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Karavana_06a_SC.docx ACCEPTED MANUSCRIPT 17/05/2021
Interactions between Collagen and Alternative Leather Tannages to
Chromium Salts by Comparative Thermal Analysis Methods
Thermal stabilization of collagen by tanning process
Ali Yorgancioglu
Department of Leather Engineering, Faculty of Engineering, Ege University,
35100, Bornova-Izmir, Turkey
Ersin Onem
Department of Leather Engineering, Faculty of Engineering, Ege University,
35100, Bornova-Izmir, Turkey
Onur Yilmaz
Department of Leather Engineering, Faculty of Engineering, Ege University,
35100, Bornova-Izmir, Turkey
Huseyin Ata Karavana*
Department of Leather Engineering, Faculty of Engineering, Ege University,
35100, Bornova-Izmir, Turkey
E-mail: atakaravana@gmail.com
Abstract
This study aims to investigate the interactions between collagen and tanning process
performed by Ecoltan®, phosphonium, EasyWhite Tan®, glutaraldehyde, formaldehyde-free
replacement syntan, condensed (mimosa) and hydrolyzed (tara) vegetable tanning agents
as alternative tannages to conventional basic chromium sulphate widely used in leather
industry. Collagen stabilization with tanning agents was determined by comparative
thermal analysis methods; differential scanning calorimetry (DSC), thermogravimetric
analysis (TGA) and conventional shrinkage temperature measurement. Analysis techniques
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and tanning agents were compared and bonding characteristics were commented by
thermal stabilization they provided. Chromium tanning agent was also examined to be
comparable of novel tannages for leather industry. The results were interesting as a
different perspective than the conventional view to provide a better understanding of the
relationship between tanning and thermal stability of leather materials.
Introduction
Tanning, in simple terms, refers to the treatment of raw hides/skins with
tanning materials to render the material immune to microbial degradation
through interactions (1). There are a large variety of chemicals used in the
production of many different leather types. However, the major chemicals
are the tanning agents as they define the process of leather manufacture
as a whole (2). In the tanning process; tanning agent is penetrated into the
collagen matrix and distributed evenly through cross section then it is
bounded irreversibly to the collagen reactive sites (3). It has been accepted
that the tanning ability of a substance is related with the type of the
interaction occurs between the tanning agent and collagen (4). The tanning
efficiency is conventionally defined by the shrinkage temperature (Ts) which
is the measurement of the resistance of leather to heat in aqueous medium.
Fibre bundles of collagen can be induced to undergo an abrupt decrease in
length at a characteristic shrinkage temperature when subjected to slow
heating in aqueous medium. The factors affecting shrinking include the
intramolecular interactions and the superimposed intermolecular
interactions. The latter is bought about by tanning and the sites available
for tanning vary depending on the tanning agent. If the tanning agent forms
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strong bonds as covalent, coordinative, etc., leather has high hydrothermal
stability having high shrinkage temperature values (5). The introduction of
these crosslinks produces a more regular structure, decreases the entropy
and so more energy is required to denature the collagen, hence, the
shrinkage temperature rises.
In the modern day, tanners choose tanning chemicals based on their
performance, price, ease of use, environmental issues, and their aesthetic
properties (grain, color, touch, etc.) (6). Chromium salts (commonly basic
chromium sulphate) are the most widely used tanning agents with a
utilization rate of 85% in the world owing to their low cost, high versatility
and quality of the final product obtained (7). Chromium compounds gives
high hydrothermal stability to leathers up to 100 °C with properties light in
weight and soft in touch. Beside these advantages, chromium has also
disadvantages such as low exhaustion rate from floats (70% in 24h), its
blue-greenish color, too much elasticity in some cases and possesses a risk
for formation of carcinogenic Cr+6 species from unbounded chromium (8).
In conventional chromium tanning the low exhaustion results in discharging
30% of chrome tanning agent into the wastewater (9). These disadvantages
promotes the use of more environmental friendly tanning alternatives (10).
