Dr. Mark D. Soucek
Professor of Polymer Engineering
Professor of Chemistry
Department of Polymer Engineering
Phone: 330-972-2583
Email: msoucek@uakron.edu
Research Areas
- UV-Curable Coatings
- Ureas, Urethanes, Polyesters
- Waterborne Coatings
- Space Coatings
- Powder Coatings Center
- Dry Oils and Ceramer Coatings
Waterborne Coatings
With the steadily mounting environmental concerns of society, the use of solvents in coatings systems is becoming less favorable. This has caused a push towards the use of water as the solvent of choice. The common method used to increase the water solubility of polymers in water is to neutralize the carboxylic acids on the polymer backbone, with a tertiary amine, to increase the hydrophilic nature of the polymer. Unfortunately, the presence of the amine can catalyze the homopolymerization and crosslinking reactions of most epoxides. As a consequence, it is difficult to utilize an unreacted epoxide in waterborne coatings.
Waterborne Epoxides
The two primary classes of epoxides used for coatings are phenyl glycidyl epoxides and cycloaliphatic epoxides. The diglycidyl ether of Bisphenol-A (BPA) has traditionally dominated much of the application of epoxy resins in industry. However, homopolymerization of glycidyl epoxides are catalyzed by tertiary amines, and this precludes usage in most waterborne coating systems. Cycloaliphatic epoxides, however, do not homopolymerize in the presence of tertiary amines, and as a consequence are good candidates for waterborne coatings systems. An example of a cycloaliphatic epoxide crosslinker is shown in Figure 1. The cycloaliphatic epoxide consists of a oxirane ring fused to a cyclohexyl ring. The result is a twisted boat confirmation shown in Figure 2. The order of reactivity for cycloaliphatic epoxides is directly opposite of glycidyl epoxides (carboxylic acids > alcohols > amines). It is postulated that the reactivity of cycloaliphatic epoxide is a direct consequence of the its fused ring structure.
Scheme 1: A typical commercial cycloaliphatic epoxide
Previous work in this laboratory has focused upon the competitive reaction kinetics of cycloaliphatic epoxides with carboxylic acids and alcohols. These competitive reaction kinetics were used to model the competitive crosslinking reactions of waterborne acrylic latex resins with cycloaliphatic epoxides as shown in Scheme I. It has been shown that waterborne crosslinking reactions are catalyzed by strong acids and that the cycloaliphatic epoxides are reactive towards both hydroxyl and carboxyl nucleophiles. Previous work has also shown that tertiary amines function only as a spectator ion in the competitive reactions of cycloaliphatic epoxides.
Scheme 2: Steric factors influencing reactivity of epoxide
Work on the development of this emerging waterborne technology into airplane topcoats has already begun. The results of the model compound studies are presently being tested using model latexes. A series of hydroxyl and carboxyl functionalized latexes are being used to investigate the crosslinking reaction of the cycloaliphatic diepoxide within a polymeric based media. The goal of this study is to link the model compound study with the polymeric system it models. From the results of these model latex and model compound studies, latexes that have both hydroxyl and carboxyl groups have been prepared, and screened for usage as topcoats for automobiles and aircraft. The next phase of this project involves the separation of functional groups using core-shell latex methodology.
The investigation of the effects of separating functional groups via a core-shell approach continues to yield interesting results. When the core is hydroxyl functionalized and the shell is carboxylic functionalized, the approach afforded excellent coatings properties and good pot-life stability (See Scheme 3). The addition of the diepoxide monomer to the core-shell latex system was also studied. We found that we could add the diepoxide as an alcoholic solution, an emulsion, or add it during the polymerization of the latex core (See Scheme 4). The best balance of properties was obtained when the half of the diepoxide was added during the polymerization and the other half post-added as an alcoholic solution.
Scheme 3: Cycloaliphatic diepoxide crosslinkable core/shell latex particle
Scheme 4: Proposed effect of introduccion modes of crosslinker
1. Wu, S. and Soucek, M. D.(1997) “Cycloaliphatic Epoxide Crosslinkable Carbonyl Functionalized Acrylic Latexes” Polym. Prepr., vol. 38(1) , 492.
2. Wu, S.; Soucek, M.D. (1997) “Model Compound Studies for Acrylic Latex Crosslinking Reactions with Cycloaliphatic Epoxides” J. Coat. Technol. vol. 69(869), 43.
3. Wu, S.; Soucek, M.D. (1998) “Kinetic Modelling of Crosslinking Reations for Cycloaliphatic Epoxides with Hydroxyl- and Carboxyl-Functionalized Acrylic Copolymers: 1. pH and Temperature Effects” Polymer vol. 39(23), 5747.
