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
Ureas, Urethanes, Polyesters
We have had ongoing projects in the areas of polyurea and polyurethane coatings over the last five years. At first, we modified isocyanates to enhance adhesion. Secondly, we development moisture curing inorganic/organic hybrid coatings which self-assemble into a coating-substrate layer, and a bulk co-continuous phase layer. We also had interest in the synthesis of cycloaliphatic polyesters as the polyol oligomers for polyurethane formation. We studied the general coating properties, and in particular the hydrolytic stability under both acidic and basic conditions. To understand moisture curing polyurea, and polyurethane coatings, we studied the relative reaction rates of aliphatic isocyanates and alkoxyl silanes in the presence of acid, base, and tin catalysts.
As an extension of our ceramer coating studies, we are presently investigating moisture cure polyurethane systems as 'Unicoat' aircraft coatings. The basic concept of our approach is that two crosslinking mechanisms are simultaneously occurring in the presence of atmospheric water. The isocyanate reacts with water to form an amine which immediately crosslinks with another isocyanate group. The inorganic sol-gel crosslinking reaction also occurs via water. The distinguishing feature of the ceramer versus an inorganic/organic hybrid material is inorganic/organic linkage. In the 1K system, the inorganic/organic linkage is via the siloxane modified isocyanurate.
From this approach new inorganic/organic hybrid coatings known as ceramers will be prepared using a polyurethane based self-priming Unicoat system with sol-gel inorganic precursors. The basic concept of the our proposed approach is that both the organic and inorganic phases of the ceramer are crosslinking simultaneously in the presence of atmospheric water. The organic portion crosslinks via a moisture curing mechanism. The isocyanate group of the poylurethane reacts with water to form an amine which immediately crosslinks with another isocyanate group. Concomitantly, the inorganic crosslinking reaction also occurs via water. The sol-gel inorganic portion of the coating will also react with the metal substrate protecting it from oxidation, while the organic polymer (polyurethane) will provide a stable medium for application as a binder. The objective of this research project is to provide better adhesion and corrosion protection to metal substrates utilizing a self-priming Unicoat system. The overall goal of this project is to replace the environmentally hazardous chromium treatment with the environmentally friendly ceramer coatings without sacrificing corrosion protection.
We have developed a modified ceramer approach in our laboratory where TEOS oligomers are used in conjunction with alkoxyl silane modified isoycyanurates (2). The alkoxysilane provides connectivity between the inorganic and organic phases, and the oligomerization of the TEOS inhibits TEOS volatility, and functions as a chromate replacement. Although polyurea coatings have excellent properties, highly crosslinked polyureas coatings do not typically have the damage tolerance that polyurethane coatings do.
Another recent push has been with the development of high solids polyurethanes for exterior usage. Cyclohexyl polyesters were prepared as hydroxyl oligomers for crosslinking with aliphatic isocyanates. Close to 100% solids were achieved with a viscosity conducive to either spray or other means of application. Also, the hydrolytic stability of the cyclo-oligoesters was investigated, and insight to isomeric substitution as a contribution factor was discussed. In addition, Anchimeric versus Steric factors of oligoesters were compared.
1) Johnson, A.J.; Wegner, J.; Soucek, M.D. (2004) “Hydrolytic Stability of Oligoesters: Comparison of Steric with Anchimeric Effects” Eur. Polym. J., 40(12), 2773.
2) Soucek, M.D.; Johnson, A.J. Meeken, L.E. (2004) “Effect of Additional Hydroxyl Functionalities on the Hydroylic Stability of Oligoesters” Macro. Chem. Phys., 204(1), 35.
3) Soucek, M.D.; Johnson, A.J. (2004) “New Intramolecular Effect Observed for Polyesters: An Anomeric Effect” J. Coat. Technol. Res., 1(2), 111.
4) Ni, H; Soucek, M.D. (2002) “Nanostructured Polyurethane Ceramer Coatings for Aircraft” J. Coat. Technol., vol. 74(933), 125.
5) Ni, H; Daum, J.L.; Skaja, A.D; Soucek, M.D. (2002) “Cycloaliphatic Polyester Based High Solids Polyurethane Coatings: II. The Effect of Difunctional Acids” Prog. Org. Coat. vol. 45(1), 49.