For this purpose other inorganic tanning agents such as zirconium,
aluminum, titanium, zinc, etc., or organic tanning agents, i.e. vegetable
tannins, synthetic tannins, polyaldehydes, phosphonium salts are
commonly used alone or in combination as chromium-free or metal-free
tanning systems (11). But, it is worth noting that metal-free tanning agents
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employed for the production of “wet-white” leather have limited applications
compared to chrome tanned leather (“wet-blue”) since the physical and
mechanical characteristics of wet-white leather are generally lower
compared to wet-blue leather (12). Moreover, consumers' anxieties about
the possible damages of metals to human health and REACH restrictions on
heavy metals conduced the metal-free tanning systems to be highlighted in
the current years (13-14).
Vegetable tannins, synthetic tannins (syntans), aldehydes are some good
alternative tanning agents provide metal-free leather goods (13, 15, 16).
Some chemical companies has developed new tanning systems for chrome-
free and metal-free leathers towards sustainable leather making.
Investigations of alternative tannages to basic chromium sulphate in leather
industry and their tanning abilities with the sensitive analyses are highly
important.
As mentioned above hydrothermal stability of leather is generally
measured by observing the temperature at which the leather specimen
shrinks when heated in water at 2 oC min-1. This phenomenon is called as
shrinkage temperature (Ts) defined by the standard method ISO 3380
(IULTCS/IUP 16) (17). On the other hand, there are also alternative
analytical techniques providing information about the thermal behaviors of
tanned leathers (18-20). Fully hydrated (>200% water/collagen), native
collagen undergoes a denaturation when heated to approximately 62 °C, as
observed by shrinkage of the samples to a third of the original length, and
by the peak in measurements taken by means of differential scanning
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calorimetry/differential thermoanalysis (DSC/DTA). The peak point of the
first endothermic event observed in the DSC thermograms usually refers to
the Ts and the area below this peak corresponds to the heat requirement of
the endothermal melting process. Thermal behaviour of the tanned collagen
can be accurately measured using much smaller samples by
thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC)
methods (21). These thermal analyses are useful for fast evaluation of
thermal stability and behavior, degradation temperature, absorbed
moisture content, crystallized water content, melting point and thermal
decomposition kinetics in a closed measurement atmosphere (22).
Application of these sensitive techniques puts in more realistic evidence in
a short time using milligram quantities concerning denaturation or
deterioration degree by the phase transitions of dry biomaterial (23, 24),
especially when the daily using conditions of leather materials are
considered. Leather materials, applied in automotive, furniture, military
shoes, gloves, aircraft seating etc., required high thermal resistance must
be analyzed with the detailed techniques under the interior or exterior
extreme conditions (25). To our knowledge, only a few literature was
reported on this phenomenon by the comparative thermal behavior of
dry/wet collagen (26) and less is known about the degradation mechanism
of tanned leathers (27).
Present study aims to investigate the thermal behaviour of leathers with
various tannages via different techniques and to provide a better
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understanding of the relationship between tanning and thermal stability of
leather composed of collagen fibers.
Experimental Setup
Materials
Commercially pickled Turkish sheepskins were used for tanning operations.
Tanning agents used in the study were industrially produced, commercially
available products: chromium salts and Ecoltan tanning agents from
“Sisecam Chemicals”, Easy-white tanning agent (Granofin®Easy F-90) from
“Stahl-Turkey”, glutaraldehyde and formaldehyde free replacement syntan
from United Chemicals, tara and mimosa tannin from “Silvachimica S.r.l.”.
Ecoltan tanning agent is basic chromium sulphate with some alkali
ingredients providing higher chrome exhaustion rates and an ecological
solution with its pickle free chrome tanning process. On the other hand,
Granofin®Easy F-90 tanning system provides chrome-free tanning
technology. The main components of the Easy-white tanning agent were
synthesized by using cyanuric chloride and p-aminobenzenesulfonic acid.
Other chemicals in the production were provided from various suppliers.
Leather manufacturing processes
Tanning operations with different tanning agents were made in accordance
with a production process applied commercially in a leather factory.
Depickling process was firstly applied for all leathers in the same way before
tanning operations (Table I). Subsequent to depickling, the skins were
tanned with each type of tanning agent using the recipes given in Table II-
IX.
