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Ramazanov Bahrom Gafurovich, Bukhara engineering-technological institute Kadirov Tulkin Jumaevich, Tashkent institute of textile and light industry E-mail: b.ramazanov75@mail.ru
INVESTIGATION OF STRUCTURAL FORMATION OF AMINOALDEHYDE OLIGOMERS IN THE INNER SURFACE OF LEATHER
Abstract: The article deals with the research of the microstructure of the leather, various fillers and the importance of the filling process are given to improve the complex parameters of the leather.
Keywords: leather microstructure, amino aldehyde oligomers, filling, complex quality indicators, control and filled leather samples.
In order to improve many physicochemical and mechanical indicators of materials, especially porous solids, the process of filling them is carried out. To do this, it is first expedient to investigate the microstructure of the material under study. To solve the problem associated with a decrease in leather porosity, we thoroughly studied its microstructure, after which it was decided to fill the leather materials.
The inner part of the natural leather is a system consisting of capillaries, micro- and macro-structural aggregates. It is known that treating the leather with hydrophilic polymers contributes to a decrease in the porosity of the leather [1]. Proceeding from this, the study of the structure formation in
Table 1.- Physicomechanical parameters of initial and amino aldehyde-loaded leather
the inner surface of the leather of amino aldehyde oligomers is of great importance.
Table 1 lists numerous physico-mechanical properties of the leathers established for the initial and filled with amino aldehyde oligomers.
As follows from the data in the table, the porosity of the samples as a result of filling decreases sharply. Naturally, the effect depends on the type of filler [2; 3] Simultaneously, an increase in tensile strength of the specimens was observed. Thus, when using modified amino-aldehyde oligomers, the porosity is much less.
Physical and mechanical properties control (unfilled) KFO KFCrAO KFMAO KFCrAMAO
The content of unreacting oligomer,%* - 0.5 0.5 0.6 0.6
Plyves,% - 4.8 5.0 5.7 6.2
Total pore volume, cm3/g 0.896 0.684 0.726 0.579 0.465
True specific gravity, g/cm3 1.20 1.32 1.33 1.35 1.36
Porosity,% 43.4 32.4 30.2 26.7 24.5
Water vapor permeability,% 58.6 46.9 45.7 42.6 41.9
Sample thickness, mm 1.7 2.1 2.2 2.4 2.5
Rigidity,% 24.8 28.5 29.6 32.4 34.1
Tensile strength, MPa 2.32 2.52 2.54 2.65 2.73
Elongation at break,% 83.5 75.3 71.4 68.9 64.2
Elongation at a voltage of 9,8 MPa,% 18.0 19.4 20.2 21.8 23.2
Residual elongation,% 34.0 29.6 28.1 26.5 24.5
Conditional modulus of elasticity, MPa 56.4 48.7 50.2 52.8 54.0
* The content of the polymerized and unreacted oligomer was
Extremely urgent is the elucidation of complex indicators for a more complete assessment of the chemical and physico-mechanical properties of the leather, which have a dominant effect on the process of filling with polymers. To this end, various methods of assessing the quality of raw materials, semi-finished products and end products are
determined on a Zaichenko device
widely used. However, the known methods are very durable for filling, time-consuming and not always reliable the data received. From the point of view of the influence of the process of filling leathers with amino-aldehyde oligomers, it is very important to use a complex quality indicator (CQI) for the most objective assessment of the consumer, chemical
and physical-mechanical properties of the leather. The CQI the basic properties of the leather. Next, based on the selec-was defined as the area of a polygon composed of twelve tive indicators that make up the CQI, polygons were built basic indicators, determined experimentally, characterizing (Figure 1).
