Coatings & Polymeric Materials Doctoral Work

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Advanced Electrochemical Methods for Characterizing the Performance of Organic Coatings
(North Dakota State University, 2012) Upadhyay, Vinod
Advanced electrochemical techniques such as electrochemical impedance spectroscopy (EIS), electrochemical noise method (ENM) and coulometry as tools to study and extract information about the coating system is the focus of this thesis. This thesis explored three areas of research. In all the three research areas, advanced electrochemical techniques were used to extract information and understand the coating system. The first area was to use EIS and coulometric technique for extracting information using AC-DC-AC method. It was examined whether the total charge passing through the coating during the DC polarization step of AC-DC-AC determines coating failure. An almost constant total amount of charge transfer was required by the coating before it failed and was independent of the applied DC polarization. The second area focused in this thesis was to investigate if embedded sensors in coatings are sensitive enough to monitor changes in environmental conditions and to locate defects in coatings by electrochemical means. Influence of topcoat on embedded sensor performance was also studied. It was observed that the embedded sensors can distinguish varying environmental conditions and locate defects in coatings. Topcoat could influence measurements made using embedded sensors and the choice of topcoat could be very important in the successful use of embedded sensors. The third area of research of this thesis work was to examine systematically polymer-structure coating property relationships using electrochemical impedance spectroscopy. It was observed that the polymer modifications could alter the electrochemical properties of the coating films. Moreover, it was also observed that by cyclic wet-dry capacitance measurement using aqueous electrolyte and ionic liquid, ranking of the stability of organic polymer films could be performed.
Amphiphilic Invertible Polymers: Self-Assembly into Functional Materials Driven by Environment Polarity
(North Dakota State University, 2012) Hevus, Ivan
Stimuli-responsive polymers adapt to environmental changes by adjusting their chain conformation in a fast and reversible way. Responsive polymeric materials have already found use in electronics, coatings industry, personal care, and bio-related areas. The current work aims at the development of novel responsive functional polymeric materials by manipulating environment-dependent self-assembly of a new class of responsive macromolecules strategically designed in this study, – amphiphilic invertible polymers (AIPs). Environment-dependent micellization and self-assembly of three different synthesized AIP types based on poly(ethylene glycol) as a hydrophilic fragment and varying hydrophobic constituents was demonstrated in polar and nonpolar solvents, as well as on the surfaces and interfaces. With increasing concentration, AIP micelles self-assemble into invertible micellar assemblies composed of hydrophilic and hydrophobic domains. Polarity-responsive properties of AIPs make invertible micellar assemblies functional in polar and nonpolar media including at interfaces. Thus, invertible micellar assemblies solubilize poorly soluble substances in their interior in polar and nonpolar solvents. In a polar aqueous medium, a novel stimuli-responsive mechanism of drug release based on response of AIP-based drug delivery system to polarity change upon contact with the target cell has been established using invertible micellar assemblies loaded with curcumin, a phytochemical drug. In a nonpolar medium, invertible micellar assemblies were applied simultaneously as nanoreactors and stabilizers for size-controlled synthesis of silver nanoparticles stable in both polar and nonpolar media. The developed amphiphilic nanosilver was subsequently used as seeds to promote anisotropic growth of CdSe semiconductor nanoparticles that have potential in different applications ranging from physics to medicine. Amphiphilic invertible polymers were shown to adsorb on the surface of silica nanoparticles strongly differing in polarity. AIP modified silica nanoparticles are able to adsolubilize molecules of poorly water-soluble 2-naphthol into the adsorbed polymer layer. The adsolubilization ability of adsorbed invertible macromolecules makes AIP-modified silica nanoparticles potentially useful in wastewater treatment or biomedical applications. Finally, the invertible micellar assemblies were used as functional additives to improve the appearance of electrospun silicon wires based on cyclohexasilane, a liquid silicon precursor. AIP-assisted fabrication of silicon wires from the liquid cyclohexasilane precursor has potential as a scalable method for developing electronic functional materials.
