CC BY
17
UDC 678.01
V. F. Kablov, N. A. Keybal, S. N. Bondarenko, K. U. Rudenko, G. E. Zaikov
ASSESSING THE IMPACT OF MODIFICATIONS NEOPRENE ADHESIVES AMINE-CONTAINING
COMPOUNDS THE MECHANISMS TO IMPROVE ADHESION
Keywords: neoprene, amine-containing, adhesion, epoxy compounds, aniline derivatives.
Possible mechanisms for an increase in the adhesion parameters of neopren-based adhesive compositions modified with adhesion promoters on the basis of epoxy compounds and aniline derivatives are studied.
Ключевые слова: неопрен, аминосодержащий, адгезия, эпокси- соединения, производные анилина.
Исследованы возможные механизмы повышения адгезионных свойств неопреновых композиций модифицированных промоторами адгезии на основе эпокси- соединений и производных анилина.
Introduction
Promising adhesion promoters for neopren-based adhesive compositions are compounds containing amino and epoxy groups. As the amine-containing compounds wastes production of aniline are of interest, because they are distinguished by its low volatility and their stable enough structure whose disposal is an urgent environmental challenge. Still wastes of aniline production are characterized by the composition shown in table 1.
According to our study, it was established that, upon interactions between bisphenol A-based ED-20 epoxy resin and still wastes, a product is formed that represents irregular, dark-brown, brittle granules that are well soluble in acetone, toluene, and gasoline and insoluble in water. Some properties of adhesion promoters prepared from this product are listed in Table 2.
Table 1 - Composition of still wastes
Waste component Content, mass parts
Aniline 15-80
Cyclohexylamine 0-10
Toluidine 2-4
Sodium hydroxide 1-3
Diphenylamine 3-20
Methaphenylene diamine 1-3
o, /-Aminophenol 1-6
High-molecular-weight tar compounds 6-45
Table 2 - Properties of adhesion promoter
Parameters
Melting point, °C 7
Mass fraction of volatile substances, % 0.11
Mass fraction of ash, % 0.20
Experimental, Results and Discussion
The data from an IR spectral study confirmed the presence of epoxy, hydroxy, and amine groups, as well as residues of aromatic amines.
As is known, the chlorine atom in 3, 4 units of the neopren macromolecule can easily be transferred to the allyl position (Fig. 1), in which it possesses
enhanced reactivity and is an active site of a polymer chain [1].
The possible scheme of the modification of neopren with developed adhesion promoters is confirmed by the IR spectral data (Fig. 2). As follows from the IR spectra, after the modification of neopren with the developed adhesion promoters, new absorption bands appear in the 1450-1400 cm-1 range, which testifies to the transition from the amine to its salt [2].
Based on the scheme of the modification of neopren and the analysis of published data, we constructed a model of a polymer with enhanced adhesive properties [3]. According to this model, the macromolecule of the adhesive should contain a set of specific functional groups (Fig. 3).
CHi—C—~
С— + NR?
CH NHR?
I
ChbCI
CH
I
CH.N+R^Cl"
—Chb-C—
CH
I
CHiN+HRiCr
Fig. 1 - Scheme of neopren modification
Transmission. %
SO
60
40
20
(a)
_l_I_I_I_I_L_
80
60
40
20 . 0
_l_I_I_L_
0
2800 2200 1600 1000 2800 2200 1600 1000 V, cm-1
Fig. 2 - IR spectra of (a) initial and (b) modified neopren
To verify the validity of this model, we studied the adhesive bonding of vulcanizates based on polyisoprene (SIR) and ethylene-propylene (SREPT)
rubbers using neopren-based adhesive compositions modified with amine-containing adhesion promoters. Using local electron probe microanalysis, we studied the depth of the penetration of 88SA adhesive into vulcanizates during adhesive bonding.
Fig. 3 - Polymer with enhanced adhesive properties: A are the chain segments providing for the crsytallizability of neopren (units of 1,4-trans-isomer; R' is the methylene or ethylene group; R" is the alkylene group providing for the enhanced mobility of X groups; R= is the unsaturated (allyl) fragment (imparts the flexibility to macromolecule); B is the group responsible for the mobility of macromolecules; Hal is the halide atom; and (X19 X2, and X3) are functional groups containing nitrogen atoms, halide atoms, and hydroxyls
As a result, it was revealed that, after modification, the depth of the adhesive penetration into the SIR-based vulcanizate increases (according to chlorine profiling) from 16 to 36 ^m (Fig. 4).
Fig. 4 - The depth of adhesive penetration for the adhesive joints of SIR-based vulcanizates by the data on chlorine distribution profile: (1) initial and (2) modified adhesive
adhesive line with modified adhesive testifies to the diffusion of single segments of neopren macromolecule into the vulcanizate bulk.
Fig. 5 - The depth of adhesive penetration for the adhesive joints of SREPT-based vulcanizates by the data on chlorine distribution profile: (1) initial and (2) modified adhesive
Fig. 6 - Photomicrographs of the sections of adhesive joints of SREPT-based vulcanizates bonded with: (a) 88SA adhesive and (b) modified 88SA adhesive
The surface of the adhesive film containing adhesion promoters is characterized by a more relief structure, which is supported by photomicrographs (Fig. 7). Such a structure favors the better bonding of the adhesive film with the rough surface of vulcanizates, which increases the strength of the adhesive joint. This phenomenon is described by the mechanical theory of adhesion.