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Table I
Depickling recipe of the leathers
Process % Chemicals Temp. (oC) Time Remarks
(min)
Depickle 150 Water 27 20 7Bé
1 HCOONa 40 pH 4.0
1 HCOONa 45 pH 5.0, drain
Washing 200 Water 7Bé 28 10 Drain
Fleshing
Bating 100 Water
1,5 Acidic bating 35 60 Drain
enzyme
Washing 200 Water 30 Drain
Degreasing 6 Degreasing agent 28 60
50 Water 3Bé 28 90 Run overnight,
drain
Washing x 3 200 Water 30 30 Drain
Table II
Chrome tanning recipe
Process % Chemicals Temp. (oC) Time Remarks
(min)
Pickle 100 Water 30 20 6 Bé
1.5 HCOOH pH 2.8
0.1 Fungicide 20
Chrome tanning 4 Chromium salts 60
2 Synthetic fatliquor
4 Chromium salts 420
1 HCOONa 45
0.5 NaHCO3 60 pH 4.1, drain
Washing 200 Water 30 30 Drain
Horsing-Drying
Table III
Ecoltan tanning recipe
Process % Chemicals Temp. (oC) Time Remarks
(min)
100 Water 30
Ecoltan tanning 7 Ecoltan 480
2 Synthetic fatliquor
0.1 Fungicide Overnight 5
min/h
Next morning
pH 4, drain
Washing 200 Water 30 Drain
Horsing-Drying
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Table IV
Glutaraldehyde tanning recipe
Process % Chemicals Temp. (oC) Time Remarks
(min)
100 Water 30
12 Glutaraldehyde 30 60
3 HCOONa 30
Aldehyde 7 Glutaraldehyde 90
tanning
2 Synthetic fatliquor
1 HCOONa 45
1.5 NaHCO3 60 pH 8, Rest
overnight,
drain
Washing 200 Water 30 Drain
Horsing-Drying
Table V
Formaldehyde free replacement syntan tanning recipe
Process % Chemicals Temp. (oC) Time Remarks
(min)
Pickle 150 Water 30 20 7 Bé
1 HCOOH pH 3.7
2 Synthetic fatliquor 45
0,5 H2SO4 60 pH 3,1
0.1 Fungicide 30
Syntan tanning 15 Syntan 120
10 Syntan 180 pH 3,5,
Overnight
100 Water 40
1 HCOOH 30 pH 3.2, drain
Horsing-Drying
Table VI
Easy-white tanning recipe
Process % Chemicals Temp. (oC) Time Remarks
(min)
200 Water 28
1 HCOONa 30 pH 5,5
2 Synthetic fatliquor
Easy-white 10 Granofin F-90 Run overnight
tanning
50 Water 45 60
50 Water 50 90 Drain
Horsing-Drying
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Table VII
Tara tanning recipe
Process % Chemicals Temp. (oC) Time Remarks
(min)
Pickle 150 Water 30 20 6 Bé
0.7 HCOOH pH 4.2
Tara tanning 2 Dispergator 20
10 Tara 30
1 Synthetic fatliquor 30
5 Tara 30
1 Synthetic fatliquor 30
5 Tara 30
0.5 HCOOH 2x30 pH 3.8, drain
Horsing-Drying
Table VIII
Mimosa tanning recipe
Process % Chemicals Temp. (oC) Time Remarks
(min)
Pickle 150 Water 30 20 6 Bé
Mimosa tanning 2 Naphthalene syntan 20
10 Mimosa 30
1 Synthetic fatliquor 30
5 Mimosa 30
1 Synthetic fatliquor 30
5 Mimosa 30
1.5 HCOOH 2x30 pH 3.6, drain
Horsing-Drying
Table IX
Phosphonium tanning recipe
Process % Chemicals Temp. Time Remarks
(oC) (min)
Pickle 80 Water 30
12 Salt 20 6 Bé
0.5 HCOOH pH 4.0
1 Synthetic oils and 45
esters
Phosphonium 10 THPS 90
tanning Tetrakis(hydroxyme
thyl)phosphonium
sulfate
1 Synthetic oils and
esters
1 Synthetic fatliquor 20
1 HCOONa 45
0.5 NaHCO3 60 pH 5.2, drain
Horsing-Drying
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Determination of shrinkage temperature
The measurement of the shrinkage temperature (Ts) of the leathers was
performed according to the IUP 16 standard test method. The basic principle
of the method is to suspend the leather test sample in water under heating
2 °C min-1 and to note the temperature when it starts to shrink visibly (28).
