to increase strength properties. In
addition, 2% SPI derivatives (based on the mass of dried pulp) were
mixed with a separate batch of OCC pulp slurry. The non-defibril-
lated virgin pulp sample demonstrated a decreased tensile index,
but the defibrillated virgin pulp blend sample had a significantly
increased tensile index compared to the control sample (Fig. 5).
This may happen due to a significant decrease in the fiber size
and an increase in the bonded area at the high revolutions (defi-
brillations). The SPI and hydrolyzed SPI did not affect the tensile
index of the OCC pulp hand sheet (Fig. 5).
The tensile indices observed in Fig. 5 from the application of 2%
SPI derivatives-treated OCC pulp are shown as follows where ‘‘(%)’’
is the percentage that the system is superior to the tensile index of
the control (non-treated) sample: SPI-Ch (30.4), SPI-EDTA-Ch
(46.3); acid hydrolyzed: SPI-Ch (29.2), SPI-EDTA-Ch (43.0); alkali
hydrolyzed: SPI-Ch (27.5), SPI-EDTA-Ch (38.4), and enzymatic
hydrolyzed: SPI-Ch (15.9), SPI-EDTA-Ch (27.2). The results were
significantly higher than what has been found for commercial
dry strength additives such as glyoxylate polyacrylamide, cationic
starch, and soy flour. This may be because of the extremely high
level of carboxylic acid and amine groups in soy protein isolate
derivatives that give rise to stronger interactions with OCC pulp
when the sheet is generated with soy protein isolate derivatives
[24,25].
Fig. 3. Shown are ATR spectra of soy protein isolate (A) and soy protein isolate-
EDTA (B). The 1740 cmꢀ1 band can be attributed to the ester carbonyl stretch,
whereas the 1635 cmꢀ1 band is representative of the carbonyl groups in an amide
bond of the soy protein isolate.
In contrast, the tensile indices of 2% SPI-EDTA-Ch, acid hydro-
lyzed SPI-EDTA-Ch and alkali hydrolyzed SPI-EDTA-Ch deriva-
tives-treated OCC pulp samples were also better than defibrillated
virgin pulp blends (Fig. 5). Similarly, the bursting strength %-age
gains of the SPI derivatives-treated OCC pulp sample systems were
‘‘(%)’’ higher than the control: SPI-Ch (44.3), SPI-EDTA-Ch (61.8);
acid hydrolyzed: SPI-Ch (60.7), SPI-EDTA-Ch (64.6); alkali hydro-
lyzed: SPI-Ch (40.8), SPI-EDTA-Ch (57.4), and enzymatic hydro-
lyzed: SPI-Ch (53.9), SPI-EDTA-Ch (65.5), while all the cases
provided better results compared to the commercial dry strength
additive (Fig. 6).
It is also observed from Fig. 7 that the tear strength of all soy
protein isolate and soy protein isolate derivatives-treated OCC pulp
samples were lower than the control sample, but higher than the
glyoxylate polyacrylamide-treated sample.
The t-Test of paired samples (for the mean of the tensile index)
was measured to confirm the significance of the improvements in
tensile index of the additive treated pulp hand sheets. In each of
the cases, an untreated sheet was compared to a sheet formed from
the treated fibers. The t values for the OCC pulp sheet (control) and
SPI-EDTA-Ch, acid hydrolyzed SPI-EDTA-Ch, alkali hydrolyzed SPI-
EDTA-Ch, and enzymatic hydrolyzed SPI-EDTA-Ch-treated OCC
Fig. 4. Thermogravimetric analyses of soy protein isolate (a), soy protein isolate-
EDTA (b), and soy protein isolate-EDTA-chitosan (c).
Virgin pulp has in theory a much higher mechanical resistance
because the fibers have not been reclaimed. The control for these
studies was the base OCC recycled pulp (CSF = 400, a measure of