4. Wu, S.; Soucek, M.D. (1998) “Oligomerization Mechanism of Cyclohexene oxide” Polymer vol. 39(15), 3583.
5. Soucek, M.D.; Abu-Shanab, O. L.; Anderson, C. D.; Wu, S. (1998) “Kinetic Modeling of the Crosslinking Reaction of Cycloaliphatic Epoxides with Carboxyl Functionalized Acrylic Resins: Hammett Treatment of Cycloaliphatic Epoxides” Macromol. Chem. Phys. 199, 1035.
6. Wu, S.; Jorgensen, J.D.; Skaja, A.D.; Williams, J. P.; Soucek, M.D. (1999) “Effects of Sulphonic and Phosphonic Acrylic Monomers on the Crosslinking of Acrylic Latexes with Cycloaliphatic Epoxide” Prog. Org. Coat. Vol. 36, 21.
7. Wu, S.; Soucek, M.D. (2000) “Crosslinking of Model Latexes with Cycloaliphatic Diepoxides” Polymer, 41(6), 2017.
8. Wu, S.; Jorgensen, J.D.; Soucek, M.D. (2000) “Synthesis of Model Acrylic Latexes for Crosslinking with Cycloaliphatic Diepoxides” Polymer, 41(1), 81.
9. Soucek, M. D.; Teng, G.; Wu, S. (2001) “Cycloaliphatic Epoxide Crosslinkable Core-Shell Latexes: A New Strategy for Waterborne Epoxide Coatings” J. Coat. Technol. Vol. 73(921), 117.
10. Teng, G.; Soucek, M.D. (2001) “Synthesis and Characterization of Cycloaliphatic Diepoxide Crosslinkable Core-Shell Latexes” Polymer, 42, 2849.
11. Teng, G.; Soucek, M.D. (2003) “Effect of Addition Mode of Cycloaliphatic Diepoxide on the Morphology and Film Properties of Crosslinkable Core-Shell Latex” J. Appl. Poly. Sci. 88(2), 245.
12. Teng, G.; Soucek, M.D. (2002) “Effect of Introduction Mode of Hydroxyl Functionality on Morphology and Film Properties of Cycloaliphatic Diepoxide Crosslinkable Core-Shell Latex” J. Poly. Sci.: Part A 40, 4256.
1. Wu, S. and Soucek, M. D.(1997) “Cycloaliphatic Epoxide Crosslinkable Carbonyl Functionalized Acrylic Latexes” Polym. Prepr., vol. 38(1) , 492.
Cycloaliphatic Epoxide Crosslinkable Carbonyl Functionalized Acrylic Latexes
Abstract
Thermoset acrylic latexes were synthesized using methyl methacrylate (MMA), butyl acrylate (BA), acrylic acid (AA), and 2-sulfoethyl methacrylate (SEM). The resulting latex was crosslinked with a cycloaliphatic diepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate. The crosslinking reaction of the coating films was investigated by gel content, IR, TGA, and DSC. The differential scanning calorimeter (DSC) revealed an exothermic peak indicative of a crosslinking reaction. An increase in the temperature of the glass transition (Tg) and the thermal stability of the crosslinked coatings were observed. Furthermore, the pencil hardness, solvent resistance, and the reverse impact resistance were shown to increase significantly compared with the un-crosslinked acrylic coating films. From these results, it was postulated that the cycloaliphatic diepoxide reacted with the carboxylic group (AA) of the latex copolymer to form the crosslinked latex films.
2. Wu, S.; Soucek, M.D. (1997) “Model Compound Studies for Acrylic Latex Crosslinking Reactions with Cycloaliphatic Epoxides” J. Coat. Technol. vol. 69(869), 43.
Model Compound Study for Acrylic Latex Crosslinking Reactions with Cycloaliphatic Epoxides
Abstract
Cyclohexene oxide, methanol and acetic acid were used as model compounds to study the competitive crosslinking reactions of cycloaliphatic diepoxides with hydroxyl and carboxyl functionalized acrylic copolymers. Model reactions were performed as a function of molar ratio, pH, and temperature. At a 2:1:1 molar ratio of epoxide to hydroxyl to carboxyl, the formation of the primary ether and ester linkages were found to be the major crosslinking reactions. By increasing the molar ratio to 3:1:1, the formation of the secondary ether and ester products were significantly enhanced. As the pH of the media decreased, the rate of the crosslinking reactions increased, and generally ester products were formed preferentially to ether products. A temperature dependence of the rate of reactions were generally pronounced at higher pH.