Analogous results were obtained for SREPT-based vulcanizates (Fig. 5).
As follows from the analysis of photomicrographs of the sections of adhesive-bonded samples of SIR-based vulcanizate taken with a scanning electron microscope (SEM), upon the modification of adhesive composition with amine-containing substances, the composition diffuses into the vulcanizate depth (Fig. 6). The brighter color of the adhesive line with unmodified adhesive is explained by a complex contrast of image, in which the higher the chlorine concentration is, the brighter the chlorine-containing regions appear to be. The lighter-colored
Fig. 7 - Photomicrographs of adhesive films based on neopren: (a) initial and (b) modified films
Based on the aforementioned, we performed comprehensive studies of the influence of the type and content of adhesion promoters on the strength of adhesive bonding of vulcanizates based on different rubbers to one another and to metal (Table 3).
Table 3 - Comparative strength characteristics of initial and modified adhesive composition of 88SA grade
According to the data obtained, the modified adhesive composition is superior in its adhesion characteristics to current commercial adhesive compositions of the 88 series. It is established that, upon the addition of developed adhesion promoters to neopren-based compositions, the strength of adhesive bonding of vulcanizates based on different rubbers to metal increases by 35-45%, whereas the bond strength of vulcanized rubbers to one another rises by 40-80% (Table 3). These data refer to joints bonded with modified 88SA adhesive. For other adhesives of this
series, e.g., 88NT and 88NP adhesives, the shear and tensile strengths increase to even greater extents.
Conclusion
As a result of studies performed, we revealed possible mechanisms of the improvement of adhesion parameters of neopren-based adhesive compositions modified with adhesion promoters on the basis of epoxy compounds and aniline derivatives.
It was established that, upon the addition of developed adhesion promoters to neopren-based adhesive compositions, chemical modification of neopren macromolecules occurs, which leads to an increase in their flexibility and mobility and, hence, to deeper diffusion into the internal layers of bonded vulcanizates.
References
1. N. D. Zakharov, Chloroprene Rubbers and Related Vulcanizates (Chemistry, Moscow, 1978) [in Russian].
2. L. A. Kazitsina and N. B. Kupletskaya, Application of UV, IR, NMR, and Mass Spectroscopy in Organic Chemistry (Publishing house of the Moscow University, Moscow, 1979) [in Russian].
3. V. L. Vakula and L. M. Pritykin, Physical Chemistry of Polymer Adhesion (Chemistry, Moscow, 1984) [in Russian].
4. N. A. Keibal, S. N. Bondarenko, V. F. Kablov, and I. Y. Goryainov, Study of Mechanisms for the Improvement of Adhesive Properties of Neopren-Based Compositions by Their Modification with Amine-Containing Compounds // Adhesives, Sealants, Technology - 2008. - No. 2. pp. 28-31 [in Russian].
5. N. A. Keibal, S. N. Bondarenko, V. F. Kablov, and I. Y. Goryainov Study of Mechanisms for the Improvement of Adhesive Properties of Neopren-Based Compositions by Their Modification with Amine-Containing Compounds // Polymer Science, Series D. Glues and Sealing Materials -2008, Vol. 1, No. 3, pp. 151-153.
Parameters 88SA adhesive Modified 88SA adhesive
Viscosity by VZ-246 method (0.6 mm), s 27.5 28.1
Shear strength, MPa, of adhesive joints:
SIR-3 + SIR-3 1.02 1.39
SREPT-40 + SREPT-40 1.17 1.59
SRN-18 + SRN-18 0.95 1.38
Tensile strength, MPa, of adhesive joints:
SIR-3 + Steel 3 1.20 1.91
SREPT-40 + Steel 3 1.38 1.93
SRN-18 + Steel 3 0.95 1.78
© V. F. Kablov - Doctor of Engineering, Full Professor, Director, Head of Department, Volzhsky Polytechnical Institute (branch) VSTU, Volzhsky, Russia, N. A. Keybal - Doctor of Engineering, Full Professor, Volzhsky Polytechnical Institute (branch) VSTU, Volzhsky, Russia, S. N. Bondarenko - Ph.D., Associate Professor, Volzhsky Polytechnical Institute (branch) VSTU, Volzhsky, Russia, K. U. Rudenko - Post-Graduate Student, Volzhsky Polytechnical Institute (branch) VSTU, Volzhsky, Russia, G. E. Zaikov -Doctor of Chemistry, Full Professor, Plastics Technology Department, Kazan National Research Technological University, Kazan, Russia, ov_stoyanov@mail.ru.
© В. Ф. Каблов - доктор технических наук, профессор, директор, заведующий кафедрой, Волжский политехнический институт (филиал) ВГТУ; Н. А. Кейбал - доктор технических наук, профессор, Волжский политехнический институт (филиал) ВГТУ; С. Н. Бондаренко - кандидат химических наук, доцент, Волжский политехнический институт (филиал) ВГТУ; К. Ю. Руденко - аспирант, Волжский политехнический институт (филиал) ВГТУ; Г. Е. Заиков - доктор химических наук, профессор, кафедра технологии пластических масс КНИТУ, ov_stoyanov@mail.ru.