Differential scanning calorimetry (DSC) analysis
Differential scanning calorimetry (DSC) measurements were carried out on
the tanned leathers to determine the denaturation temperatures (Td) using
a Shimadzu DSC-60 Plus instrument. DSC analyses of tanned leathers were
conducted at a heating rate of 10 °C min-1 under nitrogen atmosphere
(purity 99.99%, flow 20 mL min-1). Leather samples were heated from 25
to 250 °C in a hermetic pan, which was covered with an aluminum lid with
two small holes. Sample mass was approximately 5 mg in dry form. The
reference had a similar empty crucible.
TGA analysis
Thermal analysis with TGA method was carried out on different tanned
leathers using Perkin Elmer TGA 8000 instrument. The leather samples were
weighed between 3-5 mg in ceramic pans and the flow rate of nitrogen gas
(99.99% purity) in the system was set at 20 mL min-1. The analysis of the
samples was performed between 30-800 oC with a heating rate of 10 oC
min-1. Main degredation process of the samples was observed with the peak
points obtained by thermogravimetric (TG) and derivative thermal
gravimetry (DTG).
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Results and Discussions
Tanning means converting the rawhide or skin, a highly putrescible
material, into leather, a stable material. In this process the different kinds
of bonds are replaced with tanning agents like chromium, aluminium or
other mineral salts, vegetable or synthetic tanning agents to stabilize the
material and to protect it against microbial attack. In the tanning process
the collagen fibre is stabilised by the cross-linking action of the tanning
agents such that the hide (pelt) is no longer susceptible to heat increases.
The level of susceptibility to heat changes with the tanning system. In the
study the leathers tanned with eight different widely used tanning agents
were evaluated with their thermal behavior using conventional shrinkage
temperature measurement, DSC and TGA. The results are given in Table X
and Fig. 1-5. Examining the relationship between denaturation
temperatures and shrinkage temperatures, it was clear that there was a
correlation between the Ts and Td values obtained from both methods as
previously observed (3). Although there were small difference of
temperature values the denaturation temperature and shrinkage
temperature had the same increasing tendency.
From the results, we can see that the highest Ts and Td results were
obtained from chromium tanned leathers. The shrinkage temperature of
chrome tanned leathers in the control group was measured as 103.5 °C,
and the denaturation temperature as 97.6 °C. Similarly, Ecoltan tanning as
a model of chrome tanning process provided 96.5 °C shrinkage temperature
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and 97.4 °C denaturation temperature to the leather. Ecoltan tanning is one
of the innovative model providing higher chrome exhaustion rates and an
ecological solution with its pickle and basification free chrome tanning
process. The binding mechanism of these two tanning is through
crosslinking at the carboxylate side chains of collagen with coordinated
covalent bonds. The stability of the chrome-collagen complexes formed in
this manner is characterised by the shrinkage temperature, which is one of
the most important criteria in determining the overall hydrothermal stability
of leathers (29). Chrome tanned collagen is resistant to boiling water
typically up to 95-100 °C, thus indicating formation of high hydrothermally
stable crosslinks within the structure.
Following the chromium, the highest Ts/Td values were obtained from
phosponium-tanned leathers among the metal-free tanning systems as
expected. It is the fact that THPS can form short and strong cross bonds
mostly with amino groups and less with hydroxyl and carboxyl groups and
peptide bonds of collagen in leather. It is also reported that THPS would be
converted into tri-hydroxymethyl phosphonium (TrHP) and tri-
hydroxymethyl phosphine oxide (TrHPO) during the tanning process. The
nucleophilic substitution between formaldehyde and amino groups of
collagen takes place during the reaction. The hydroxylmethylated amino
groups of collagen combine with highly reactive phosphorus in TrHPO. The
hydroxylmethyl groups of TrHPO combined with collagens dissociate
continuously and nucleophilic reaction between formaldehyde and amino
groups of collagen take place, too. Therefore, combination between
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hydroxylmethylated amino groups and phosphorus results in a large
number of cross-links in collagen fibers and accomplishes the tanning
process which results with high thermal stability (30, 31).
