Scholarly article on topic 'Nano-emulsion based on acrylic acid ester co-polymer derivatives as an efficient pre-tanning agent for buffalo hide'

Nano-emulsion based on acrylic acid ester co-polymer derivatives as an efficient pre-tanning agent for buffalo hide Academic research paper on "Chemical sciences"

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Arabian Journal of Chemistry
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{"Acrylic acid ester copolymers" / Nanoemulsion / "Pre-tanning agent" / "Depickled hide" / "Chrome tan" / "Chromium uptake"}

Abstract of research paper on Chemical sciences, author of scientific article — Farouk Abd El-Monem, Ahmed I. Hussain, EL-Shahat H.A. Nashy, Hamada Abd El-Wahhab, Abd El-Rahman M. Naser

Abstract Acrylic copolymer nanoemulsions were prepared based on methyl methacrylate (MMA) and butyl acrylate (BA). The prepared acrylic copolymer emulsions were characterized using solid content, rheological properties, molecular weight, MFFT and TEM. The prepared polymers were used as pre-tanning of the depickled hide to enhance the physico-mechanical properties of tanned leather. The key parameters which affect exhaustion and fixation of chrome tan as well as shrinkage temperature of the tanned leather were studied and evaluated using SEM, shrinkage temperature and the mechanical properties of the pre-tanned leather. The results showed that, the prepared polymers A & C are the best polymers in improving the physical properties of the treated leather. Furthermore, the shrinkage temperature and the mechanical properties of the tanned leather were improved. In addition, a significant enhancement in the texture of the leather treated by the polymers was noticed as proved by scanning electron microscopy (SEM).

Academic research paper on topic "Nano-emulsion based on acrylic acid ester co-polymer derivatives as an efficient pre-tanning agent for buffalo hide"

Arabian Journal of Chemistry (2014) xxx, xxx-xxx

King Saud University Arabian Journal of Chemistry

www.ksu.edu.sa www.sciencedirect.com

REVIEW

Nano-emulsion based on acrylic acid ester co-polymer derivatives as an efficient pre-tanning agent for buffalo hide

Farouk Abd El-Monem c *, Ahmed I. Hussain a, EL-Shahat H.A. Nashy b, Hamada Abd El-Wahhab c, Abd El-Rahman M. Naser c

a Polymers and Pigments Dept., National Research Centre, Dokki, Cairo, Egypt

b Chemistry of Tanning Materials and Leather Technology Dept., National Research Centre, Dokki, Cairo, Egypt c Chemistry Department, Faculty of Science, Alazhar University, Egypt

Received 1 March 2014; accepted 30 May 2014

KEYWORDS

Acrylic acid ester copolymers; Nanoemulsion; Pre-tanning agent; Depickled hide; Chrome tan; Chromium uptake

Abstract Acrylic copolymer nanoemulsions were prepared based on methyl methacrylate (MMA) and butyl acrylate (BA). The prepared acrylic copolymer emulsions were characterized using solid content, rheological properties, molecular weight, MFFT and TEM. The prepared polymers were used as pre-tanning of the depickled hide to enhance the physico-mechanical properties of tanned leather. The key parameters which affect exhaustion and fixation of chrome tan as well as shrinkage temperature of the tanned leather were studied and evaluated using SEM, shrinkage temperature and the mechanical properties of the pre-tanned leather. The results showed that, the prepared polymers A & C are the best polymers in improving the physical properties of the treated leather. Furthermore, the shrinkage temperature and the mechanical properties of the tanned leather were improved. In addition, a significant enhancement in the texture of the leather treated by the polymers was noticed as proved by scanning electron microscopy (SEM).

© 2014 King Saud University. Production and hosting by Elsevier B.V. All rights reserved.

Contents

1. Introduction .

2. Experimental.

* Corresponding author.

E-mail address: farouk_chem_ekhmu@yahoo.com(F.A. El-Monem). Peer review under responsibility of King Saud University.

http://dx.doi.org/10.1016/j.arabjc.2014.05.024

1878-5352 © 2014 King Saud University. Production and hosting by Elsevier B.V. All rights reserved.