Design of Polymer Materials with Lower Environmental Impact
(North Dakota State University, 2015) Popadyuk, Andriy
In today’s world of emerging advanced materials, environmental impact of new technologies, as well as already well-established products, is of utmost importance. Environmental safety is as crucial as performance/price ratio for new materials. Talking specifically about polymer materials, research efforts are dedicated to enhancing material biodegradability, sustainability, manufacturing process improvements etc. It starts to become an industrial standard – to eliminate solvents from polymer production routines, reduce number of chemicals, increase biobased content and generally move towards “green synthesis” concept (use of renewable and/or reclaimed resources throughout whole production process). The main goal of this work was to develop novel polymers and polymer materials to have potentially lower environmental impact, including new biobased polymer materials with properties and performance not sacrificed by the presence of renewable content, and demonstrate the feasibility of new polymers in industrial applications. For the purpose of achieving the goal of this work, several approaches were attempted. The first approach lies in the development of a new polymer - poly[n-(tert-butylperoxymethyl) acrylamide-co-maleic anhydride], which combines the features of both initiator and surfactant (the inisurf), to be applied in conventional emulsion polymerization. Use of the inisurf allows for synthesis of novel, in-situ functionalized (peroxidized) latex particles, while reducing the number of chemicals involved in the process. Another focus of this work was on the development of biobased polymer materials, from plant oils as a raw source, which would be used to substitute petroleum-based polymers. For this, soybean based polymer surfactants (amphiphylic copolymers) were synthesized, and their potential to be applied as surfactant ingredients in shampoos was evaluated. In addition, synthesis of novel biobased monomers from sebacic (castor oil) and caprylic (coconut, palm oils) fatty acids – dipropylene glycol acrylate caprylate and dipropylene glycol diacrylate sebacate is presented. Both monomers are shown to be applicable for development of thermosensitive latex particles for controlled encapsulation and release of fragrance in cosmetic products. Finally, a synthetic route for the fabrication of new soybean oil based acrylic monomer for free radical polymerization for making latexes for paints and adhesives is disclosed.
Development of Novel Kraft Lignin Resin for Use in Thermoset Materials
(North Dakota State University, 2019) Krall, Eric
Video summarizing a Ph.D. dissertation for a non-specialist audience.
The Effect of Fatty Acid Unsaturation on Properties and Performance of Monomers and Latex Polymers from Plant Oils
(North Dakota State University, 2020) Demchuk, Zoriana
The interest in renewable natural resources, including plant oils, has become increasingly appealing due to the oil abundance, availability, and wide range of applications for polymers and polymeric materials thereof. In this dissertation, a library of plant oil-based acrylic monomers (POBMs) with a broad range of unsaturation was synthesized using a one-step transesterification. It is demonstrated that the unsaturation degree of plant oil remains preserved during the synthesis and determines the structure and properties of POBMs. The life cycle assessment (LCA) was conducted in this study to evaluate the environmental impact of soybean oil-based acrylic monomer (SBM) production. LCA was applied to provide guidance for SBM synthesis optimization, including the type of catalyst, the ratio between reactants, renewable sources (soybean oil/biodiesel), and solvent recycling. The performed LCA shows the positive effect of the inclusion of the solvent recycling step in the SBM synthesis. This study shows that POBMs behave as conventional vinyl monomers in free radical polymerization and copolymerization. The monomer unsaturation impacts polymerization rate and molecular weight of resulted polymers decreasing as follows: poly(OVM) > poly(SFM) > poly(SBM) > poly(LSM), due allylic termination presented during polymerization. A series of stable POBM-based latexes with high solid content (40-45 %) and monomer conversion (95-97 %) were synthesized using miniemulsion process. The incorporation of POBMs fragments provides the plasticizing effect on the resulting latex polymers, as seen by a noticeable decrease in their glass transition temperature (Tg). The crosslink density of POBM-based latex films follows the linear dependence vs. monomer feed unsaturation, providing a tool for controlling latex mechanical properties, including hardness, toughness, Young's modulus, etc. Besides, the presence of highly hydrophobic POBM fragments enhances water resistivity of latex coatings and films. Following the "greener" vector of research, a variety of stable latexes from high oleic soybean oil-based monomer (HOSBM) and cardanol, eugenol, and guaiacol derivatives were synthesized in miniemulsion. Resulting polymeric materials advantageously combine flexibility provided by HOSBM fragments with strength facilitated by aromatic biobased units.
