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A Technical Paper presented at the 110th annual meeting of the American Leather Chemists
Association at the Pinehurst Resort, North Carolina on 10th June 2015
INVESTIGATING THE CELL ROTARY CONDITIONING
MECHANISM USING DYNAMIC MECHANICAL THERMAL
ANALYSIS.
K. B. FLOWERS*1, A. PERUZZI2, W. R. WISE1, AND A.D. COVINGTON1
1The University of Northampton, Park Campus, Boughton Green Road, Northampton, NN2 7AL, UK
2IST and Fratelli Carlessi, Via Ferraretta, 48 36071 Arzignano (VI), Italy
ABSTRACT
Jeyapalina et al. established that dynamic mechanical thermal analysis (DMTA) can be used
to gauge the progression of leather drying1. This work has now been advanced in order to
understand the mechanism surrounding sorption/desorption of moisture during cell
conditioning, e.g., cell rotary conditioning (CRC). This paper will demonstrate how the use
of DMTA could be used to monitor changes in leather stiffness. A gravimetric moisture
analysis was performed on identical leather samples to gauge the progression of desorption.
The change in storage modulus (E’) was coupled to the moisture content (leather moisture
and atmospheric relative humidity) to obtain a better understanding of the physical properties
(specifically stiffness) of leather during a drying process. The research presented illustrates
how DMTA can indicate leather fibre response to changes in atmospheric humidity and
facilitate real-time adaptation of drying conditions during leather dehydration. The use of a
cell conditioning system allows a tanner to control the flexibility of the material through: the
tension applied and the drying conditions. DMTA shows that the favourable conditions inside
a CRC unit result in detectable changes to the leather fibre, similar to findings by
Abrahamson and Williams-Wynn2. Using this technique a researcher can dry chromium-
containing and chromium-free leathers in a manner that is highly customisable to produce
desired physical properties. Difficulties experienced in chromium-free leathers can also be
investigated in detail using this technique3.
INVESTIGATING THE CELL ROTARY CONDITIONING MECHANISM USING DYNAMIC MECHANICAL ANALYSIS.
K. B. FLOWERS*1, A. PERUZZI2, W. R. WISE1, AND A.D. COVINGTON1
2.
INTRODUCTION
Drying literature
Drying literature within the leather industry is divided into three main eras where the
emphasis is placed on different topics that were relevant to the technology at the time. In the
1930s and 40s the research focussed on shoe comfort and the movement of water (as vapor)
through the leather substrate. From 1950-70 the emphasis was on trying to determine the
simultaneous flow of heat and moisture, into/out of leather, in the hopes of modelling drying
so that tanneries could optimize their drying parameters. The research is well summarized in
Lamb et al.4. From 1990 to 2015, Liu et al. worked to understand the mechanism of drying
and the resulting leather physical properties5-13. Liu et al. established a mathematical model
in low pressure conductive drying that is given in Equation 1 that allows a tannery to predict
their vacuum drying rates from their drying parameters14,15.
Where K is a drying constant based on the leather type (K = 0.17 for chromium-containing
leathers14; K = 0.32 for chromium-free); Wo is the initial water content; T is the drying
temperature and Tb is the boiling point of the water; d is the thickness of leather; t is the
drying time and f is the amount of fatliquor (as fraction of tanned hide mass).
Lamb illustrates (see Figure 1) a drying profile of leather, a hygroscopic and porous
material16,17. From the figure, one can see a constant drying rate followed by two or more
variable drying rate periods.
Figure 1. Starting with constant rate drying, the curve moves into the first variable rate drying sequence that is lower than the
first phase of drying. A slower third phase of drying shows a marked tailing of the drying rate that is often attributed to
removal of bound water 16.
INVESTIGATING THE CELL ROTARY CONDITIONING MECHANISM USING DYNAMIC MECHANICAL ANALYSIS.
K. B. FLOWERS*1, A. PERUZZI2, W. R. WISE1, AND A.D. COVINGTON1
3.
It is commonly understood that during constant rate drying (first-phase drying) the
mechanism of water removal is evaporative and is rate-governed by the: water-carrying
capacity of the air; surface area of drying interface; and replenishment rate of water to the
leather surface (see Equation 2). Water-carrying capacity is affected by temperature, the
relative humidity and the flow speed of air over the leather18.