232
A. Salam et al. / Reactive & Functional Polymers 85 (2014) 228–234
Fig. 5. Tensile strength of soy protein isolate derivative-treated OCC recycle pulp hand sheets.
Fig. 6. Bursting strength of soy protein isolate derivative-treated OCC recycle pulp hand sheets.
pulp sheets were significantly negatively lower than the negative t
table distribution value. The p value of OCC pulp sheet (control)
and SPI-EDTA-Ch, acid hydrolyzed SPI-EDTA-Ch, alkali hydrolyzed
SPI-EDTA-Ch, and enzymatic hydrolyzed SPI-EDTA-Ch-treated
paper making [27]. In addition, the EDTA in soy protein isolate-
EDTA-chitosan derivatives contains a number of free carboxyl
groups (protonated in acidic medium) that can engage in hydrogen
bonds with the fiber surface of pulp and increase the relative
bonded area between fibers. The combined interactive effects
attributable to the carboxylic acid and amine groups for increasing
bonding between fibers during sheet formation also contributed to
an increase in tensile strength [28].
The inter-fiber bonding strength of soy protein isolate-EDTA-
chitosan additive-treated OCC pulp hand sheets increased approx-
imately 74.86% compare to a control OCC pulp hand sheet. It is
likely partially attributable to condensation reactions mediated
by the high temperature (105 °C) that causes two carboxylic acid
groups in EDTA to form an anhydride. Anhydrides can subse-
quently lead to other chemical reactions (e.g., esterification) with
the enriched surface hydroxyl groups of OCC pulp and can
contribute to inter-fiber bonding strength [29]. In addition, a
1.35% higher residual char value was observed in the soy protein
OCC pulp sheets were much lower than the
a value 0.05
(p < 0.05). Therefore, there was significant difference in tensile
indices between the control and soy protein isolate derivatives-
treated pulp sheet samples. In addition, SPI-EDTA-Ch-treated pulp
sheet had significantly increased gloss, but decreased roughness.
This may happen due to increased density of SPI-EDTA-Ch-treated
pulp sheet compared to control sample [26].
4.3. Bond formation with OCC recycle pulp
The basic groups (–NH2) on every ring in soy protein isolate-
EDTA-chitosan derivatives develop positive charges when they
are in a sufficiently acidic medium and can form ionic or covalent
bonds with negatively charged cellulosics in paper fibers during

A. Salam et al. / Reactive & Functional Polymers 85 (2014) 228–234
233
Fig. 7. Tear strength of soy protein isolate derivative-treated OCC recycle pulp hand sheets.
isolate-EDTA-chitosan-treated OCC pulp sheet compared to the
control (OCC pulp sheet) after heating at 600 °C (Fig. 8). This higher
residual char points to the likelihood that soy protein isolate-
EDTA-chitosan is cross linked to the OCC pulp fibers.
The storage modulus and loss modulus both decrease with
increased temperature as shown in Fig. 9. It was observed that
the storage modulus of the soy protein isolate-EDTA-chitosan-trea-
ted OCC pulp sheet was 25–27.3% higher when the temperature
range was between 35 and 197 °C. The higher storage modulus is
likely a result from the additive treated OCC pulp sheet being more
flexible due to cross linking with the soy protein isolate-EDTA-
chitosan additive [16]. However, the loss modulus for the OCC pulp
hand sheet over the same temperature range decreased approxi-
mately 10%, while for the soy flour isolate-EDTA-chitosan addi-
tive-treated OCC pulp sheet, it decreased roughly 14%.
Fig. 9. DMA of a = Storage modulus of SF-EDTA-chitosan treated-OCC pulp hand
sheet, b = Storage modulus of OCC pulp hand sheet, c = Loss modulus of SF-EDTA-
chitosan treated-OCC pulp hand sheet, and d = Loss modulus of OCC pulp hand
sheet.
5. Conclusions
Soy protein isolate (SPI) from soy flour and its hydrolysates
from separate treatments of acid, alkali, and enzyme were studied
for their effect on OCC pulp sheet dry strength. Soy protein and
hydrolyzed soy protein isolates were modified with EDTA in the
presence of sodium hypophosphite (SHP) to increase their ability
to better bond recycled fibers during paper formation. It was found
that the carboxyl group content of modified soy protein isolate sig-
nificantly increased relative to the unmodified soy protein isolate,
a driving hypothesis for the observed strength gains. The EDTA
coupled soy protein isolate and hydrolyzed EDTA coupled soy pro-
tein isolate were later cross linked with chitosan (Ch). Approxi-
mately 2% of soy protein isolate-EDTA-chitosan and their
derivatives (acid hydrolyzed SPI-EDTA-Ch, alkali hydrolyzed SPI-
EDTA-Ch, and enzymatic hydrolyzed SPI-EDTA-Ch) were blended
with OCC recycle pulp separately before making samples. The ten-
sile and burst strengths increased 46.3%, 43.02%, 38.35%, and 27.2%,
and 61.85%, 64.56%, 57.42%, and 65.5%, respectively, compared to
Fig. 8. Thermogravimetric analyses of OCC pulp sheet and soy protein isolate-
EDTA-chitosan additive-treated OCC pulp sheets.

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A. Salam et al. / Reactive & Functional Polymers 85 (2014) 228–234
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The authors would like to cheerfully acknowledge the support
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Chemistry at NC State University (USA) and partial support of this
work from a research Grant administered by Smith-Bucklin &
Assoc., LLC, through the United Soybean Board (Internal Grant
No. 2013-0248/1340-512-5257).
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