2.1. Materials......................................................................................................................................................00

2.2. Experimental technique..................................................................................................................................00

2.2.1. Emulsion polymerization..........................................................................................................................00

2.2.2. Preparation of leather..............................................................................................................................00

2.3. Testing and analysis......................................................................................................................................00

2.3.1. Transmission electron microscopy (TEM) (Groves, 1978)............................................................................00

2.3.2. Scanning electron microscope examination (Nashy et al., 2012)..................................................................00

2.3.3. Mechanical properties..............................................................................................................................00

2.3.4. Thermal properties (Nashy et al., 2012)....................................................................................................00

2.3.5. Shrinkage temperature (Nashy et al., 2012)................................................................................................00

3. Results and discussion ..........................................................................................................................................00

3.1. Characteristics of the prepared emulsion copolymers of (MMA-co-BA) as pre-tanning agent................................00

3.1.1. Effect of butyl acrylate on viscosity of the prepared polymer......................................................................00

3.1.2. Molecular weight and Molecular weight distribution..................................................................................00

3.2. Transmission electron microscopy (TEM) of the prepared polymers ..................................................................00

3.3. Emulsion polymers of MMA-co-BA as pre-tanning agent..................................................................................00

3.4. Characteristics of the pre-tanned leather ..........................................................................................................00

3.4.1. Mechanical properties..............................................................................................................................00

3.4.2. Tensile strength ......................................................................................................................................00

3.4.3. Elongation at break ................................................................................................................................00

3.4.4. Thermal study (TGA)..............................................................................................................................00

3.4.5. Scanning electron microscope (SEM) ........................................................................................................00

3.4.6. Shrinkage temperature............................................................................................................................00

4. Conclusions ........................................................................................................................................................00

References ..............................................................................................................................................................00

1. Introduction

Chemically, polymers are long-chain molecules of very high molecular weight, often measured in hundreds of thousands. The trade literature sometime refers to polymers as resins (Sperling, 2006). The emulsion polymerization is carried out in liquid medium, which is almost always aqueous and produces milky fluid called latex (Yildirim Erbil, 2000).

Acrylic and methacrylic ester monomers have a combined worldwide production of near about 2 million tons/year (Lochmann and Lim, 1973; Lochmann et al., 1974) .The polymer products derived from these monomers, and n-butyl acry-late and methyl methacrylate are the most common monomers utilized. Poly (w-butyl acrylate) (PBA) (Tg = -55 0C) is soft, tacky, and rubbery while poly (methyl methacrylate) (PMMA) (amorphous, Tg = 105 0Q is hard, tough, and rigid.

Generally, methacrylates have higher tensile strength and lower elongation than acrylates. This difference in properties is attributed to the substitution of the a-hydrogen in acrylates by a methyl group in methacrylates, which results in restriction of motion and rotation of the polymer backbone (Lochmann and Lim, 1973; Lochmann et al., 1974; Mokhtari et al., 2013a,b).

The copolymerization of acrylates and methacrylates increasing the range of polymer properties available (Lochmann and Lim, 1973; Lochmann et al., 1974). The hardness or flexibility of the copolymer is a function of the composition of the monomer, and necessary adjustments are readily achieved by varying the (co)monomer composition. In general, acrylic ester copolymer nanoemulsion is of immense importance for industrial applications (Mokhtari and Pourabdollah,

2012a,b, 2013). Therefore, this work was devoted to explore their application for further use in the leather industry as pre-tanning agents (modifying agent) in leather industry processes.

Over several decades leather technology literature has been dominated by ways to reduce the environmental impact of leather production and techniques. Hides are obvious natural proteins which are easily attacked by organisms and prone to putrefaction.

Tanning operation is one of the most important steps in tanning industry, in which protein of raw hide is transformed into a stable fiber structure (leather). There are many types of tanning agents; the most applied is the chrome tan (Hauber and Germann, 1999). Chrome tannage has proven to be the effective method of tanning and is done in tanneries worldwide. It is used for the production of the great majority of various types of leathers such as upper garments and other light leathers (Wachsmann, 2001). Chrome tan gained the leather better characters other than tanning agents such as high thermal stability, light weight and high strength properties (Bieniewics, 1983; Srearam et al., 2003). Usually, it accounts more than 80% of the tanning industry consumption worldwide (Hauber and Germann, 1999).

Despite the many advantages offered by chrome tanning, there is a worldwide interest in containing the chrome waste. Therefore, there is a growing need for eco-benign tanning systems owing to stringent environmental regulations. Therefore, this work emphasizes the principle of prevention is better than treatment based on the preparation of acrylic copolymer nanoemulsions as an efficient pre-tanning agent for chrome tan.