Electrically Conductive Polymers and their Use as Novel Pigments in Advanced Coatings
(North Dakota State University, 2018) Byrom, Joseph Robert
With the push to more environmentally friendly materials to solve some of the biggest challenges in the coatings industry, electrically conductive polymers (ECPs) are seen as a flexible solution due to their unique properties. ECPs are seen as an attractive substitute to the current metallic materials used in applications such as printable electronics, anti-static protection, and corrosion mitigation. Polypyrrole (PPy) is seen as a popular class of ECPs due to its inherent high electrical conductivity, resistance to environmental degradation, and ease of synthesis. The first part of this work was to study the ability of polypyrrole to be synthesized through a novel photochemical process. This method eliminated the need to stabilize particles in a suspension and deposit an electrically conductive film onto a variety of substrates. The second part of this work was to synthesize functional versions of PPy that could further be crosslinked into the coating matrix to improve bulk physical properties through better interaction between the functional filler and the organic coating matrix. The last part of this work is based off prior work at NDSU on AL-flake/PPy composites. This study took the development of these pigments further by incorporating organic anions known to inhibit corrosion and study their efficacy. Advanced analytical methods such as Conductive Atomic Force Microscopy was used to study the electrical properties of PPy. In addition, advanced electrochemical tests such as Electrical Impedance Spectroscopy (EIS), Scanning Vibrating Electrode Technique (SVET), Linear Polarization (LP), and Galvanic Coupling (GP) were conducted alongside traditional accelerated weathering techniques such as ASTM B117 and GM 9540 to determine the corrosion resistance of the synthesized coatings.
Embedded Reference Electrodes for Corrosion Potential Monitoring, Electrochemical Characterization, and Controlled-Potential Cathodic Protection
(North Dakota State University, 2012) Merten, Bobbi Jo Elizabeth
A thin wire Ag/AgCl reference electrode was prepared using 50 μm Ag wire in dilute FeCl3. The wire was embedded beneath the polyurethane topcoat of two sacrificial coating systems to monitor their corrosion potential. This is the first report of a reference electrode embedded between organic coating layers to monitor substrate health. The embedded reference electrode (ERE) successfully monitored the corrosion potential of Mg primer on AA 2024-T3 for 800 days of constant immersion in dilute Harrison’s solution. Zn primer on steel had low accuracy in comparison. This is in part due to short circuiting by Zn oxidation products, which are much more conductive than Mg corrosion products. Data interpretation was improved through statistical analysis. On average, ERE corrosion potentials are 0.1 to 0.2 V and 0.2 to 0.3 V more positive than a saturated calomel electrode (SCE) in solution for AA 2024-T3 and steel coating systems, respectively. Further research may confirm that ERE obtains corrosion potential information not possible by an exterior, conventional reference electrode. The ERE is stable under polarization. AA 2024-T3 was polarized to -0.95 V vs ERE to emulate controlled potential cathodic protection (CPCP) applications. Polarizations of -0.75 V vs ERE are recommended for future experiments to minimize cathodic delamination. The ERE was utilized to analyze coating mixtures of lithium carbonate, magnesium nitrate, and Mg metal on AA2024-T3. Corrosion potential, low frequency impedance by electrochemical impedance spectroscopy (EIS), and noise resistance by electrochemical noise method (ENM) were reported. Coating performance ranking is consistent with standard electrochemical characterization and visual analyses. The results suggest anti-corrosion resistance superior to a standard Mg primer following 1600 hours of B117 salt spray. Both lithium carbonate and magnesium nitrate are necessary to achieve corrosion protection. Unique corrosion protective coatings for aluminum could be designed through continued mixture optimization. The Ag wire ERE has been utilized for the characterization and ranking of experimental coatings on metal substrates. Structural health monitoring and corrosion potential feedback of cathodic protection systems are additional uses. There is some indication that CPCP may be applied by ERE to control the substrate polarization for an organic coating system.