Replenishment rate of the water at the drying surface is affected by the surface area requiring
that water, the porosity of the leather and the tortuosity factor of the leather. If a high
replenishment is required the force of the capillary action may result in a rapid narrowing
(shrinkage) of the fibre spaces19,20. Humphreys considers this to be highly detrimental in the
processing of not only thick, but also vegetable tanned leather21.
Where dW/dθ is the rate of drying, h is the heat transfer coefficient, A is the surface area, T is
the temperature difference between the surface and air stream and λ is the latent heat of
evaporation21,22.
In convection drying, evaporation dominates the mechanism. Evaporation is a vaporisation
process that takes place at air/liquid interfaces23. Inside a liquid, vaporisation can only take
place if the vapor pressure of the liquid is greater than the atmospheric pressure (as is
commonly the case in boiling). Evaporation at the leather surface will result in movement of
liquid from the inside out until the rate of replenishment cannot match the rate of evaporation.
Movement of liquid, governed by Fick’s second law of diffusion, is mainly through
interfibrillary spaces, but 1-3% of water does move through the fibres themselves24.
As the evaporative surface recedes into the leather structure the surface area available for
evaporation rapidly increases. Possibly, the rate of drying would then increase, were it not
due to the fact that evaporation is slowed down by slow moisture transfer rates out of the
leather capillary structure. Variable rate or falling rate drying is typified by slow internal
evaporation. During drying, water can be re-absorbed onto the fibre because water
vaporisation is an equilibrium phenomenon.
Drying Methods
The drying of leather is largely divided into three main types and combinations of those main
types are common industrial practice. Convective, conductive and radiation type drying
methods are now universal throughout the industry with a lot of focus on the conductive
drying methods due to the short drying times they provide.
INVESTIGATING THE CELL ROTARY CONDITIONING MECHANISM USING DYNAMIC MECHANICAL ANALYSIS.
K. B. FLOWERS*1, A. PERUZZI2, W. R. WISE1, AND A.D. COVINGTON1
4.
Vacuum drying of leather is the most typical conductive system25. Toggle drying, hang
drying and suspension drying being the most common convective type of drying26-28.
Paste drying is a typical hybrid drying method where the grain of the leather is glued to a hot
plate. Conductive heat transfer takes place from the plate to the leather as well as convective
drying taking place from the flesh side.
Recently, the industry has paid attention to the use of conditioning systems at the end of
drying to ensure the moisture content is uniform across the leather substance. CRC is a hybrid
technology that couples elements of toggle drying together with leather conditioning29. The
drying method allows the simultaneous drying and conditioning under tension to achieve a
variety of leathers, with very comparable drying times.
Cell rotary conditioning exhibits major advantages in drying as the leather is contained in a
drying cell with highly defined conditions and can be held at differing degrees of tension
during the drying/conditioning cycle.
The degree of tension, i.e., the amount of strain (that may be translated into set) is achieved
using various methods, ranging in descending order of set from paste, toggle, vacuum,
hang/suspension and all will result in very different physical properties in the final leathers.
Sorption/Desorption of water
Models of interface adsorption and its corollary (evaporation) are vital in understanding
drying rates and is best described using either one of the two models: the Brunauer, Emmet
and Teller sorption isotherm equation (BET) and the Guggenheim, Anderson and de Boer
sorption equation (GAB). BET and GAB sorption profiles indicate how moisture interacts
with collagen and provide an inverse model of how drying proceeds30. If a dry fibre starts to
take up moisture, the most active sites of the collagen will take on water first and this will
give off a large amount of energy in the process. Heats of wetting for the most active groups
of the collagen at 0% moisture give off 167 J/g for vegetable tanned and 96 J/g for chromium
containing leathers31,32. Conversely, when water is desorbed it pulls energy from the drying
boundary layer and the surface cools. The surface of the leather is always significantly cooler
than the surrounding air.
Effects of heat and moisture on leather
The simultaneous movement of heat and moisture has been studied in depth by various
authors to investigate the optimal conditions for shoe leather lasting33-37. At low moisture
INVESTIGATING THE CELL ROTARY CONDITIONING MECHANISM USING DYNAMIC MECHANICAL ANALYSIS.
K. B. FLOWERS*1, A. PERUZZI2, W. R. WISE1, AND A.D. COVINGTON1
5.
contents, leathers follow Henry’s theory of coupled diffusion, with heat penetrating in two
waves38. Henry’s model is unhelpful at high moisture values.