6) Ni, H; Johnson, A.H.; Soucek, M.D.; Grant, J.T.; Vreugdenhil, A.J. (2002) “Polyurethane/Polysiloxane Ceramer Coatings: Evaluation of Corrosion Protection” Macromol.Mater.Eng. 287, 470.
7) Ni, H; Daum, J.L.; Soucek, M.D. (2002) “Cycloaliphatic Polyester Based High Solids Polyurethane Coatings: I. The Effect of Difunctional Alcohols” J. Coat. Technol., vol. 74(928), 49.
8) Ni, H; Nash, H. A.; Worden, J. G.; Soucek, M.D. (2002) “Effect of Catalyst on the Reaction of an Aliphatic Isocyanate and Water” J. Poly. Sci.: Part A 40, 1677.
9) Ni, H.; Skaja, A.D.; Soucek, M.D. (2000) “Acid-Catalyzed Moisture-Curing Polyurea/Polysiloxane Ceramer Coatings” Prog. Org. Coat. 40, 175.
10) Ni, H.; Simonsick, Jr., W.J.; Skaja, A.D.; Williams, J. P.; Soucek, M.D. (2000) “Polyurea/Polysiloxane Ceramer Coatings” Prog. Org. Coat. 38 (2), 97.
11) Ni, H.; Skaja, A.D.; Sailer, R.A.; Soucek, M.D. (2000) “Moisture-Curing Alkoxysilane Functionalized Isocyanate Coatings” Macromol. Chem. Phys. 201(6), 722.
12) Ni, H.; Aaserud, D.J.; Simonsick, Jr., W.J.; Soucek, M.D. (2000) “Preparation and Characteristics of Alkoxysilane Functionalized Isocyanurates” Polymer, 41(1), 57.
Hydrolytic Stability of Oligoesters: Comparison of Steric with Anchimeric Effects
M.D. Soucek* and A. H. Johnson, J. Wegner
Department of Polymer Engineering
University of Akron
Akron, OH 44325
A comparison of steric and anchimeric effects on the hydrolytic stability of polyesters was studied. Twelve monomers were selected based on their propensity toward steric and anchimeric interactions: adipic acid, isophthalic acid, phthalic anhydride, hexahydrophthalic anhydride,1,4-cyclohexanedicarboxylic acid, maleic anhydride, ethylene glycol, 1,2-propanediol, 1,3-propanediol 1,4-butanediol, 1,5-pentanediol, and neopentyl glycol. Hydroxyl terminated oligoesters consisting of one diacid and one diol and one hydroxyl terminated oligoester consisting of two diacids and one diol were prepared. The hydrolytic stability was evaluated in an acetone/water solution. The acid number and molecular weight shift were monitored as a function of time. It was found that telechelic groups favor anchimeric interactions, while steric groups determine the rate of hydrolysis for the main chain.
Effect of Additional Hydroxyl Functionality on the Hydrolytic Stability of Oligoesters
Mark D. Soucek, Aaron H. Johnson, Leon E. Meemken,
Department of Polymer Engineering
University of Akron, Akron, OH 44325
Abstract
The addition of trifunctional polyol (trimethylolpropane) to oligoesters comprised of hexahydrophthalic anhydride, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, neopentyl glycol, and 1,4-cyclohexanedimethanol was investigated via accelerated hydrolysis environment. The oligoesters were dissolved in an acetone/water solution, and the hydrolysis was evaluated by monitoring carboxylic acid formation and by measurement of the molecular weight shift by size exclusion chromatograph. Aliquots of the oligoester solution were evaluated intermittently over a 36 week period. Both the initial rate and overall rates of hydrolysis were reported as hydrolysis velocities. The influence of hydroxyl concentration is apparent in the initial velocity of hydrolysis. After the induction period, steric effects appear to be the controlling factor for retardation of main chain scission.
New Intramolecular Effect Observed for Polyesters: An Anomeric Effect
Mark D. Soucek* and Aaron H. Johnson
Department of Polymer Engineering
University of Akron
Akron, OH 44325
A series of polyesters were prepared to evaluate hydrolytic stability as a function of cyclohexyl dibasic acid content. The three cyclohexyl dibasic acids: 1,2; 1,3; and 1,4 were formulated into polyesters with four glycols. The proportion of cis and trans isomers were evaluated via 1H NMR. The hydrolytic stability of short chain polyesters were evaluated in an acetone/water mixture which solubilized the polyesters to mimic oligoester behavior in a thermosetting environment. The rate of hydrolysis was monitored by acid titration and corroborated by GPC. Surprizingly, 1,2-cyclohexyl diacid based polyesters were robust, and 1,3-cyclohexyl diacid based polyesters were the most susceptible to hydrolysis. Evidently, a 1,2-anchimeric effect for cyclohexyl dibasic acid polyesters was not an important consideration, and a 1,3 cyclohexyl ester interaction was. Consequently, an anomeric effect was proposed.