The other Ts/Td values obtained from metal-free tannages were in the
decreasing order of aldehyde, mimosa, tara, EasyWhite Tan® and syntan.
As giving the second highest shrinkage value, glutaraldehyde is the most
known aldehyde tanning agents shown to be the most versatile and widely
used, especially in automotive upholstery and upper leathers (32). The
aldehyde functional group forms covalent bonds with nonionised amino
side-chains of collagen. During this interaction schiff bases can be
synthesized from collagen amine sites and a carbonyl compound of
aldehyde. It also forms semiacetal bonds with the hydroxyls of
hydroxyproline, hydroxylysine, and serine (33).
The tanning mechanism of vegetable tannins or natural polyphenols are
due to the formation of numerous hydrogen bonds with collagen basic
groups, e.g. lysine and arginine and peptide backbone. Due to the high
number of hydrogen bonding they have higher Td/Ts values following
aldehydes. The tanning efficiency was higher for condensed tannin
(mimosa) than hydrolyzed one (Tara) as expected (21, 34, 35).
Easy-white tanning system is started to be used as a new technology in
the leather processing, a completely chromium-free tanning method. The
method was told to offer numerous benefits by helping to meet the growing
needs for chromium-free leather processing. Although its tanning
mechanism is not exactly explained it is assumed to be based on hydrogen
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bonding and bonding of active chlorine of triazine ring in the molecule
reacting with the amino groups of collagen fiber since it gives Td/Ts values
close to syntans. On the other hand, replacement syntan tanned leather
had the lowest shrinkage values as expected. During the tanning process;
the ionised sulfonic acid groups of the syntans have strong ionic attraction
for the cationic amino functional groups on the collagen side chains, while
the phenolic structures bind similarly to vegetable tannins via hydrogen
bonds, however, lower in number of bonding sites (36-38).
Table X
Ts and Td values of the leathers
Leather samples Ts, oC DSC/Td, oC
Chrome tanned (control) 103.5 97.6
Ecoltan tanned 96.5 97.4
Phosphonium tanned 88 93.2
Aldehyde tanned 83.5 88.9
Mimosa tanned 79 86.1
Tara tanned 77.5 84.6
Easy-white tanned 75.5 79.0
Syntan tanned 74 82.6
DSC thermograms of different tanned leathers were shown in Fig. 1. As can
be seen in the figure it is observed that the leathers processed with different
tanning agents had similar thermograms having one endothermic peak.
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Fig. 1. DSC curves of different tanned leathers
TGA is one of the simplest and practical techniques used to characterize the
thermal stability of materials by monitoring the change in weight as a
function of increasing temperature, or isothermally as a function of time, in
a controlled atmosphere (nitrogen, oxygen, air, etc.). This information helps
us identifying the percent weight change and correlate chemical structure,
processing, and end-use performance of material (39). The mass evolutions
with temperature of tanned leathers were shown in Fig. 2-5, DTG curves at
Fig 6 and Table 11 indicating the peak temperatures of derivatives. Almost
all samples displayed similar behavior indicating two degredation steps
within the temperature range of 20 °C-800 °C. The first step of mass loss
observed up to 100 °C was due to the loss of free and bound water within
the samples. The main degredation step was observed between 230 °C-450
°C which indicates decomposition of proteinic material. However, the
thermal behavior of the leathers was different in dry condition than in
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aqueous one. Among the all samples syntan and mimosa tanned leathers
showed higher thermal stability than other leathers regardsless from their
shrinkage temperatures. Similarly, phosphonium tanned leather also
showed high thermal stability. The reason for syntan and mimosa tanned
leather can be due to their poor thermal conductivity and high thermal
stability of phenolic and aromatic structures. This kind of substances is used
in the compositions for preparation of fire retardant materials and/or
polymers. Similarly, phosponium based compounds are also well known as
good fire retardants thus, increasing the thermal stability of materials. The
chromium tanned leathers (Chromium and Ecoltan) had high peak
temperatures (337 and 325 °C) where the maximum degredation process
took place, however, their degredation process seemed to be fast with high
burn off ratio and low ash amount. This may be explained due to the
increased thermal conductivity of these leathers since chromium as a metal
may dissipate the heat efficiently through the proteinic material resulting in
fast degredation process. Tara tanned leather showed a fast degredation
with an early onset temperature possibly due to the hydrolysis of ester
groups in its structure. Moreover, gluteraldehyde and tara tanned leathers
also showed a third degredation step after 500 oC leading to a high degree
of degredation that can be due to their high organic content, however seems
to be further investigated.