Epoxidized Sucrose Soyate and Derivatives as Bioderived Crosslinkers in Various Thermosets
(North Dakota State University, 2019) Silbert, Samantha Danielle
Throughout the world, alternatives to petrochemically-derived materials are being sought. Aside from petrochemical feedstocks with precarious futures, materials that are derived from renewable resources such as crops are attractive. Epoxidized sucrose soyate is a material made from soybean oil and sucrose. Its rigid sucrose core, flexible aliphatic chains, and many modifiable epoxy sites make it an attractive candidate to replace petrochemically derived materials in a multitude of thermosets. This dissertation encompasses studies of ESS and its derivatives for the development of thermosets in a variety of processes. Namely, ESS-derived polycarbamates for use in ambient-curing polyurethane coatings produced via carbamate-dialdehyde crosslinking, ESS-derived acrylic resins for their use in stereolithographic printing, and UV-curable epoxy coatings from both ESS and adhesion-promoting derivatives. The incorporation and effect of strengthening and/or processing additives were also assessed in the mentioned ESS-containing thermosets. Each topic involves a unique area where formulations use resins derived from petrochemicals; several posing health and/or environmental concerns. Investigations to match or exceed the performances of conventional formulations with alternatives made with ESS further demonstrate the remarkable tunability and versatility of this material, as well as the assets available to lessen reliance on petrochemicals with the use of a renewable resource.
Features of Highly Hydrophobic Plant Oil-Based Vinyl Monomers in Cationic and Free Radical Polymerization
(North Dakota State University, 2019) Kingsley, Kyle
The demand for polymeric materials, which have traditionally been produced from petroleum-based resources over the last century, continues to grow each year. However, the supply of fossil fuels is limited. This, along with price volatility, harmful effects on the environment, and stricter regulations, have led to a surge in the exploration of suitable replacements, namely renewable resources such as plant and vegetable oils. In this work, newly synthesized highly hydrophobic plant oil-based vinyl monomers were polymerized using different mechanisms and processes to obtain polymer coatings and crosslinked films. First, novel vinyl ether monomers derived from soybean oil were copolymerized with vinyl ether counterparts derived from poly(ethylene glycol) (PEG) via cationic polymerization to prepare alkyd-type coatings. Soybean oil-derived polymer coatings and free films were formed by autoxidation of the unsaturation provided by the parent soybean oil moieties. Studies revealed that mechanical and viscoelastic properties, hydrophobicity, and morphology of coatings were dependent on copolymer composition and even more strongly on molecular weight and molecular weight distribution. The soybean oil-derived polymer coatings exhibited Tg values below room temperature, and it was shown that their thermomechanical properties were dependent on crosslink density. Next, plant oil-based acrylic monomers (POBMs) from soybean, high oleic soybean, and olive oils were copolymerized with styrene, methyl (meth)acrylate, and vinyl acetate to yield latexes and prepare polymer films with tailorable thermomechanical properties. Feasibility of the emulsion process was realized with regard to parent plant oil structure (unsaturation amount), POBM content and comonomer aqueous solubility, by determining copolymerization kinetics, mode(s) of latex particle nucleation, and molecular weight of resulting latex copolymers. POBM-emulsifier interactions, competing modes of latex particle nucleation, and effect of comonomer radical reactivity have all been investigated. Total monomer conversion and molecular weight of latex copolymers were enhanced by incorporation of an amphiphilic oligosaccharide (methyl-β-cyclodextrin) within the reaction system, which increases the availability of the POBMs and simultaneously diminishes degradative chain transfer reactions that are triggered by POBM fatty acid unsaturation fragments.
Fouling Release Marine Coatings: Effect of Surface Abrasions on Fouling Release Performance of Self-Stratified Siloxane-Polyurethane Coatings and Novel Isocyanate-Free Glycidyl Carbamate Technologies
(North Dakota State University, 2017) Pade, Madhura
Video summarizing a Ph.D. dissertation for a non-specialist audience.