Nanostructured Polyurethane Ceramer Coatings for Aircraft
Mark D. Soucek* and Hai Ni
Department of Polymers and Coatings
North Dakota State University
Fargo, ND 58105
Abstract
New low VOC (volatile organic compounds) polyurethane/oligosiloxane coatings was formulated using, 1,6-hexamethylene diisocyanate (HDI) isocyanurate, alkoxysilane-functionalized HDI isocyanurate, tetraethyl orthosilicate (TEOS) oligomers and three cycloaliphatic polyesters. One series of polyester was synthesized using 1,4-cyclohexanedimethanol (CHDM) with 1,4-cyclohexanedicarboxylic acid (1,4-CHDA) and 1,3-cyclohexanedicarboxylic acid (1,3-CHDA). A second series of polyesters was synthesized using 2-butyl-2-ethyl-1,3-propanediol (BEPD) with 1,4-CHDA or 1,4-CHDA and 1,3-CHDA, respectively. The polyurethane provided the general mechanical properties and polysiloxane functioned as an adhesion promoter and a corrosion inhibitor. The continuous organic polyurethane phase was coupled to the inorganic polysiloxane phase via the alkoxysilane-functionalized HDI isocyanurate. The general coatings, tensile, and viscoelastic properties were evaluated for the ceramer coatings as functions of the polyester and concentration of TEOS oligomers. Damage tolerance was evaluated via fracture toughness and development of the film deformation zone prior to crack propagation. The coatings properties were dominated by the organic phase. The film morphology was investigated using the combination of SEM (Scanning Electron Microscope) and X-ray analysis. Phase separation was observed for ceramer coatings resulting in SiO 2 particles. The size of the pre-ceramic silicon-oxo-particles was controlled by the Tg of the organic phase and the concentration of TEOS oligomers.
Effect of Catalysts on the Model Reaction
of an Aliphatic Isocyanate with Water
Hai Ni, Heather A. Nash, James G. Worden and Mark D. Soucek* ¹
Polymers and Coatings Department, North Dakota State University, Fargo, ND 58105
Abstract
The kinetics of reaction of aliphatic isocyanate with water was investigated using hexyl isocyanate as a model compound. The kinetics study was carried-out using a titration method to determine the concentrations of the isocyanate group as a function of time. Gas chromatography (GC) was used to augment the kinetics data obtained from the titration method. The effect of an organic acid (p-toluene sulfonic acid monohydrate, p-TSA), a tertiary amine (diazabicyclo[2.2.2]octane, DABCO), and an organotin compound (dibutyltin dilaurate, DBTDL) on the reaction was investigated for the conversion of isocyanate to a urea. Under reaction conditions in this study, the urea was the only product observed. The rate constants indicated that p-TSA has low catalytic activity, DABCO has intermediate catalytic activity, and DBTDL has high catalytic activity. A reaction mechanism was proposed for each of the catalysts.
Cycloaliphatic Polyester Based High Solids
Polyurethane Coatings:
II. The Effect of Difunctional Acid
Hai Ni, Jeremy L. Daum, Pauline R. Thiltgen and Mark D. Soucek*
Polymers and Coatings Department, North Dakota State University, Fargo, ND 58105
William J. Simonsick Jr. and Wenqing Zhong
Abstract
Two series of polyesters were synthesized with isomeric cyclohexane diacids. The first series of polyesters was synthesized with 1,4-cyclohexanedimethanol (CHDM) and three cycloaliphatic difunctional acids, 1,4- cyclohexanedicarboxylic acid (1,4-CHDA), 1,3-cyclohexanedicarboxylic acid (1,3-CHDA), or hexahydrophthalic anhydride (HHPA). The second series was prepared with 1,4-CHDA and 1,3-CHDA with CHDM. Control polyesters with adipic, azelaic, and isophthalic acid (AA, AZA, IPA) were prepared for comparison. The solubility and viscosity of polyesters were investigated using the common solvent methyl ethyl ketone (MEK). All the polyesters were crosslinked with hexamethylene diisocyanate isocyanurate (HDI isocyanurate), forming polyurethane films. General coatings, tensile, and viscoelastic properties were evaluated for the cured polyurethane films. In addition, fracture toughness and the mode of energy dissipation were investigated. The polyesters based on cycloaliphatic diacids have better solubility in MEK compared to the polyesters based on the aromatic or linear aliphatic diacids. The cycloaliphatic diacids based polyurethane coatings had intermediate mechanical and viscoelastic properties compared to polyurethane based on aromatic and linear aliphatic diacids. In addition, the cycloaliphatic diacids afforded polyurethane with a greater adhesion on aluminum substrate compared to the aromatic diacid, IPA.