3. Wu, S.; Soucek, M.D. (1998) “Kinetic Modelling of Crosslinking Reations for Cycloaliphatic Epoxides with Hydroxyl- and Carboxyl-Functionalized Acrylic Copolymers: 1. pH and Temperature Effects” Polymer vol. 39(23), 5747.
Kinetic Modeling of Crosslinking Reactions for Cycloaliphatic Epoxides with Hydroxyl and Carboxyl Functionalized Acrylic Copolymers:
Part I. pH and Temperature Effects
AbstractThe crosslinking kinetics and the reaction mechanism of cycloaliphatic epoxides with both hydroxyl and carboxyl functional groups were studied using cyclohexene oxide, methanol, and acetic acid as model compounds. The reactions of cyclohexene oxide with methanol and acetic acid were performed as a function of pH and temperature. The major products isolated from the reaction system were trans -2-acetoxyl cyclohexanoland trans -2-methoxyl cyclohexenol. However, none of the corresponding cis isomer was observed. The reaction order was determined to be first order in acetic acid and cyclohexene oxide for trans- 2-acetoxyl cyclohexenol, and first order in methanol, cyclohexene oxide, and proton concentration for trans -2-methoxyl cyclohexenol, respectively. The reaction rate constants, reaction orders, activation energies, activation enthalpies and entropies for the formation of the products in the reactions were determined for the competitive system. Based upon the stereochemistry of the products and the kinetic data, an A-2 type mechanism is proposed for both major products.
4. Wu, S.; Soucek, M.D. (1998) “Oligomerization Mechanism of Cyclohexene oxide” Polymer vol. 39(15), 3583.
Oligomerization Mechanism of Cyclohexene Oxide
AbstractOligomerization of cyclohexene oxide was studied in the presence of two competitive nucleophiles (methanol and acetic acid). The resulting oligomers, 2-methoxyl -2’-hydroxyl-dicyclohexyl ether (II) and 2-acetoxyl-2’-hydroxyl-dicyclohexyl ether (IV), were isolated and spectroscopically characterized. The formation of these oligomers were evaluated as a function of the reactant molar ratio, pH, and temperature. The reaction rate constants, and Arrhenius parameters for the formation of the oligomers were determined over a pH range of 4 to 7. The reaction rates for the formation of these oligomers exhibited a second order dependence on the concentration of cyclohexene oxide, and first order dependence on the nucleophile and proton concentration, respectively. The major reaction pathway proposed for the formation of the cyclohexene oxide oligomers was via an activated chain end complex. The propagation of the activated chain end complex was then terminated by nucleophilic attack (methanol or acetic acid).
5. Soucek, M.D.; Abu-Shanab, O. L.; Anderson, C. D.; Wu, S. (1998) “Kinetic Modeling of the Crosslinking Reaction of Cycloaliphatic Epoxides with Carboxyl Functionalized Acrylic Resins: Hammett Treatment of Cycloaliphatic Epoxides” Macromol. Chem. Phys. 199, 1035.
Kinetic Modeling of the Crosslinking Reaction of Cycloaliphatic Epoxides with Carboxyl Functionalized Acrylic Resins: Hammett Treatment of Cycloaliphatic Epoxides
Abstract
Cyclohexene-oxide and benzoic/substituted benzoic acids were used as model compounds to study the reactivity of cycloaliphatic diepoxides with carboxyl functionalized polymers. A s- r Hammett treatment of cycloalphatic epoxides with substituted benzoic acids was used to investigate the reaction mechanism(s) of ester formation. The catalytic dependence on the acid strength was obtained via a H o Hammett-Deyrup acidity function. The s- r Hammett treatment resulted in a positive r indicating that the transition state or the activated complex has a developing negative charge. This suggests that only the dissociated benzoic acid (or substitued benozic acids) is the attacking nucleophile.
6. Wu, S.; Jorgensen, J.D.; Skaja, A.D.; Williams, J. P.; Soucek, M.D. (1999) “Effects of Sulphonic and Phosphonic Acrylic Monomers on the Crosslinking of Acrylic Latexes with Cycloaliphatic Epoxide” Prog. Org. Coat. Vol. 36, 21.