Attenburrow relates the material science features of leather to the rheological performance of
a block copolymer, in which there are crystalline and amorphous regions39. It has been
established that collagen does exhibit a glass transition temperature (Tg): above the Tg, the
structure is more relaxed, so that area and softness are increased. Water as a plasticizer has
the effect of lowering the Tg in collagen as it does in other hygroscopic polymers. Jeyapalina
et al. showed that tanning (and retanning) materials (especially fatliquor and vegetable
tannins) also plasticize the collagen2.
Komanowsky investigated the changes occurring in leather during drying and confirmed the
relationship between shrinking during drying and the moisture content: he showed that a
critical point occurs at about 50% moisture (on wet weight basis), when linear fibre shrinkage
is initiated19. As shrinking proceeds, the fibre structure collapses to a greater and greater
extent, eventually causing the elements of the structure to approach closely enough to allow
the formation of new crosslinks by means of several reactions, including the Maillard
reaction40.
Dynamic mechanical thermal analysis
Collagen exhibits viscoelastic properties, i.e., it can be modelled as a mixture of elasticity (E’
-associated with energy storage) and viscous liquid (E” - associated with heat loss)41. Tan δ is
the damping of the sample, i.e., the dissipation of energy during a cyclic load (E’’/E’)42.
Jeyapalina et al. addressed the effects of drying leather under different conditions using
dynamic mechanical thermal analysis (DMTA). This work was able to define a generic
drying curve, in which there are critical tan δ inflections: drying to about 60% moisture on
wet weight of collagen content caused an increase in tan δ, as the bulk or freezeable water is
removed, drying to about 30% moisture on wet weight of collagen content caused a decrease
in tan δ as partially associated water is removed, further drying by removing the associated
water caused an increase in tan δ2. The scale of inflections are independent of tanning
chemistry and rate of drying, however it shows that the viscoelasticity of leather is lower if
drying is conducted under conditions of controlled humidity.
Properties of leather after drying
Liu in a number of papers examined the physical properties of chromium-free and chromium
containing leathers7-9,15. The research also looked at the properties of the leathers produced by
INVESTIGATING THE CELL ROTARY CONDITIONING MECHANISM USING DYNAMIC MECHANICAL ANALYSIS.
K. B. FLOWERS*1, A. PERUZZI2, W. R. WISE1, AND A.D. COVINGTON1
6.
differing drying methods3,5,6,9,10,12,13. Fibre separation by any means whether it is liming,
bating, over-drumming, solvent drying, staking, milling, or slow drying will result in leather
with a low apparent density.
High apparent density, from whatever cause, results in lower flexibility; variable elongation
at break; higher Young’s modulus and higher toughness. Liu and McClintick showed that
toughness has a strong correlation with fracture energy5. Brittle leather that often results from
rapid drying, has fibres that may be strong but has fibres glued together in tight bundles (high
compactness).
Fast drying methods will increase the compactness, especially if the capillary force during
drying is high, but if combined with high drying tension will result in low angle of weave and
possibly low apparent density. Wang and Attenburrow reported poor physical properties in
goatskins that had low apparent density43. Collapsed structures, loss of thickness and loss of
area are also associated with harsh drying conditions13.
Loose grain can result from many reasons, including migration of lubricants to the grain
junction, especially stable oils (e.g., sulfited fatliquors). Another source of loose grain caused
by drying could be a result from over-tension during drying (especially at <30% moisture
content) and harsh drying conditions, e.g., high drying temperature and low humidity.
Liu et al. established that high residual moisture content in leather after drying gave rise to a
higher loss of area15. It is well established that the area of leather is highly dependent on the
moisture content44. However, it is less well understood how the area of leather can be
controlled and maximised by the way in which the leather is dried. It has been shown that
area can be gained and retained by stretching leather in the wet and warm state45-47: this is
different to the retention of ‘set’, obtained by drying leather under tension39, and is the basis
of the current interest in wet staking.
The aim of this work was to examine whether viscoelasticity (using the DMTA) could be
used as an indicator of the progression of drying. The change in stiffness (using storage
modulus), while simultaneously checking the gravimetric moisture content, allowed
conclusions to be drawn about drying rates.
INVESTIGATING THE CELL ROTARY CONDITIONING MECHANISM USING DYNAMIC MECHANICAL ANALYSIS.
K. B. FLOWERS*1, A. PERUZZI2, W. R. WISE1, AND A.D. COVINGTON1
7.