Polyurethane/Polysiloxane Ceramer Coatings:
Evaluation of Corrosion Protection
Hai Ni, Aaron H. Johnson and Mark D. Soucek* ¹
Polymers and Coatings Department, North Dakota State University
Fargo, ND 58105
John T. Grant and Andrew J . Vreugdenhil
Research Institute, University of Dayton, 300 College Park Dayton, OH 45469
Abstract
A series of polyurea and polyurethane ceramer coatings were formulated using hexamethylene diisocyanate (HDI) isocyanurate, alkoxysilane-functionalized HDI isocyanurate, tetraethyl orthosilicate (TEOS) oligomers and cycloaliphatic polyesters. The coatings were prepared as a function of alkoxysilane-functionalized HDI isocyanurate and TEOS oligomers concentration. Also, the effect of acid catalyst was investigated. The corrosion resistance of polyurea or polyurethane ceramer coating systems were evaluated using a prohesion chamber on aluminum alloy 2024-T3 substrate. The polyurethane ceramer coatings were compared with the chromate pretreatment and the epoxy-polyamide primer containing the chromate pigment. In addition to prohesion, the interface between the coating and substrate was characterized using X-ray photoelectron spectroscopy (XPS). The prohesion data showed that the corrosion was inhibited by the TEOS oligomers. However, high concentrations of TEOS oligomers and acid catalyst produced blistering in the polyurea/polysiloxane ceramer coatings. The prohesion data also showed that the corrosion protection of ceramer coatings perform just as well to the chromate pretreatment and competitively to the epoxy primer. From the XPS and prohesion data, a self assembling silicon oxide layer at the metal-coating interface was proposed
Cycloaliphatic Polyester Based High Solids
Polyurethane Coatings:
I. The Effect of Difunctional Alcohols
Hai Ni, Jeremy L. Daum, and Mark D. Soucek*
Polymers and Coatings Department, North Dakota State University, Fargo, ND 58105
William J. Simonsick Jr.
DuPont Marshall Research and Development Laboratory, 3401 Grays Ferry Avenue Philadelphia, PA 19146
Abstract
High solids polyesters were synthesized with two cycloaliphatic diacids, 1,4- cyclohexanedicarboxylic acid (1,4-CHDA) and 1,3-cyclohexanedicarboxylic acid (1,3-CHDA); and with five diols, 1,4-cyclohexanedimethanol (CHDM), neopentyl glycol (NPG), hydroxypivalyl hydroxypivalate (HPHP), 2-butyl-2-ethyl-1, 3-propanediol (BEPD), and 1,6-hexanediol (HD). The viscosity of the polyesters was dependent on the structures of diols. The viscosity of polyesters is lower with the diol HD, intermediate with BEPD and HPHP, and higher with the diols CHDM and NPG. The polyesters were crosslinked with hexamethylene diisocyanate isocyanurate (HDI isocyanurate) affording polyurethane coatings. The mechanical properties, tensile properties, fracture toughness, and viscoelastic properties were investigated for the polyurethane films with five different diols. The cyclohexyl structure of the CHDM provides the polyurethane with rigidity which is manifested in high tensile modulus, hardness, and fracture toughness. In contrast, the linear diol, 1,6-hexanediol provides polyurethane with very high flexibility, but these coatings suffer with respect to low hardness and tensile modulus.
Preparation and Characterization of Alkoxysilane Functionalized Isocyanurates
Hai Ni, † David J. Aaserud, ‡ William J. Simonsick jr, ‡ and Mark D. Soucek †*
† Polymers and Coatings Department, North Dakota State University, Fargo, ND 58105,
USA
‡ DuPont Marshall Research and Development Laboratory, 3401 Grays Ferry Avenue,
Philadelphia, PA 19146, USA
* To whom correspondence should be addressed.