Figure 1. Complex quality indicators of the test control (unfilled) and experimental leather variants with amino-aldehyde oligomers
Note: the order of the values, in order, the marked figures in the figures: I - Gain,%; II - Water vapor permeability,%; III - Total pore volume, cm3/g; IV - Porosity, %; V - Sample thickness, mm; VI - Hardness,%; VII - Conditional modulus of elasticity, MPa; VIII -Ultimate tensile strength, MPa; IX - Elongation at a voltage of 9,8 MPa, %o; X - Residual elongation,%; XI - Specific gravity, (true) g/
cm3 and XII- Elongation at break, %
Conditionally denoting the sides of the triangles ax, #2, a . au, the angle a and the area of the triangles sx, S2, S3, ... Sj2 calculate the common surface as the sum of the surface of the individual triangles
S = Si + s2 + S3... + S12 (1)
The area of the triangle was calculated by the formula:
a • b • Sina
ax • a2 • stna
s —
a, • a • sina
+... +
+ a9 • a10 • sina + an • an • sina
(3)
S =
2
(2)
In formula (2), for all triangles, the angle a is 30 Therefore, the area of this figure can be calculated by the formula:
2 2 The results of calculating the areas of the triangles that make up the CQI of the experiment are shown in (Table 20).
From the data of (Table 2) it follows that relatively high chemical and physicomechanical properties are characterized by leather filled with KFCrAMAO. This can be easily explained, since the area of its polygon has the highest value of the CQI. The control and CQI of sample I have a relatively
low value (614.57 and 747.51 versus 883.14). Thus, the use of CQI s has made it possible to determine complex quality indicators of unfulfilled and leather-filled amino aldehyde oligomers. It should be noted that this method also allows more objective evaluation of the operational properties of finished products. From Table. 1 it can be seen that with the change in the compositions of amino aldehyde oligomers in the semi-finished products of the leather, the porosity and, to some extent, the leather's permeability are reduced. Reducing porosity (KFO - KFCrAO - KFMAO - KFCrAMAO) is undoubtedly due to the filling of empty spaces inside the leather
Table 2.- The areas of triangles that
with amino aldehyde oligomeric particles. Confirmation of this conclusion is obtained by us electron microscopic images of microstructures of samples, which are presented in (Fig. 2).
The data of physicomechanical analysis showed that with the change in the composition of oligomers in the semifinished product, the thickness (by 32.0%) and the tensile strength (15.0%) increase, and the porosity (43.5%) and the residual elongation (27.9%), in the case of modified amino-aldehyde oligomers, decreases. The index ofvapor permeability is the same, although it decreases, but not very much. This indicates that the micropores are preserved to a certain extent.
make up the CQI of the experiment
№ Indicators Control. KFO* KFCrAO KFMAO KFCrAMAO
A[1] Plyves 0 56.28 57.13 60.70 64.94
A[2] Water vapor permeability 13.23 8.02 8.29 6.17 4.87
A[3] Total pore volume 9.72 5.54 5.48 3.86 2.85
A[4] Porosity 18.45 17.01 16.61 16.02 15.32
A[5] Sample Thickness 10.54 14.96 16.28 19.44 21.32
A[6] Rigidity 14.26 17.96 18.80 21.47 23.28
A[7] Conditional modulus of elasticity 349.68 346.98 371.48 427.68 460.35
A[8] Ultimate tensile strength 10.44 12.22 12.83 14.44 15.84
A[9] Elongation at a voltage of 9,8 MPa 153.00 143.56 141.90 144.42 143.71
A[10] Residual elongation 10.20 9.77 9.34 8.94 8.33
A[11] Specific gravity 25.05 24.85 23.74 23.25 22.82
A[12] Elongation at rupture 0 90.36 89.25 98.18 99.51
Area of triangles Sj = 614.57 s2 = 747.51 s3 =771.13 s = 844.57 4 s5 = 883.14
*(I variant - Karbamid-Formaldehyde - MFO and II variant - Karbamid-Formaldehyde-Croton aldehyde - KFCrAO) have been obtained in the I and II variants, and in III and IV variants (III variant - Karbamid-Formaldehyde-Methacrylic acid-MFMAO and IV- Karbamid-Formaldehyde-Croton aldehyde Methacrylic acid - KFKrAMAO)
Taking into account the above, indirect coverage of structural elements of the leather by a layer of amino aldehyde oligomer can be indirectly assessed. In the case of an increase in the specific gravity of the samples, a decrease in their porosity and the preservation of the vapor permeability can be explained by the process of structure formation, i.e. the emergence of larger new structural aggregates.
