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SOLVENTS AS THE MAIN FACTOR OF REGULATION OF VISCOSITY AND FOAMING IN EPOXY OLIGOMERS SYSTEM Absoatov Yu-К. (Republic of Uzbekistan)
Absoatov Yusuf Kadirovich - Applicant, PHYSICAL CHEMISTRY LABORATORY, NATIONAL UNIVERSITY OF UZBEKISTAN NAMED AFTER MIRZO ULUGBEK, TASHKENT, REPUBLIC OF UZBEKISTAN
Abstract: the outcomes of some technological characteristics of anticorrosive coatings based on modified epoxy resins are presented. Dependence curves of mechanical property indexes: tensile strength, relative elongation of cured coatings on the quantity of solvent pass through the maximum. The maximum on the curve for commercial epoxy ED-20 corresponds to the value of 5 - 6%, while for the modified epoxyurethane and silicon epoxyurethane oligomers correspond to 7 and 8 - 8,5%. A further increase in solvent content significantly reduces the ultimate strength and other mechanical characteristics, probably due to residual solvent amounts that do not have time to vaporize during curing, thereby reducing the ultimate strength, destructive stress in compression and relative elongation of polymer coatings.
Keywords: epoxy resin, viability of coatings, modification, epoxyuratene resin, silicon epoxyuratene resin, relative elongation, ultimate tensile strength.
РАСТВОРИТЕЛИ КАК ОСНОВНОЙ ФАКТОР РЕГУЛИРОВАНИЯ ВЯЗКОСТИ И ПЕНООБРАЗОВАНИЯ В СИСТЕМЕ ЭПОКСИДНЫХ ОЛИГОМЕРОВ Абсоатов Ю.К. (Республика Узбекистан)
Абсоатов Юсуф Кадирович - соискатель, лаборатория физической химии, Национальный университет Узбекистана им. Мирзо Улугбека, г. Ташкент, Республика Узбекистан
Аннотация: приводятся результаты исследования некоторых технологических характеристик антикоррозионных покрытий на основе модифицированных эпоксидных смол. Кривые зависимости показателей механических характеристик: предел прочности при растяжении, относительное удлинение отверженных покрытий от количеств растворителя проходят через максимум. Максимум на кривой для товарной эпоксидной ЭД-20 соответствует значению 5 - 6%, в то время как для модифицированных эпоксиуретанового и кремнийэпоксиуретанового олигомера соответствуют 7 и 8 - 8,5%. Дальнейшее повышение содержания растворителя значительно снижает предел прочности и др. механических характеристик, что, вероятно, связано с остаточными количествами растворителя, которые при отверждении не успевают улетучиваться, тем самым снижая показатели предела прочности, разрушающего напряжения при сжатии и относительного удлинения полимерных покрытий. Ключевые слова: эпоксидная смола, жизнеспособность покрытий, модифицирование, эпоксиуратеновая смола, кремнийэпоксиуратновая смола, относительное удлинение, предел прочности.
Over the last century, the interest and demand for organic and non-organic protective coatings has increased dramatically. Anticorrosive protective coatings based on epoxy resins (epoxyurethane, epoxysilane, phosphorus epoxy, etc.) are widely used due to their high moisture, chemical and thermal resistance, frost resistance, resistance to various mechanical impacts. Coatings are indispensable anti-destructive agents from food to construction industry, in petrochemical production and pharmaceutical industry, in light industry branches [1], machine building and shipbuilding, radioelectronic industry. Methods of producing artificial amber by mixing epoxy resin, rosin and shellac in certain proportions are widely known. Designers never cease to amaze by creating new materials ranging from ordinary bottles to jewelry based on epoxy resins and a combination of natural or synthetic additives.
Numerous coevals of epoxy resin (ebonite, wood resin, polystyrene, etc.) have already been displaced from the list of industrially relevant polymers, while there are no analogues for epoxy resin that could send it to the list of industrial chronicles. The acrylic resins that have been developed cannot be overlooked: they are easier to work with! However, even they are not able to displace the most widely used resins [2].
Diane epoxy resins are divided into three main types: liquid, low-melting and high-melting resins. Liquid resins have lower viscosity and density values and such varieties as ED-24, ED-22, ED-20 and ED-20C belong to this group. ED-16, ED-16S, ED-14 and ED-40 correspond to the second group and ED-13, ED-10 and others to the third group [3].