EXPERIMENTAL
Leather Raw Materials
The leathers used in this research were obtained from domestic upholstery processes
currently in use in Italy. The bovine hide was of European origin. The samples were sourced
from one hide to eliminate inter-hide variation. A hide was taken through a conventional
beamhouse, which included lime-splitting, and was processed to pickle. The hide was sided at
the pickle stage and was sent to different drums for tannage, either by chromium or by
glutaraldehyde/ syntan tannage.
After tannage the hide was further cut into quarters. A chromium-containing and chromium-
free quarter were treated with fungicide and sealed (damp) in plastic bags for storage and
transportation. The remaining quarters were treated using separate post tannage recipes. After
the respective post tannage treatments, the quarters were treated with fungicide, sealed
(damp) in plastic bags and transported to ICLT for analysis. The post tannage of each quarter
had different quantities of syntan and fatliquor to suit the type of tannage.
ICLT re-split the tan-only quarters to 1.2 to 1.4 mm to make them more uniform in thickness.
The post tanned quarters were not split upon arrival. The official sampling position on the
four quarters was ascertained using BS EN ISO 2418:200248. Samples 5mm x 300mm were
clicked out (parallel to the backbone) and then conditioned in different environments that
differed only in relative humidity.
Conditioning
The wet moisture content of leather can be manipulated by the relative humidity of the
atmosphere in which the leather is stored. Saturated solutions of salts have been used to
maintain an atmosphere (above them) of known relative humidity (RH). Solutions have been
used in a range of applications from biological49 to leather50.
Table I shows how the four conditioning atmospheres were constructed to ensure leathers of
varying moisture content were prepared. The relative humidity of the atmosphere was
checked using of a Fischer hair hygrometer, model no. 111 (Feingerätebau K. Fischer GmbH,
Drebach, Germany). The cabinet atmosphere was circulated using fans.
INVESTIGATING THE CELL ROTARY CONDITIONING MECHANISM USING DYNAMIC MECHANICAL ANALYSIS.
K. B. FLOWERS*1, A. PERUZZI2, W. R. WISE1, AND A.D. COVINGTON1
8.
TABLE I
The cabinet conditions of leather samples prior to testing showing the saturated salt (or
water) used to ensure that atmosphere and the relative humidity of that atmosphere.
Relative Humidity of Atmosphere (%RH)
Solution used
45
K2CO3.2H2O (8.10 mol.dm-3)
76
NaCl (6.14 mol.dm-3)
98
KNO3 (3.13 mol.dm-3)
Analytical grade salts were used (Fisher Scientific, Loughborough, UK). Basins of the
saturated solutions were placed into the conditioning cabinets and the atmospheres allowed to
equilibrate for a week before sample testing commenced.
The samples for testing were placed in the humidity chambers and allowed to equilibrate for
a week. Weights before and after conditioning were measured. Leather samples from each
pre-condition atmosphere were dried according to BS EN ISO 4684:2005 to check the
volatile content of the leather51. The volatile content of the leather comprises a number of
chemicals that would be removed by drying at 105°C for 8 hours, but the majority would be
water and for the sake of simplicity, this research refers to the removed volatile components
as water.
BS EN ISO 4684:2005 calculates the volatile content, according to Equation 3 which
expresses the leather on a wet-basis, whilst the volatile content of this research is expressed
on a wet-basis as calculated from Equation 3.
Where M1 is the mass of the sample before drying and M2 is the mass of the sample after
drying.
Data taken from the post-tanned chromium samples were plotted to show the change in
weight relative to the starting weight, in conditions of differing relative humidity. The pre-
conditioned samples (or damp non-conditioned leather) were further cut according to mode
used and then loaded into the dynamic mechanical thermal analysis tester (DMTA) and
allowed to run for 35-40 minutes while the viscoelastic properties were recorded.
Dynamic mechanical thermal analysis
DMTA was run (in triplicate) on damp leather samples representing the four tannage/post
tannage types. The DMTA programme used was a declining, ramped, relative humidity
profile (85 to 45% RH, 10%/min), at an isothermic temperature (40°C or 60°C). A declining
INVESTIGATING THE CELL ROTARY CONDITIONING MECHANISM USING DYNAMIC MECHANICAL ANALYSIS.
