1. In organic compounds, since the carbon atom can make four bonds, it can easily bond with both other carbon atoms and with other atoms. Today, carbon has more than 8 million known compounds and new ones are added to them every year. Each different arrangement of atoms in an organic molecule leads to the formation of a different compound. Hydrogen, oxygen, sulfur, nitrogen, fluorine, chlorine, bromine, iodine and phosphorus can be connected to carbon atoms in an organic compound that can be in chain and ring structure .
2. The formation of an organic or inorganic compound takes place depending on the location of the elements in the Paulingin Electronegativity Scale . Accordingly, if the electronegativity difference between the two atoms is greater than 1.7 , an ionic bond is formed between these two atoms. Again, if the electronegativity difference is between 0.5-1.6, the formation of "polar covalent bond" and between 0.0-0.4, "apolar covalent bonds" can be mentioned.
3. In leather production, surfactant use is the most common in the following processes;
a) Wetting-Softening
b) Liming
c) Degreasing
d) Painting
e) Lubrication
f) Finishing
4. Surfactants are substances that significantly change the surface or interface properties of a liquid in which they are dissolved in very small quantities , and these properties can be understood by looking at their structure . Surfactant molecules are bilateral and bidirectional orientation materials, and with these features , their desire to take part in different phases becomes evident.
5. Surfactants are characterized by forming layers directed at the phase interfaces depending on their chemical structure . They are also known as amphipathic or amphiphilic compounds. This definition is made based on the asymmetry occurring in the molecule since they contain chemical groups with different structures and features .
6. Water molecular structure due to the unbalanced oxygen portion of the molecule based on the molecular structure of the hydrogen terminal is more negative and a Polarization shows. Accordingly, water is a very good solvent for polar materials . In addition, the surface tension of water at 20 0 C is 73 dyn / cm.
7. According to the physicochemical rules, the molar free energy of the surface region of the liquid is higher than the molecules in the other part of the liquid and this is called the surface tension. The unit in the SI system is Nm -1 , and the unit in the CGS system is dyn / cm .
8. One of the important basic features of a surfactant is the tendency to gather at the interfaces . The stronger this tendency in the interfaces, the better the surfactant properties. This effect depends on the structure of the surfactant as well as the structure of the two phases that meet at the interface . Thus, there is a limit in the effect of reducing the surface or interface tension with the surfactant and there is no surfactant for universal use .
9. The hydrophobic portion of the surfactant can be in the form of linear or branched alkyl groups. The length of the chain, the degree of branching and the location of the polar group on the chain are important parameters for the physicochemical properties of a surfactant. The polar group or hydrophilic part may be ionic or non-ionic in nature. For non-ionic surfactants , different physicochemical properties can be obtained by changing the size of the polar head group as desired .
10. In the use of surfactants, a special packaging created to stop the hydrophobic groups in contact with water and thereby reduce the free energy of the system is called micelle formation or micelization, and this occurs depending on concentration . The concentration at which this phenomenon begins to occur; It is called the critical micelle concentration and is denoted by the term CMC .
11. The most important and basic classification of surfactants is made based on the load of the polar head group . According to this; It is the most common thought and practice to classify surfactants as anionic, cationic, nonionic and zwitterionic . However, surfactants containing both a group such as sulfate, phosphate or carboxylate, and a polyoxyethylene chain are also widely available. In this case, both anionic and both nonionic properties are in the same molecule.
12. The soap, which is the most important group of anionic surfactants, is in the structure of RCOO - M + and is generally saturated with sodium and potassium. However, in surfactants, collapses are observed in the environment where di- and trivalent cations are present and at high NaCl concentrations. To prevent this, aminocarboxylates can be used without any problems as a variant of this group .