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Fig. 2. TGA curves of all tanned leathers
Fig. 3. Comparison of the TGA curves of syntan, mimosa, tara and EasyWhite Tan®
tanned leathers
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Fig. 4. Comparison of the TGA curves of syntan, Ecoltan and chromium tanned leathers
Fig. 5. Comparison of the TGA curves of syntan, gluteraldehyde and phosponium tanned
leathers
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Fig. 6. DTG curves of all tanned leathers
Table XI
TGA outputs from TG and DTG curves
Leather samples Peak Total mass loss (%) at
temperatures of 800 oC
derivatives, oC (without water
(Tpeak) content)
Chrome tanned (control) 337.7 75.3
Ecoltan tanned 325.2 70.2
Phosphonium tanned 328.3 60.7
Aldehyde tanned 309.3 86.4
Mimosa tanned 321.6 58.3
Tara tanned 315.5 84.4
Easy-white tanned 325.6 71.1
Syntan tanned 336.5 58.3
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Conclusion
Thermal stability and decomposition kinetics of the collagen-based
materials are the critical for the quality control parameters of final and
tanned leather products as well. The TG-DTG and DSC techniques proved
to be straightforward experimental methodology to achieve efficient data
on the dry leather materials by giving more precision and sensitivity
compared to the conventional shrinkage temperature which measures the
hydrothermal stability of collagen.
The relationship between denaturation temperatures and shrinkage
temperatures was clear as a correlation from the applied methods. There
were small difference of temperature values, while the denaturation
temperature and shrinkage temperature had the same increasing tendency.
On the contrary to the shrinkage performance the chromium and Ecoltan
tanned leathers indicated lower thermal stability than other leathers. This
may be explained due to the increased thermal conductivity of these
leathers since chromium as a metal may dissipate the heat efficiently
through the proteinic material resulting in fast degredation process. It is
interesting to see that the leathers having lower shrinkage temperature may
have the higher thermal stability, provided by syntan and mimosa, due to
their poor thermal conductivity. The findings have potential as a notable
literature for the leather industry players, readers and the scientists to
comprehend the proper thermal behavior of the final leather products.
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References
1. M. Sathish, A. Dhathathreyan and J.R. Rao, ACS Sustain. Chem. Eng.,
2019, 7, 3875.
2. A.D. Covington, “Tanning Chemistry, The Science of Leather”, The
University of Northampton, Northampton, UK, 2009.
3. E. Onem, A. Yorgancioglu, H.A. Karavana and O. Yilmaz, 2017, J.
Therm. Anal. Calorim., 2017, 129, 615.
4. A.D. Covington, A. D., “The Chemistry of Tanning Materials”, In: Kite,
M. & Thomson, R.,(eds.). Conservation of leather and related materials.
Oxford: Butterworth-Heinemann, 2006.
5. Q. Yao, Y. Wang, H. Chen, H. Huang and B. Liu, ChemistrySelect,
2019, 4, 670.
6. N. Ork, H. Ozgunay, M.M. Mutlu and Z. Ondogan, Tekst. Konfeksiyon,
2014, 24, 413.
7. UNIDO, Future Trends in the World Leather and Leather Products
Industry and Trade, 2010.