2. Experimental

2.1. Materials

- Butyl acrylate (BA) and Methyl Methacrylate (MMA) were supplied by Sigma Aldrich and distilled with reduced pressure before use and stored at —20 0C.

- Potassium persulfate (KPS), nonyl phenyl ethoxylated (NP30), Cetyl alcohol (CA), sodium bicarbonate, ammonia water, acrylic acid (AA), acrylamide (AM) and Basic Chromium (III) Sulfate were supplied from Sigma chemicals. Distilled water was used. All chemicals were fine chemicals.

- Egyptian buffalo hides.

2.2. Experimental technique

2.2.1. Emulsion polymerization

2.2.1.1. Pre-emulsion. Distilled water, ionic surfactant and monomers were added in the flask equipped with a high speed homogenizer (ultra turax homogenizer) for 30 min (in three time portions). The acid monomer (AA) is added during continuous homogenization.

2.2.1.2. Emulsion polymerization. Emulsion polymerization of methyl methacrylate and/or butyl acrylate, was carried out in a 500 mL three-necked round bottomed flask equipped with a stirrer, a gas inlet system and a reflux condenser immersed in a water bath. The oxygen was removed by purging the flask by nitrogen.

30% of used distilled water was introduced into the glass reactor with non-ionic surfactant. The mixture was stirred under a blanket of nitrogen at 80 0C followed by the addition of sodium bicarbonate to adjust the pH of the reaction medium.

The prepared pre-emulsion was charged into the reactor. Then, the initiator system was gradually dropped. The reaction was allowed to proceed for 4 h under continuous stirring at 80 rpm with the addition of calculated amount of initiator. At the end ofthe pre-emulsion addition, the temperature was raised from 80 to 85 0C for 1 h to complete the polymerization reaction. The prepared emulsion was cooled to 40 0C and the pH adjusted using aqueous solution of ammonia to pH 8.

2.2.1.3. Molecular weight determination (Malihi et al., 1984). In 2mL of THF solvent 0.01 gm was dissolved, and filtrated by siring filter 0.45 micro then the sample but in GPC device (Agilent 1100 series, Germany, Detector: Refractive Index). Using three columns of pore type (100, 104, 105 A) on series, length 7.5 x 300 mm (Mw1000, 4,000,000) of THF solvent (polystyrene standard) Plgel particle size (5 im).

2.2.2. Preparation of leather

The raw hide selected for the present investigation was commercially Egyptian buffalo hide. The samples were worked up in the beam house operation as usual. Slow additions of the reagents were done and all percentages of reagents were calculated on the dry weight of pickled hide.

2.2.2.1. Pre-tanning process. Pickled hides in each method were adjusted at pH = 2.5, then, 10% NaCl was added for 30 min

as de pickled stage. The de-pickle pelt samples were modified with the prepared polymers as pre-tanning agents before being tanned with basic chromium sulfate (BCS, chromosal B 32.51% basicity). This means that the pre-tanning process was carried out using different doses (2%, 4% and 6%) of different types of polymers (A, B, C, D, E, and F). Then tanning process was carried out using 5% BCS for 2 h followed by 5% of BCS for another 2 h.

2.3. Testing and analysis

2.3.1. Transmission electron microscopy (TEM) (Groves, 1978)

The morphology of the polymer particles was examined using TEM. For the present work, the use of cryo-TEM was required because of the low glass transition temperature of the prepared polymer. To perform cryo-TEM analysis, the latex was diluted with distilled water. A drop of the diluted latex was placed on a carbon-coated grid and dried in a dissector. Then, 1-2 drops of a 0.8 wt% aqueous solution of phosphotungstic acid (PTA) were used to stain the particles.

2.3.2. Scanning electron microscope examination (Nashy et al., 2012)

Specimens for this study were cut from the samples. Specimen size was 10 mm diameter and it was circular in shape. These samples were subjected to sputter coating (Edwards's model S 140A) of gold ions to have a conducting medium. Sputter coated samples were scanned with JEOL Model JSM-T20 SEM.

2.3.3. Mechanical properties

The tensile strength and elongation at break properties of the dumbbell samples were measured according to ASTM D 412, using Ziwick tensile testing machine, with crosshead speed of 200 mm/min, and the average value of mechanical properties was calculated using at least five samples.