The presence of epoxy and hydroxyl groups in the composition contributes to their hardening as a result of reaction with various substances, and the number of these materials is increasing every day [3].
The curing of epoxy resins is a complex process and can involve polycondensation or polymerization reactions. The scientific and practical studies carried out so far have helped to establish the mechanism of these transformations [4].
Aliphatic and aromatic amines, acids and anhydrides are widely used as modern hardeners. Compounds with a hydroxyl group initiate the reaction of epoxides with nucleophilic reagents, i.e., amines [5]. The mechanism of this reaction was first proposed by Smith [6].
The authors are conducting research on the creation of modified epoxy oligomers characterized by increased adhesion abilities and anti-corrosion characteristics. Earlier researches showed some data on synthesis processes of hydroxylurethane (HUS) and silicium diurethane (SDS) based on non-toxic 1,2-propylene carbonate and 1,3-propylenediamine which were successfully used for modification of commercial ED-20 epoxy resin [7]. In the present study the aim was to establish the effect of solvent quantities on the characteristics of anticorrosive coatings based on modified epoxy resins: EUS - epoxy-urethane oligomer and SiEUS - silicon containing epoxy-urethane oligomer.
As shown in earlier outcomes [7], as well as literature data for all resin systems are characterized by certain values of porosity. If we take into account their activity and the fact that during the industrial preparation intensive mechanical agitation of the mixture is used, it is impossible to conduct this process without increasing the foaming in the system, and as a consequence, an increase in the degree of porosity. To increase the yield of adsorbed gas particles it is necessary to reduce the surface energy and viscosity of the system. To reduce the viscosity of the system in the industry hydrophobic solvents are used. Various solvents (xylene, toluene, metylethyl ketone, gasoline, etc.) make the epoxy oligomer system more hydrophobic. When the solvent (xylene) is added to the epoxy system, the first change that can be observed visually is the liquefaction of the system and it becomes more fluid. Viscosity of the system decreases due to the decrease in the number of interactions between the active centers -structure formers (urethane, epoxy, hydroxyl groups), which leads to increased viability of the oligomeric system. The change of viability duration (cured at 80°Q from the amount of xylene in the system is shown in Fig. 1.
-ЭД-20 -ЭУС3 -SiЭУС3
Количество ксилола, %
Fig. 1. Dependence of viability duration on the amount of solvent in the system
The curves of dependence of the duration of viability on the amounts of solvent have almost identical forms, only differing in values, which shows the same nature of the interaction between the solvent and matrix molecules.
-ЭД-20 -ЭУС3 -Б1ЭУС3
15,5
(D
S
и
(D
И S
ч
£ (D
о и
Л
ч
(D
и
о о и н О
15 14,5
14
13,5
13 12,5
12
11,5 11
4 6 8
Количество ксилола, %
10
12
А)
70
65
60
55
50
45
5 40 ч
(D
С 35
ЭД-20
ЭУС3
Б1ЭУС3
4 6 8
Количество ксилола, %
10
12
B)
Fig. 2. Dependence of (a) relative elongation; (2) ultimate strength on the amounts of xylene
The curves of dependence (Fig. 2) of mechanical characteristics (ultimate tensile strength, relative elongation) of hardened coatings on the amount of solvent pass through the maximum. The maximum on the curve for ED-20 corresponds to a value of 5 - 6%, while for the modified EUS3 and SiEUS3 correspond to 7 and 8 - 8.5%. A further increase in solvent content significantly reduces the tensile strength and other mechanical characteristics, probably due to residual amounts of solvent that do not have time to volatilize during curing, thereby reducing the tensile strength, compressive breaking stress and relative elongation of polymer coatings.
Thus, the conducted studies contributed to establishing the optimal amount of xylene as a solvent for epoxy resin and its modified forms, which improves the mechanical characteristics of hardened coatings based on them.
References / Список литературы
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6. Lizunov D.A. Razrabotka vysokoprochnykh ugleplastikov na osnove epoksisoderzhashchikh oligomerov. dis. cand. of tech. sci. M., 2014. P. 237.
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