Effects of Sulphonic and Phosphonic Acrylic Monomers on the Crosslinking of Acrylic Latexes with Cycloaliphatic Epoxide
Abstract
Two model acrylic latexes were synthesized using methyl methacrylate (MMA) and butyl acrylate (BA) with methacrylic acid (MAA) or 2- hydroxyethyl methacrylate (HEMA). The MAA or HEMA were incorporated to provide the latexes with carboxyl and hydroxyl functionality, respectively. A cycloaliphatic diepoxide (3, 4-epoxycyclohexyl methyl-3’, 4’-epoxycyclo- hexane carboxylate) was used as a crosslinker for both the latexes. The crosslinking of the latexes with the diepoxide was catalyzed using a copolymerizable or free sulphonic or phosphonic acids. The copolymerizable acids (2-sulfoethyl methacrylate (SEM) and acid phosphoxyethyl methacrylate (PEM)) were added during the latex synthesis. The free acids ( r-toluene sulphonic acid (TsOH) and phenylphosphonic acid (PPA)) were added into the latex emulsion shortly before crosslinking. The crosslinked coatings were evaluated in terms of water absorption, gel content, and pull-off adhesion. The crosslinking of the hydroxyl functional latex coatings with the cycloaliphatic epoxide required an acid catalyst, whereas the crosslinking of the carboxyl latex coatings did not need an acid catalyst. Sulphonic and phosphonic acrylic acid monomers not only functioned as catalysts for the crosslinking reactions, but also improved the adhesion and freeze-thaw stability of the latex coatings. In addition, neutralization of the acid catalysts led to reduction of the crosslinker hydrolysis, and consequently enhanced the overall coating properties.
7. Wu, S.; Soucek, M.D. (2000) “Crosslinking of Model Latexes with Cycloaliphatic Diepoxides” Polymer, 41(6), 2017.
Abstract
Cycloaliphatic epoxide thermosetting acrylic latexes were synthesized using methyl methacrylate (MMA) and butyl acrylate (BA) with methacrylic acid (MAA) or 2- hydroxyethyl methacrylate (HEMA). The MAA or HEMA was incorporated to provide the latexes with carboxyl or hydroxyl functionality, respectively. A cycloaliphatic diepoxide (3, 4-epoxycyclohexyl methyl-3’, 4’-epoxycyclohexane carboxylate) was used with hydroxyl or carboxyl functional latexs to formulate thermosetting acrylic latex coatings. The coatings were crosslinked as a function of temperature, time, and the amount of the crosslinker. The crosslinking reactions were monitored using DSC (differential scanning calorimeter), IR (infrared), and DMTA (dynamic mechanical thermal analysis). The coatings properties were evaluated in terms of water absorption, gel content, pencil hardness, and pull-off adhesion. The morphology of the latex coatings was studied using AFM (atomic force microscopy). The spectroscopic and rheological data showed that the cycloaliphatic diepoxide effectively crosslinked both the hydroxyl and carboxyl functional latexes. Carboxyl latex coatings were more reactive than hydroxyl latex coatings. The water resistance, solvent resistance, pencil hardness, and pull-off adhesion improved with the crosslinking temperature, time, and the amount of the crosslinker.
8. Wu, S.; Jorgensen, J.D.; Soucek, M.D. (2000) “Synthesis of Model Acrylic Latexes for Crosslinking with Cycloaliphatic Diepoxides” Polymer, 41(1), 81.
Synthesis of Model Acrylic Latexes for Crosslinking with Cycloaliphatic Diepoxides
Abstract
Two model acrylic latex systems were synthesized. One latex system was carboxyl functional, and prepared using methyl methacrylate (MMA) and butyl acrylate (BA) with methacrylic acid (MAA). The second latex system was hydroxyl functional, and prepared using methyl methacrylate (MMA) and butyl acrylate (BA) with 2- hydroxyethyl methacrylate (HEMA). Both the resultant latexes were crosslinked with a cycloaliphatic diepoxide (3, 4-epoxycyclohexyl methyl-3’, 4’-epoxycyclohexane carboxylate). Dynamic mechanical thermal analysis (DMTA) and dynamic scanning calorimeter (DSC) were used to study the rheological and thermal properties of the crosslinked coatings. The crosslinking and the coating properties were evaluated in terms of water absorption, gel content, Tukon hardness, pull-off adhesion, impact resistance, conical mandrel flexibility, and hydrolytic stability. The increase in the latex carboxyl or hydroxyl functionality and glass transition temperature resulted in enhancement of the overall coating properties. However, a balance of the crosslink density and the glass transition temperature was necessary for both good adhesion and impact resistance. In addition, the carboxyl functional acrylic latexes displayed better overall coating properties than the hydroxyl functional acrylic latexes, and the polarity and steric hindrance of the ester crosslinks may play important functions in the observed properties.
9. Soucek, M. D.; Teng, G.; Wu, S. (2001) “Cycloaliphatic Epoxide Crosslinkable Core-Shell Latexes: A New Strategy for Waterborne Epoxide Coatings” J. Coat. Technol. Vol. 73(921), 117.