Functional Colloids from Amphiphilic Polymer Assemblies and Peptides/Polypeptides
(North Dakota State University, 2019) Zholobko, Oksana
The use of responsive polymers, where even minor changes in one of the macromolecular characteristics triggered by the external stimuli can cause drastic changes in the material function or performance, is widely studying area of research. Formation of the thermodynamically stable polymer-peptide colloids, such as mixed micellar assemblies or polymer-enzyme conjugates, loading capacity of the colloids, and cargo activity all depend on the macromolecular interactions within the peptide/polypeptide-polymer system. The goal of this work is to investigate interactions between range of new polymers and various cargo molecules and determine whether those interactions affect the physicochemical properties of the resulted colloids. For this purpose, two types of colloid systems were explored: i) peptide-loaded invertible micellar assemblies (IMAs), formed using hydrophobic interactions between amphiphilic invertible polymers (AIP) and peptides (HA, V5, or peptide-based vaccine), and ii) polymeric cellulosomes made from polymer ligand (PL), copolymer of glycidyl methacrylate (GMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) and mixture of cellulases, using covalent bonding. The purpose of the research was to evaluate if colloids properties are affected by changes in responsive polymer characteristics as well as if the developed macromolecular structure and composition need further synthetic modification/optimization. AIP-related part of this dissertation is focused on i) understanding of interaction between peptides and AIPs, and formation of mixed micellar assemblies; ii) further behavior of cargo peptide molecules in the micellar interior under the AIP conformational changes, triggered by IMAs localization at polar and nonpolar interface; iii) evaluation of the impact of IMAs on model lipid membrane diffusivity and permeability. Besides, AIP-peptide assemblies were tested in vitro and in vivo in order to evaluate the cargo delivery, antibody response, and immunity protection in vaccinated pigs against Swine influenza viruses (SIV). To explore the feasibility of covalent bonding in formation of responsive polymer-based colloids, enzyme-polymer conjugates (EPCs) were designed and their enzymatic catalytic activity for the biomass hydrolysis was further tested. The effect of conjugation on catalytic activity, conjugation efficiency, glucose inhibition effect, type of substrate, and type of biomass pretreatment were evaluated and compared to free enzymes.
High Performance Bio-Based Thermosets for Composites and Coatings
(North Dakota State University, 2016) Ambeg Paramarta, Adlina
In the recent decade, there has been increasing interest in using renewable feedstocks as chemical commodities for composites and coatings application. Vegetable oils are promising renewable resources due to their wide availability with affordable cost. In fact, the utilization of vegetable oils to produce composite and coatings products has been around for centuries; linseed oil was widely used for wide variety of paints. However, due to its chemical structure, the application of vegetable oils for high-performance materials is limited; and thus chemical modification is necessary. One of the modification approaches is by substituting the glycerol core in the triglycerides with sucrose to form sucrose esters of vegetable oil fatty acids, in which this resin possesses a higher number of functional group per molecule and a more rigid core. In this research, thermosets of highly functionalized sucrose esters of vegetable oils were developed. Two crosslinking methods of epoxidized surcrose soyate (ESS) resins were explored: direct polymerization with anhydride moieties for composite applications and Michael-addition reaction of acrylated-epoxidized sucrose soyate (AESS) for coatings applications. In the first project, it was shown that the reaction kinetics, thermal and mechanical properties of the materials can be tuned by varying the molar ratio between the epoxide and anhydride, plus the type and amount of catalyst. Furthermore, the toughness properties of the ESS-based thermosets can be improved by changing the type of anhydride crosslinkers and incorporating secondary phase rubbers. Then, in the second system, the epoxy functionality in the ESS was converted into acrylate group, which then crosslinked with amine groups through the Michael-addition reaction to produce coatings systems. The high number of functional groups and the fast reactivity of the crosslinker results in coatings that can be cured at ambient temperature, yet still possess moderately high glass transition temperatures.