8. S. Scopel, C. Baldasso and A. Dettmer, J. Am. Leather Chem. As.,
2018, 113, 122.
9. M. Renner, E. Weidner and H. Geihsler, J. Am. Leather Chem. As.,
2013, 108, 289.
10. G. Krishnamoorthy, S. Sadulla, P.K. Sehgal and A.B. Mandal, J. Clean.
Prod., 2013, 42, 277.
11. H.A. Karavana, B. Basaran, A. Aslan, B.O. Bilisli and G. Gulumser,
Tekst. Konfeksiyon, 2011, 21, 305.
21
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Doi: 10.1595/205651322X16225583463559Karavana_06a_SC.docx ACCEPTED MANUSCRIPT 17/05/2021
12. Y. Dilek, B. Basaran, A. Sancakli, B.O. Bitlisli and A. Yorgancioglu, J.
Soc. Leath. Tech. Ch., 2019, 103, 129.
13. R. Aravindhan, B. Madhan and J.R. Rao, J. Am. Leather Chem. As.,
2015, 110, 80.
14. V. Beghetto, L. Agostinis, V. Gatto, R. Samiolo and A. Scrivanti, J.
Clean. Prod., 2019, 220, 864.
15. K.J. Sreeram, R. Aravindhan, J.R. Rao and B.U. Nair, J. Am. Leather
Chem. As., 2010, 105, 401.
16. V.J. Sundar and C. Muralidharan, Environ. Process, 2020, 7, 255.
17. J.M.V. Williams, J. Soc. Leath. Tech. Ch., 2000, 84, 359.
18. T. Bosch, A.M. Manich, J. Carilla, J. Cot, A. Marsal, H.J. Kellert and
H.P. Germann, J. Am. Leather Chem. As., 2002, 97, 441.
19. P. Budrugeac, V. Trandafir and M.G. Albu, J. Therm. Anal. Calorim.,
2003, 72, 581.
20. Y. Wang, J. Guo, H. Chen and Z. Shan, J. Therm. Anal. Calorim., 2010,
99, 295.
21. C. Carşote, E. Badea, L. Miu and G. Della Gatta, J. Therm. Anal.
Calorim., 2016, 124, 1255.
22. L. Yang, Y. Liu, Y. Wu, L. Deng, W. Liu, C. Ma and L. Li, 2016, J.
Therm. Anal. Calorim., 2016, 123, 413.
23. P. Budrugeac, J. Therm. Anal. Calorim., 2015, 120, 103.
24. K.M. Nalyanya, R.K. Rop, A.S. Onyuka, T. Kilee, P.O. Migunde and
R.G. Ngumbu, J. Therm. Anal. Calorim., 2016, 126, 725.
22
Johnson Matthey Technol. Rev., 2022, XX, (y), aaa-bbb
Doi: 10.1595/205651322X16225583463559Karavana_06a_SC.docx ACCEPTED MANUSCRIPT 17/05/2021
25. W. Xu, J. Li, F. Liu, Y. Jiang, Z. Li and L. Li, J. Therm. Anal. Calorim.,
2017, 128, 1107.
26. L. Rosu, C.D. Varganici, A.M. Crudu and D. Rosu, J. Therm. Anal.
Calorim., 2018, 134, 583.
27. P. Yang, X. He, W. Zhang, Y. Qiao, F. Wang and K. Tang, J. Therm.
Anal. Calorim., 2017, 127, 2005.
28. ISO 3380 Leather – Physical and Mechanical Tests – Determination of
Shrinkage Temperature up to 100 oC, 2015.
29. K.H. Gustavson, The Chemistry and Reactivity of Collagen. New York:
Academic Press Inc, 1965.
30. L. Ya, Z.H. Shan, S.X. Shao and K.Q. Shi, J. Soc. Leath. Tech. Ch.,
2006, 90, 214.
31. S. Shuangxi, S. Kaiqi, L. Ya, Y. Lan and M. Chun'an, 2008, Chin. J.
Chem. Eng., 2008, 16, 446.
32. R. Li, Y.Z. Wang, Z.H. Shan, M. Yang, W. Li and H.L. Zhu, J. Soc.
Leath. Tech. Ch., 2016, 100, 19.