Abstract
Alkoxysilane functionalized isocyanurates were prepared from HDI isocyanurate and 3-aminopropyltriethoxysilane. The reactants and functionalized isocyanurate were characterized by 1H, 13C and 29Si NMR, IR and electrospray ionization-mass spectrometry (ESI-MS). Two-dimensional NMR was necessary to accurately assign the proton and carbon spectra for both the reactants and functionalized products. The composition of the HDI isocyanurate was a mixture of oligomers ranging 2-8 HDI monomers. The functionalization reaction was performed neat, and as a function of dilution. As expected, substitution on the isocyanurate becomes more uniform with increasing solvent content.
Moisture-Curing Alkoxysilane-Functionalized Isocyanurate Coatings
Hai Ni, Allen D. Skaja, Robert A. Sailer and Mark D. Soucek *
Department of Polymers and Coatings, North Dakota State University, Fargo, ND 58105, USA
* To whom correspondence should be addressed.
Abstract
An aminosilane functionalized isocyanurate of 1, 6-hexamethylene diisocyanate (HDI isocyanurate) was used to formulate coatings. The coatings were formulated using a mixture of the silane-functionalized isocyanurate and the unfunctionalized HDI isocyanurate. The general coating properties and tensile properties were evaluated as a function of alkoxysilane modified isocyanurate. In addition, the thermo-mechanical and rheological properties of the films were also investigated. The moisture-curing process was investigated using FT-IR and NMR. The results indicated that alkoxysilane-functionalized isocyanurate dramatically enhanced the adhesion and increased the crosslink density.
Polyurea/Polysiloxane Ceramer Coatings
Hai Ni, † William J. Simonsick Jr, ‡ Allen D. Skaja,
Jonathan P. Williams and Mark D. Soucek †*
† Polymers and Coatings Department, North Dakota State University, Fargo, ND 58105,
USA
‡ DuPont Marshall Research and Development Laboratory, 3401 Grays Ferry Avenue,
Philadelphia, PA 19146, USA
Abstract
Tetraethylorthosilicate (TEOS) oligomers were prepared through the hydrolysis and condensation of TEOS with water. The mixture of TEOS oligomers was characterized by FT-IR, 29Si NMR and Electrospray Ionization-Mass Spectrometry (ESI-MS). The ESI-MS and 29Si NMR data show molecular weight ranges from 400-2000 g/mole and many cyclic species exist in addition to linear oligomers. The mechanical and tensile properties were evaluated as functions of TEOS oligomer concentration and silane-functionalized isocyanurate concentration. In addition, viscoelastic properties, thermal properties and morphology of the ceramer coatings were investigated using Dynamical Mechanical Thermal Analysis (DMTA), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM) with Energy Dispersion X-ray Analysis (EDAX). The data showed that ceramer coating properties were affected by both TEOS oligomer content and silane-functionalized isocyanurate content. Also, the adhesion was enhanced by incorporating the TEOS oligomers into the polyurea/polysiloxane coatings.
Acid-Catalyzed Moisture-Curing
Polyurea/Polysiloxane Hybrid Coatings
Hai Ni, Allen D. Skaja and Mark D. Soucek*
Department of Polymers and Coatings
North Dakota State University
Fargo, ND 58105, USA
Abstract
An alkoxysilane functionalized isocyanurate was prepared from 1, 6-hexamethylene diisocyanate isocyanurate (HDI isocyanurate) and 3-aminopropyltriethoxysilane. Tetraethylorthosilicate (TEOS) oligomers were prepared from TEOS, water and hydrochloric acid as a catalyst. Hybrid coatings were formulated using a mixture of the alkoxysilane-functionalized isocyanurate, unfunctionalized HDI isocyanurate, and tetraethylorthosilicate (TEOS) oligomers. The general coating properties and tensile properties were evaluated as a function of acid catalyst concentration. In addition, the effect of catalyst on coating films was investigated using differential scanning calorimeter (DSC) and dynamical mechanical thermal analyzer (DMTA). The results indicated that acid catalyst enhanced the adhesion of the hybrid coatings. The degree of crystallinity was decreased by addition of the acid catalyst. The addition of an acid catalyst also increased the crosslink density of films.