K. B. FLOWERS*1, A. PERUZZI2, W. R. WISE1, AND A.D. COVINGTON1
9.
ramp rather than a static RH prevented case-hardening. Start and end wet moisture contents
were measured using BS EN ISO 4684:200551.
The DMTA equipment used in this research was a Tritec DMTA 2000 (Triton Technology).
The heating/cooling unit was a Grant Optima TX150 (Grant Instruments, Shepreth, UK). The
humidity chamber was a Lacerta humidity chamber (Lacerta Technology limited, Keyworth,
UK).
The DMTA was used in dual-cantilever (DC) bending mode (narrow disk orientation, free
length 15 mm): DC bending mode was used even though the sample modulus and thickness
were, at times, out of range of the preferred method. Dynamic displacement of sample during
runs was always set at 64 μm and scans were run at 1 Hz unless stated otherwise.
Software control of DMTA scans was managed using a Microsoft Excel® 2003 plugin from
which the data was exported. The storage modulus (E’) and damping ratio (tan δ) were the
main data values used in the characterisation of leathers.
Differential Scanning Calorimetry
The differential scanning calorimetry (DSC) of all upholstery leather types was performed on
a Mettler-Toledo DSC 822e (Mettler-Toledo, Leicester, UK) using an empty aluminium pan
as a reference. The DSC test was done to measure the static thermal properties. A flow of 70
mL/min of nitrogen gas was maintained over the sample in the furnace during the scan. Peak
area and onset/peak temperature data from integrations of the thermal profiles were
performed using the STARe v. 9.1 software (Mettler-Toledo, Leicester, UK). Samples
weights (3.0±0.5 mg) for DSC were fully hydrated and enclosed in a sealed pan. The heating
rate of each scan was 5°C/min.
DSC shrinkage temperatures were cross-checked using a shrinkage temperature apparatus
according to BS EN ISO 3380:2002 at a heating rate of 2°C/min52.
RESULTS/DISCUSSION
Leather raw materials (Gravimetric analysis)
Pre-conditioning of leathers to produce leathers of differing moisture content using
conditioning chambers and saturated salt solutions produced moisture profiles that were
similar to those reported by other authors30,50,53,54. Figure 2 shows that leathers conditioned at
98% RH give leathers with a moisture content (on a dry basis) of 68.1±4.3%; 76% gave
24.2±5.0% and 47% gave 13.4±2.4%.
INVESTIGATING THE CELL ROTARY CONDITIONING MECHANISM USING DYNAMIC MECHANICAL ANALYSIS.
K. B. FLOWERS*1, A. PERUZZI2, W. R. WISE1, AND A.D. COVINGTON1
10.
Figure 2. Moisture profiles of post tanned chromium leathers pre-conditioned at 98%, 76% and 45% relative
humidity in constant environment chambers. Drying was performed at 23°C.
The post-tanned chromium leathers that were pre-conditioned showed variable levels of
moisture content even though precautions were taken to prevent this.
Static thermal studies
The four leather types were measured on a DSC according to the method given above.
Results given below in Table II show that the leathers that did not receive post tannage had
onset temperatures (an indication of shrinkage temperature) that were within the expected
range for the type of tannage used.
TABLE II.
Differential scanning calorimetry data obtained from thermal scans of the four
types of leathers used in this study.
Leather type
Onset temperature (°C)
Chromium tannage only
104.95
GTA tannage only
75.16
Cr tanned and post tanned
93.89
GTA tanned and post tanned
78.24
The retannage/dyeing and fatliquoring operations of the chromium tanned leather seems to
lower its thermal stability. One of the likely explanations for this is the removal of some of
the sulfate by washing and chemical replacement from the chromium complexes.
INVESTIGATING THE CELL ROTARY CONDITIONING MECHANISM USING DYNAMIC MECHANICAL ANALYSIS.
K. B. FLOWERS*1, A. PERUZZI2, W. R. WISE1, AND A.D. COVINGTON1
11.
Dynamic thermal studies
Leathers were analysed using DMTA in DC bending mode. Acquiring good information
about what is taking place during drying is possible when using the DMTA in dual cantilever
bending mode. As the drying progresses the storage and loss modulus increase, see Figure 3.
The increase in moduli is not always proportional so a researcher can also see any changes in
the tan δ value.
Generally, researchers use the moduli values to ascertain whether the material is becoming
more viscoelastic or “stiffer”. In general, the leathers lost their flexibility and became stiffer.
The rate of viscoelasticity change differed according to drying method and it is these
variations that the research is highlighting.