2.3.4. Thermal properties (Nashy et al., 2012)

The thermo gravimetric analysis (TGA) measurements for the obtained grafted samples were carried out at temperature range starting from 50 0C to 700 0C under nitrogen atmosphere with a heating rate of 10 0C/min using Shimadzu TGA-50, Japan.

2.3.5. Shrinkage temperature (Nashy et al., 2012)

A significant shrinkage is observed when it is exposed to a heating medium. The rise in shrinkage temperature of the tanned hide indicated the good effect of tanning agent. It was measured according to the conventional method and Egyptian Specification.

3. Results and discussion

This research aims to use nanoemulsion copolymer of poly (methyl methacrylate-co-butyl acrylate) as pre-tanning agent for buffalo hide to improve physical and mechanical properties of the tanned buffalo leather as well as to reduce the environmental impact of chrome tan.

The emulsion copolymerization of poly (methyl methacrylate-co-butyl acrylate) was carried out at different

Table 1 Recipe for different ratios of methyl methacrylate/butyl acrylate emulsion copolymer containing acrylic acid and acrylamide.

Component A B C D E F

Methyl Methacrylate (gm) 90 75 60 90 75 60

Butyl acrylate (gm) 60 75 90 60 75 90

Acrylic acid (gm) 6 6 6 3 3 3

Acrylamide (gm) 0 0 0 3 3 3

H2O (gm) 150 150 150 150 150 150

The above recipe contains pot. Persulfate as free radical initiator (0.f >), Cetyl alcohol (2.4), and sodium lauryl ether sulfate (6.6 ). All chemicals

weighted in gms.

Table 2 Characteristics of the prepared copolymer emulsion.

Properties Standard Value

ASTM A B C D E F

pH 8.3 8.2 8.3 8.1 8.0 8.1

Solid Content (%) D2369 50.1 49.6 50 50 49.5 50.2

Conversion (%), Piirma, 1982 100 99.4 100 99.8 99.7 100

Drying time (sec) at 23 °C, Nashy et al., 2012 70 95 115 75 100 120

Particle size (nm) TEM 85 71 70 170 130 100

Brookfield Viscosity RVT #50 rpm, (cps) D2196 - 99 55,000 73,000 90,000 22,000 27,000 30,000

100000

90000 80000 70000 60000 50000 40000 30000 20000 10000 0

C Polymer group D

Figure 1 Butyl acrylate/methyl methacrylate (%).

concentration ratios (MMA or BA) respectively in the presence of acrylic acid and/or acrylamide as thickening agents, potassium per sulfate as initiator and Cetyl alcohol and SLES as surfactants, Table 1.

3.1. Characteristics of the prepared emulsion copolymers of (MMA-co-BA) as pre-tanning agent

The prepared polymers were investigated by testing: solid content, M.wt, coagulum, viscosity, drying time, MFFT, TEM and SEM. The mechanical properties of the prepared leather samples were also examined to study the characteristics of the polymer. The physical, chemical as well as mechanical properties of the prepared polymer emulsions were examined according to the international standard as shown in Table 2.

3.1.1. Effect of butyl acrylate on viscosity of the prepared polymer

The data obtained from Table 2 were planned in Fig. 1 showing the relation between viscosity of the prepared samples and changing hydrophobic butyl acrylate concentrations with acrylic acid. It is obvious that the viscosity of copolymers increased as the concentration of butyl acrylate increased.

Figure 2 TEM of prepared emulsion copolymer (D).

3.1.2. Molecular weight and Molecular weight distribution It is clear that the copolymer (D) (M.wt. = 3.1726e5 g/mol, Mn = 7.0307e4 g/mol) has a higher molecular weight and molecular weight distribution than copolymer (C) (M.wt. = 2.7435e5 g/mol, Mn = 6.9769e4 g/mol).

Figure 3 TEM of prepared emulsion copolymer (F).

3.2. Transmission electron microscopy (TEM) of the prepared polymers

The morphology of the particles was examined using TEM. Figs. 2 and 3 show the TEM of the prepared emulsion lattices. It is clear that, the particle size of the prepared lattices ranged about 170 nm for polymer (D) which prepared with acrylic acid as thickening agent and high content of methyl methacrylate, while the particle size of polymer (F) ranged about 100 nm which prepared from acrylic acid and acrylamide as

thickening agent and high content of butyl acrylate. It has also been reported that the hydrophobic/hydrophilic character of the monomer(s) used in emulsion polymerization has a decisive influence on particle morphology: according to the data obtained by Snuparek et al. (2005) macromolecules with an increase in hydrophilicity facilitate carboxyl ionization, resulting in higher particle swelling (increase in viscosity) and particles with high contents of AA and/or acrylamide being completely solubilized. Usually, carboxylic acids are added to improve the mechanical, freeze-thaw, and pigment mixing stability of the lattices.