13. Aliphatic paraffin sulfonates produced from refinery hydrocarbons, petroleum sulfonates and olefin sulfonates derived from selected petroleum distillate fractions are the most important examples of anionic surfactants . In this group of surfactants, the group R has the general formula RSO 3 Na , which is biodegradable or non-degradable hydrocarbon . Here, the carbon-sulfur bond is not sensitive to oxidation and hydrolysis under normal use conditions . Today, LABS Linear alkyl benzol sulfonates are preferred in detergents with their low cost, light color and easy degradation.
14. The hydrophilic group in sulfates is -OSO 3 . The molecule can be easily hydrolyzed due to this kind of connection of sulfur with the carbon atom of the chain . In the synthesis of sulfates, it generally involves esterification of an alcohol with sulfuric acid, sulfur trioxide or chlorine sulfonic acid or the addition of internal sulfuric acid to an ethylenic double bond .
15. Fatty alcohol sulfates or also alkyl sulfates are the first synthetic surfactants used in cleaning products. While hydrophobic groups have been obtained by the reduction of fatty acids or esters for a long time , these alcohols are today produced by various catalytic reactions using ethylene as the starting material . This process , also called the Ziegler process , gives even numbered alcohols equivalent to those obtained from natural fatty acids . The advantage of this is that a desired chain length product can be obtained and alcohols can be mixed in almost any ratio.
16. The ether obtained when the fatty alcohol is ethoxylated still carries an end OH group, and from this point, the molecule is sulfated to obtain alcohol ether sulfates . This class of surfactants has the advantages of both anionic and nonionic surfactants. Generally, 5 or fewer ethylene oxide units are added in the ethoxylation of the fatty alcohol, thus ensuring the effectiveness of the sulfate group in water dissolution.
17. Alkyl ether phosphates are of the class of anionic surfactants and are usually obtained by reaction of a fatty alcohol or alcohol ethoxylate with a phosphorous agent such as phosphorus pentaoxide (P 4 O 10 ) and a mixture of mono- and diesters of phosphoric acid . The physicochemical properties of alkyl phosphate surfactants depend on the ratio of esters .
18. Nonionic surfactants do not form ions in aqueous solutions. As surfactants with polyether and polyhydroxyl groups, they provide solution with polar groups in aqueous solutions. The non-ionic surfactants most commonly used in the leather industry are ethoxylates , which are formed by the binding of ethylene oxide to compounds carrying active hydrogen atoms such as hydroxyl, carboxyl, amido and amino .
19. One of the most important polyol surfactants are sorbitanes. These are derived from monosaccharides . It is known as a sorbitan molecule that the hexitols form a 5 or 6 ring with a two hydroxy etheric bond by heating at acidic pH . Thus, the molecule obtained can be modified over the remaining 4 hydroxyl groups to obtain a surface active agent. If these hydroxyl groups react with other fatty acids, the lipophilic groups of the molecule are formed, and if it reacts with ethylene oxide units, hydrophilic root is added.
20. Cationic surfactants are generally expensive products depending on their production. Their detergent properties are less than that of anionic products, and due to their positive charge absorption onto anionic charged substrates, they have found use as a fabric softener and antistatic agent as well as a hydrophobing agent and corrosion inhibitor . Many other cationic surfactants are used as bactericidal and disinfectant substances .
21. Cationic surfactants are divided into three groups: oil amines, oil amine salts and quarterner ammonium compounds . Amines are three groups, primary, secondary and tertiary amines , depending on the number of alkyl groups to which nitrogen is attached .
22. The simplest zwitterionic surfactant is aminopropionic acid. These are structures very similar to cationic surfactants . It can be dissolved in both acid and alkaline solutions. This surfactant can be represented by the formula RN + CH 2 CH 2 COO - and is used as an antistatic and lubricant in human hair and fabrics .
23. Betaines, sulfobetaines and taurines are very close to cationic surfactants as quaternized products . These surfactants are amphoteric at neutral and alkaline pH and cationic at acidic pH . Since the amino group is quarternized in these surfactants, it carries a continuous cationic charge . The amphoteric structure depends on the ionisation of the caboxyl group .
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