Figure 3 and 4 show the DC bending mode at 40 and 60°C and it shows the effect that drying
temperature and drying humidity exert together on the drying profile. As the temperature is
raised, the storage modulus is increased, see Figure 3 and 4. Stiffer/drier leather is expected
in leather, as higher temperatures result in faster moisture removal from the interfibrillary
spaces and additionally provides more activation energy for fibre cohesion.
Figure 3. Four damp leather types dried at 40°C in a DMTA instrument and their storage modulus measured at 1
Hz showing variable change in modulus. The leathers were dried where the relative humidity began at 85% and
decreased to 45% at 10%/min. The starting moisture content for all leathers was 65% and did not go past 35% in
any of the leathers after 40 minutes.
INVESTIGATING THE CELL ROTARY CONDITIONING MECHANISM USING DYNAMIC MECHANICAL ANALYSIS.
K. B. FLOWERS*1, A. PERUZZI2, W. R. WISE1, AND A.D. COVINGTON1
12.
Figure 4 shows that the plasticising effect of water on the post tanned pieces is higher, due to
both the retanning chemicals having a higher hydrophilicity and a chemistry that allows
increased molecular volume and rotational freedom. The post tanned leather seems to release
its water rapidly in a manner different to non-post tanned material and this may be attributed
to the retanning and fatliquor content as suggested by Liu et al.14. There is not a large
difference between chromium and non-chromium tanned material that has been post tanned,
in terms of their drying profile at 60°C.
Figure 4. Four damp leather types dried at 60°C in a DMTA instrument and their storage modulus measured at 1
Hz showing variable change in modulus. The leathers were dried where the relative humidity began at 85% and
decreased to 45% at 10%/min. The starting moisture content for all leathers was 65% and the post tanned
leathers dried to below 10% moisture after 40 minutes.
Rapid increase in viscoelasticity is undesirable in leather manufacture as the resulting leather
has a higher E’ value (giving firmness to soft leather) and can often leave the leather fibres
brittle. It is also known from many sources that very rapid drying affects area yield1,5,33,37,41,55-
57. DMTA in DC bending mode does not give data that inform what happens to the area yield.
CONCLUSIONS
Analysis using DMTA drying of the four leathers has shown that storage modulus during
leather drying changes at rates governed by the drying parameters used.
INVESTIGATING THE CELL ROTARY CONDITIONING MECHANISM USING DYNAMIC MECHANICAL ANALYSIS.
K. B. FLOWERS*1, A. PERUZZI2, W. R. WISE1, AND A.D. COVINGTON1
13.
The research conducted did not corroborate findings, where Liu et al. suggest the tannage
itself changes the rate of drying, but indicates that leathers with different tannages end with
different stiffness values because they start with different viscoelasticity values8,9. However,
it has shown that post tanned leathers do differ in their rate of drying, but it seems the leather
tannage forms the basis for how the post tannage chemicals interact with the tanned leather
collagen, so ultimately influence the degree of plasticization and the viscoelasticity of the
resulting leather.
Covington in an updated theory on tannage suggests that the role of water in the thermal
stability is crucial. An additional effect of tannage on the water content of the collagen is its
combined influence that it (and other plasticizers) have on the storage modulus. This research
found that the role of post tannage has a greater effect than the tanning chemicals in drying in
terms of storage modulus58.
It has been seen that the two (possibly even all three) phases of drying should be seen as
separate considerations. First-phase drying temperature is governed by a modification of
Regnault’s formula. Second-phase drying is dominated by temperature and humidity transfer.
Third-phase drying is dominated by collagen desorption mechanics.
The viscoelasticity that can be measured by DMTA allows insight directly into what is taking
place in terms of leather elasticity and set. More research needs to be performed on exactly
how the post tannage and the combined effects of drying temperature/humidity affects the
drying rates, physical properties as well as the area yield.
ACKNOWLEDGEMENT
ICLT would like to express its gratitude to Fratelli Carlessi, and in particular A. Galiotto and
A. Peruzzi, for their support/assistance in allowing the University of Northampton access to
their CRC machine and in supplying information and expertise.
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INVESTIGATING THE CELL ROTARY CONDITIONING MECHANISM USING DYNAMIC MECHANICAL ANALYSIS.
K. B. FLOWERS*1, A. PERUZZI2, W. R. WISE1, AND A.D. COVINGTON1
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