Carboxylic acid monomers are often completely soluble in water; however, they will still distribute to vary extents into the organic phase depending on their relative hydrophilicity.

3.3. Emulsion polymers of MMA-co-BA as pre-tanning agent

Pre-tanning process was carried out with two groups of polymers using different doses of 2%, 4%, and 6%, respectively. Pickled hide was treated with sodium format and sodium chloride to adjust the pH through the all its thickness as well as to eliminate out the acid and salts. This process (depickling) is a very important process to prevent the acid or salt hydrolysis of protein fibers. The depickled pelt samples were modified with the prepared polymers as pre-tanning agents before being tanned with basic chromium sulfate (BCS).

Polymer concentration (%)

Figure 4 Tensile strength of pre-tanned buffalo hide (transverse).

Polymer concentration (%)

Figure 5 Tensile strength of pre-tanned buffalo hide (longitudinal).

g 200 -fi

« 180 ■s 160

Ц 140 _o

S 120 100

Polymer Concentration (%)

Figure 6 Elongation at break of pre-tanned Buffalo hide (transverse).

Figure 7 Elongation at break of pre-tanned buffalo hide (longitudinal).

The pre-tanning process of buffalo hides was done as follows:

(1) Treatment of pickled hide with 10% NaCl for 30 min as depickled agent.

(2) The depickled pelt was pre-tanned by 2%, 4% and 6% doses of different types of polymers.

(3) The full tanning process by (BCS) was carried out through adding 5% BCS for 2h followed by 5% BCS for another 2 h. Tanning allows stabilization of the collagen fiber through a cross-linking action with active sites of proteins. The tanned hides and skins are tradable intermediate products (wet-blue).

1mm 1 45x

Figure 8a SEM of grain surface of chrome tanned leather (X45).

3.4. Characteristics of the pre-tanned leather 3.4.1. Mechanical properties

Mechanical properties have generally been given the greatest consideration in the evaluation of leather. The mechanical characters include the measurement of the tensile strength and elongation at break. These characters were carried out according to the Egyptian standard method (ES-123) and official method. An average value of at least five tests was taken for each item. In general Figs. 6-9 showed an improvement in the mechanical properties of the treated leather by the prepared polymers than untreated leather. This may be due to

1mm 1 45x

Figure 8b SEM of the cross-section of chrome tanned leather (X80).

Figure 9b SEM of the cross-section of polymer (C) tanned leather (X80).

the good adhesion effect of the polymer on hide fiber of the leather and also due to the filling action on grain layer.

3.4.2. Tensile strength

Figs. 4 and 5 show tensile strength of the tanned leather samples at both transverse (Fig. 4) and longitudinal directions (Fig. 5) by different types of polymers.

Fig. 4 shows tensile strength of the tanned leather samples at transverse direction by different types of polymers with doses 2%, 4% and 6% respectively, it is obvious from Fig. 4 that; the polymer (A) achieved good tensile strength at 4% concentration compared with the other polymers.

Fig. 5 shows that; the polymer (A) achieved good tensile strength compared with the other polymers. It can be

§> 40

J 20 0

Cr 10% F 4%&10% Cr C 4% 10% Cr A4%10%Cr D4%10%Cr Copolymer (%)

Figure 11 Shrinkage Temp. for copolymers as pretanning agent.

Table 3 TGA of prepared samples (chrome tanned and pre-tanned hide with copolymers and tanned by chrome).

Temperature Weight loss (%)

at (°C) Chrome pre- Tanned leather by Tanned leather by Tanned leather by Tanned leather by

tanned leather polymer C polymer F polymer A polymer D

75 15.188 10.978 11.581 14.583 11.851

300 33.471 26.256 26.013 28.754 24.820

500 62.156 74.55 69.536 67.126 63.899

720 90.056 93.602 84.004 82.836 78.995

Table 4 Shrinkage temperature for pre-tanning leather by polymers.