This assumption is clearly illustrated by micrographs of sections of experimental and control leather samples. In Fig. 2(a, b) shows electron micrographs of sections of control and amine-aldehyde oligomer samples of leather prototypes.
To put it more accurately, it should be noted that in the process of filling natural leathers with KFO, KFCrAO, KFMAO and KFCrAMAO, distribution of amino aldehyde oligomers will take place on the surfaces of fibrillar aggregates in the leather microstructure (Fig. 2b).
In this case, to a certain extent, the separation of elements of structures of supramolecular collagen parts of fibers occurs.
This is largely due to surface activity, in comparison with organic salts, and involved in the modification of methacrylic acid molecules.
Investigation of the distribution of amine-aldehyde oligomer particles in the leather structure using the electron microscopy method has shown that in the case of KFCrAO and KFCrAMAO, its intense deposition is observed both in fibrils and in the interstructural space as separate disordered particles and clusters.
They certainly have different shapes and sizes. The particles of KFOs and KFCRAs have a different distribution pattern in the structure (Fig. 2). In the latter case, the absorption of oligomer particles and their fixation occurs only on the surfaces of the fibrils, and in the zones of their closure. Differences in the nature of deposition of amino aldehyde oligomers in the microstructure of collagen can be explained by the unequal degree of activity and the features of their chemical properties. The dispersed phase of KFMAO and
KFCrAMAO, apparently, has a better reactivity. Therefore, it is more evenly distributed in the structure of the leather compared to KFO and KFCrAOs.
It can be concluded that in the process of filling the leather with KFOs, KFCrAO, KFMAO and KFCrAMAO, their de-
control (unfilled)
position occurs on the surfaces of supramolecular collagen formations. At the same time, it should be pointed out that amino aldehyde oligomers are distributed uniformly on the surface of fibrils in the cases of KFMA and KFCrAMAO discretely under KFO and KFCrAO. This is due to their chemical nature.
II
III
IV
Figure 2. Electronic microphotographs of control structures - unfilled and prototype leathers filled with amino aldehyde oligomers: a - the front surface (x 100); b-section of the middle layer (x 5000). 1 cm 20 mkm
Thus, in the process of filling with amino-aldehyde oligomers predominantly with KFKrAMAO, the porosity decreases. The specific weight of the prototypes, in comparison with the control unfilled and the first prototypes, is significantly increased. This is explained by filling the pores. Obviously, this is due to the structuring effect of KFKrAMAO.
So, the structural studies carried out made it possible to establish and explain the effects that occur when the leather is filled with amino aldehyde oligomers. Because of solutions of aminoaldehyd oligomers are true and represent a relatively high dispersion, due to which they are able to penetrate deeply
into the microstructure of the leather and interact with the functionally active groups of amino acids.
Laying on the surfaces of fibrillar aggregates of collagen, aminoaldehyde oligomers block the active groups of amino acids of the protein, which is better structured. As a result of this the physicochemical and mechanical properties of the leather samples are improved. Simultaneously, the crosslinked oligomer introduced into the dermis of the leather wedges the collagen parts, which is the reason for the decrease in porosity, the increase in thickness and the specific weight of the semifinished leather.
I
References:
1. Juraev A. M., Akhmedov V. N., Toshev A. Yu., Kadirov T. Zh., Ramazanov B. G., Khudanov U. O. Investigation of the effect of water-soluble polymers on the hydrophilic properties of the skin // Uzbek chemical journal. 2007.- No. 5.- C. 16-20. [in Russian].
2. Amirsaidov T. E., Kadirov T. Zh., Ruziev R. R. Monomeric divinyl quaternary salts in the processes of filling natural skins. // Scientific Symposium ofYoung Scientists "Chemistry and Physics of High-Molecular Compounds", - Tashkent, 2002.-May 30,- P. 114-115. [in Russian].
3. Chursin V. I., Levachev S. M. Influence of synthesis conditions on the dispersion of carbamide-formaldehyde tanning agents. // Plastic masses.- Moscow, 2006.- No. 3.- P. 26-27. [in Russian].