Cycloaliphatic Epoxide Crosslinkable Core-Shell Latexes: A New Strategy for Waterborne Epoxide Coatings
AbstractNew core-shell acrylic latexes designed for crosslinking with cycloaliphatic diepoxides were prepared. The core consisted of methyl methacrylate (MMA), butyl acrylate (BA), 2-hydroxyethyl methacrylate (HEMA), and the shell MMA, BA, and methacrylic acid (MAA). A strong acid acrylate was incorporated into the shell to catalyze the crosslinking reactions. The diepoxide was embedded in core of the latex, which contained the less reactive functional monomer HEMA. The pot-life stability of epoxide was shown to be dependent on latex morphology, initiator system, and reaction conditions. The latexes were crosslinked with cycloaliphatic diepoxide added as an emulsion or as solution (organic solvent).
10. Teng, G.; Soucek, M.D. (2001) “Synthesis and Characterization of Cycloaliphatic Diepoxide Crosslinkable Core-Shell Latexes” Polymer, 42, 2849.
Abstract
New core-shell acrylic latexes designed for crosslinking with cycloaliphatic diepoxides were prepared. The core was prepared using methyl methacrylate, butyl acrylate, 2-hydroxyethyl methacrylate; and the shell with methyl methacrylate, butyl acrylate, and methacrylic acid. A strong acid acrylate was incorporated into the shell to catalyze the crosslinking reactions, and provide freeze-thaw stability. The crosslinker was co-emulsified with the monomer and added during the latex preparation. The pot-life stability of epoxide was shown to be dependent on latex morphology, initiator system, and reaction conditions. The preparation of stable latex with minimum pre-mature crosslinking required the basic reaction condition, and lower shell polymerization temperature via a redox initiator system. Otherwise, either coagulation or higher level of pre-mature crosslinking occurred.
11. Teng, G.; Soucek, M.D. (2003) “Effect of Addition Mode of Cycloaliphatic Diepoxide on the Morphology and Film Properties of Crosslinkable Core-Shell Latex” J. Appl. Poly. Sci. 88(2), 245.
Ganghua Teng, Mark D. Soucek*
Department of Polymers Engineering , University of Akron, Akron, Ohio 44325
Xiaofan F. Yang, Dennis E. Tallman
Department of Chemistry, North Dakota State University, Fargo, ND 58105
AbstractCore-shell latexes designed for crosslinking with the cycloaliphatic diepoxide were synthesized. The core contained methyl methacrylate, butyl acrylate, and 2-hydroxyethyl methacrylate, and the shell was prepared using methyl methacrylate, butyl acrylate, and methacrylic acid. The crosslinker was co-emulsified with the monomer and added during the latex preparation, or added after the polymerization either as an emulsion or in an organic solvent. The morphology of the latex was studied using atomic force microscopy (AFM) and transmission electron microscopy (TEM). Titration was used to establish the acid distribution. The water absorption, tensile and viscoelastic properties of the latex films were investigated as a function of addition mode of the cycloaliphatic diepoxide crosslinker. The solution approach generally provided better mechanical properties than the emulsion approach, and addition of the epoxide during the polymerization lowered the water adsorption and hardness.
Key words: cycloaliphatic epoxide; core-shell latex; crosslinking; coatings; mechanical properties
12. Teng, G.; Soucek, M.D. (2002) “Effect of Introduction Mode of Hydroxyl Functionality on Morphology and Film Properties of Cycloaliphatic Diepoxide Crosslinkable Core-Shell Latex” J. Poly. Sci.: Part A 40, 4256.
Effect of Introduction Mode of Hydroxyl Functionality on Morphology and Film Properties of Cycloaliphatic Diepoxide Crosslinkable Core-Shell Latex
Ganghua Teng and Mark D. Soucek *
Department of Polymers Engineering , University of Akron, Akron, Ohio 44325
Abstract
Three series of core-shell hydroxyl functionalized latexes were synthesized, and then crosslinked with a cycloaliphatic diepoxide. The same amount of hydroxyl functional monomer was added during the core stage, shell stage, or partitioned equally between the core and shell. The morphology of the latexes was studied using transmission electron microscopy and contact angle measurement. The stress-strain behavior, viscoelastic properties, and water adsorption were evaluated for the latex films as a function of hydroxyl location. The location of hydroxyl groups within latex particles appeared to be dependent on the introduction mode of hydroxyl functional monomers. The introduction of hydroxyl groups during the shell polymerization resulted in a higher crosslinking density, but a lower Tukon hardness and tensile properties. Not surprisingly, distribution of hydroxyl groups in both core and shell polymerization provided lowest water adsorption and impact resistance, and highest tensile elongation.