Pre-tanning agent Cr 10% F 4% & 10% Cr C 4% & 10% Cr A 4% & 10% Cr D 4% & 10% Cr

Shrinkage 87 70 90 93 60

concluded from Figs. 4 and 5 that the polymer (A) is the best one in its effect on tensile strength at both longitudinal and transverse directions of 4% concentration.

3.4.3. Elongation at break

Figs. 6 and 7 show elongation at break of the tanned leather samples at both transverse (Fig. 6) and longitudinal directions (Fig. 7) by different types of polymers with doses 2%, 4% and 6% respectively.

Fig. 6 shows that; the polymer (C) achieved good elongation at break, compared with the other polymers.

Fig. 7 is obvious that; the polymer (F) achieved good elongation at break, compared with the other polymers.

In general it was noticed that the polymer (A) showed improved tensile strength compared with the other polymers. However, the elongation at break was improved for polymer (C) in the transverse section while elongation at break was improved in polymer (F) in the longitudinal section. The improvement of elongation by polymers (C and F) can be attributed to the lubricating effect of polymer. The lubrication effect reversed to these two polymers (C and F) has a higher ratio of butyl acrylate which has elastic properties than methyl methacrylate and also has smaller particle size compared with the other polymers.

3.4.4. Thermal study (TGA)

The TGA and Dr-TGA curves are shown in Table 3 and the TGA analysis shows that, the decomposition temperature of the polymer tanned leather is of higher degrees than those of the chrome tanned leather. Thus, the incorporation of the polymer into leather increases the thermal stability of the polymer leather over that of the chrome tanned leather. This improvement in thermal stability can be attributed to the formation of polymer - collagen composite, which can be explained by brought about multiple weak hydrogen bonding between the numerous carbonyl groups (C=O) of the polymers and the countless hydrogen atoms of (NH) peptide groups, which support of the junction between the grain and corium. These results indicate that polymers fill up the empty parts of leather and lubricate the leather fibers.

3.4.5. Scanning electron microscope (SEM)

The morphological study of the chrome tanned leather was carried out in comparison with tanned leather by copolymers (A, B, C, D, E and F). SEM can be used to assess the penetration of the polymer through the leather and into the hierarchy of the structure and is thus a useful technique for evaluating the effects of various treatments on the skin. SEM of the grain surface (X45) and the cross-section of the (X80) of the skin with and without polymers was carried out to show the effect of the prepared polymers on the grain and fiber bundles as pre-tanning agents (Figs. 8-10a and b). The SEM of the cross section of the leather fibers tanned by the polymers showed a significant lubrication of fiber bundles (Figs. 8-10b) and surface grain is fine (Figs. 8-10a). It was observed that the SEM of

the samples pre-tanned by polymers (C&A) has a smooth fiber, firmness grain and modified handle, which are good evidence for the penetration and lubrication of copolymers onto the leather fibers and grain surface. The pre-treated chrome tanned leather by polymers gives better grain smoothness, soft fibers, filling and modified handle. The filling of the grain layer improves buff ability for uses as corrected grain leather.

3.4.6. Shrinkage temperature

Fig. 11 and table 4 represent shrinkage temperature of the tanned leather samples by chrome and by different types of prepared polymers at the same dose (4%). It is obvious that; the polymer (A) achieved good shrinkage, compared with other samples treated with polymers (F, C, D and Cr).

Shrinkage temperature was measured according to the conventional method and Egyptian Specification. The treated leather with polymers (A, D, C and F) as well as tanned leather were subjected to shrinkage testing. A significant shrinkage is noticed when it is exposed to a heating medium. The rise in shrinkage temperature of the pre-tanned hide with polymers (A and C) indicated the good effect of tanning agent.

4. Conclusions

The obtained results of this work indicated that, the characters of the pre-tanned leather are improved in the following respects:

- Emulsion polymerization is a flexible process by which a wide range of practical materials can be made, and in each case, the process is tailored to optimize the performance properties of the final product.

- The visual properties of the treated leather through fullness and tight grain were modified due to the filling action of nano-particle copolymer.

- The best tensile strength was obtained with polymer (A) when applied as pre-tanning agent due to a high content of MMA.

- The polymers (C and F) improve the elongation at break when applied as pre-tanning agent depending upon its lubrication.

- Replacing chrome by 4% polymer (A or C) for pre-tanning process increased leather shrinkage temperature.

- Enhancement the thermal stability of the treated leather.

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