33. V. Plavan, M. Koliada and V. Valeika, J. Soc. Leath. Tech. Ch., 2017,
101, 260.
34. C. Claudio, G. Fausto and P. Vincenzo, Asia Pac. J. Chem. Eng., 2011,
6, 606.
35. Z. Sebestyén, E. Jakab, E. Badea, E. Barta-Rajnai, C. Şendrea and Zs.
Czégény, J. Anal. and Appl. Pyrol., 2019, 138, 178.
36. S.V. Kanth, G.C. Jayakumar, S.C. Ramkumar, B. Chandrasekaran,
J.R. Rao B.U. and Nair, J. Am. Leather Chem. As., 2012, 107, 142.
23
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Doi: 10.1595/205651322X16225583463559Karavana_06a_SC.docx ACCEPTED MANUSCRIPT 17/05/2021
37. E. Onem, G. Gulumser, M. Renner and O.Y. Celiktas, J. Supercrit.
Fluid., 2015, 104, 259.
38. R. Saleem, A. Adnani and F.A. Qureshi, Indian J. Chem. Techn., 2015,
22, 48.
39. P. Budrugeac, A. Cucos and L. Miu, J. Therm. Anal. Calorim., 2014,
116, 141.
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The Authors
Ali Yorgancioglu is working as a research assistant in the
Leather Engineering Department of Ege University,
Engineering Faculty. He has a PhD degree in the field of
leather engineering and been in Fraunhofer-Institute
UMSICHT, Germany for his PhD thesis. He assisted
“Tanning Technologies”, “Leather Auxıliary” and
“Chemistry” courses. He teaches “Raw Hide” and
“Leather Histology” courses in the Bachelor’s degree. He
has participated in various national projects as
researcher. His research activities and fields of interests
are emulsions, nanotechnology, leather fatliquors,
tanning technologies and cleaner leather technologies.
Ersin Onem graduated from Ege University Engineering
Faculty, Department of Leather Engineering in 2006. He
received his MSc degree in the same department in
Izmir, Turkey. After MSc degree, he worked in the TFL
laboratories for a while. He cooperated with Fraunhofer
Institute on the CO2 ambient for sustainable production
in leather industry by using supercritical fluid technology
and finished his PhD in 2015. After PhD, he attended to
European Union Project in Germany for 9 months as
post-doctoral studies. Onem currently serves as
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Associate Professor in the Department of Leather
Engineering in Ege University. His research interests are
on tanning technologies, ecological production,
environmentally friendly processings, supercritical fluid
applications and high pressure technologies.
Onur Yılmaz has been working as an associated professor
at Leather Engineering Derpartment in Ege University
since 2015. He graduated from Ege University
Engineering Faculty, Department of Leather Technology
in 2002. He finished his MSc studies in Enviromental
Sciences Department in Ege Üniversity. He made his PhD
studies in collaboration with Petru Poni Institute of
Macromolecular Chemistry in Iasi-Romania and
completed his pHD in Leather Engineering Department,
Ege University in 2011. He continued his postdoctoral
studies in Laboratory of Polymers in Chemistry
Department of Helsinki University between 2012-2014.
His research interest are enviromentaly friendly systems
in leather technology, polymer synthesis,
nanocomposites, acrylates, coating and finishing
systems.
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Hüseyin Ata Karavana graduated from the Leather
Technology Department, Faculty of Agriculture, Ege
University, Turkey. He earned his MSc degree in Leather
Technology in 2001 from that institution’s Graduate
School of Natural and Applied Science. From 2006 to
2007 he continued his studies as an Erasmus student in
the Department of Footwear Engineering and Hygiene at
the Tomas Bata University’s Faculty of Technology (Zlin,
Czech Republic). Karavana completed his PhD degree in
Leather Engineering at Ege University in 2008. Karavana
currently serves as Associate Professor in the
Department of Leather Engineering at Ege University’s
Faculty of Engineering. His research interests are in all
manner of leather and footwear engineering including
plastic composites, microencapsulation, leather quality
and control, footwear quality and control.
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