High-Throughput Methods for Characterizing the Mechanical Properties of Coatings
(North Dakota State University, 2012) Siripirom, Chavanin
The characterization of mechanical properties in a combinatorial and high-throughput workflow has been a bottleneck that reduced the speed of the materials development process. High-throughput characterization of the mechanical properties was applied in this research in order to reduce the amount of sample handling and to accelerate the output. A puncture tester was designed and built to evaluate the toughness of materials using an innovative template design coupled with automation. The test is in the form of a circular free-film indentation. A single template contains 12 samples which are tested in a rapid serial approach. Next, the operational principles of a novel parallel dynamic mechanical-thermal analysis instrument were analyzed in detail for potential sources of errors. The test uses a model of a circular bilayer fixed-edge plate deformation. A total of 96 samples can be analyzed simultaneously which provides a tremendous increase in efficiency compared with a conventional dynamic test. The modulus values determined by the system had considerable variation. The errors were observed and improvements to the system were made. A finite element analysis was used to analyze the accuracy given by the closed-form solution with respect to testing geometries, such as thicknesses of the samples. A good control of the thickness of the sample was proven to be crucial to the accuracy and precision of the output. Then, the attempt to correlate the high-throughput experiments and conventional coating testing methods was made. Automated nanoindentation in dynamic mode was found to provide information on the near-surface modulus and could potentially correlate with the pendulum hardness test using the loss tangent component. Lastly, surface characterization of stratified siloxane-polyurethane coatings was carried out with X-ray photoelectron spectroscopy, Rutherford backscattering spectroscopy, transmission electron microscopy, and nanoindentation. The siloxane component segregates to the surface during curing. The distribution of siloxane as a function of thickness into the sample showed differences depending on the formulation parameters. The coatings which had higher siloxane content near the surface were those coatings found to perform well in field tests.
Highly Functionalized Thermosets from Renewables for Composites and Coatings Applications
(North Dakota State University, 2017) Yu, Arvin
Renewable sources have attracted attention due to their affordable cost and wide availability. Vegetable oils are renewable sources that have been extensively studied as potential replacement for petroleum derived chemicals. However, vegetable oils tend to produce soft materials with modest properties due to their chemical structure. Consequently, their modifications have been studied to develop high performance materials with improved properties. One of the modifications involves substituting the glycerol core with sucrose to increase the functionality per molecule. Another approach is converting the less reactive internal carbon-carbon double bonds with the more reactive epoxy groups, which permits access to a variety of crosslinking pathways. Epoxidized sucrose soyate (ESS) is a sucrose ester fatty acid (SEFA), which was epoxidized via the Prilezhaev reaction. ESS has a rigid sucrose core and epoxy functionalized fatty acid side chains. The high functionality of ESS was exploited and it was converted to methacrylated and carbonated resins. The methacrylated resins were applied in producing themosets by free-radical polymerizations while the carbonated resins were studied in step-growth polymerizations. Several studies were done to exploit the high functionality of the methacrylated resins: reduction of the viscosity while increasing crosslinkable moieties, introduction of ductility, structure-property relationships, and investigation of resin versatility in photocurable systems. Meanwhile, the carbonated resins were used to form non-isocyanate polyurethane (NIPU) coatings via cyclic carbonate-amine reactions. Overall, the highly functionalized bio-based thermosets showed very promising properties for composites and coatings applications.
Improving Sustainability in Protective Coating Systems
(North Dakota State University, 2019) Rohly, Alison Marie
Sustainability has been a driving factor in the recent development of protective coating systems, from reducing volatile organic compounds (VOC’s), integrating biomass for the replacement of petrochemicals, to reducing the number of synthetic or processing steps within a coating system. Incorporating changes to established technologies requires research initiatives focused on matching or exceeding performance properties while maintaining or lowering costs. As a result, sustainable changes to protective coating systems have been under heavy investigation as market demands shift from petrochemicals to renewable materials. This research focuses on the development of unique thermoset coating systems and sustainable improvements. The first study explores the hydrolytic stability between a silanol and an isocyanate, a frequently used reaction that has been relatively understudied. Incorporation of potential hydrolytically unstable silyl carbamates into polyurethane systems may decrease the crosslinking efficiency of the overall network, negatively impacting coating performance. As a result, investigation into the stability of silyl-carbamates may prevent further inefficiencies by eliminating use of this chemistry within polyurethane systems. The second study focuses on the development of alkoxysilane sol-gel consolidants for the protection of stone materials. Sustainable approaches to consolidant formulation include the reduction and elimination of solvent while improving consolidating properties through material selection. The last two studies focus on the incorporation of lignin-derived vanillin into epoxy thermosets and melamine formaldehydes, increasing the overall biobased content of each system.
Influence of Surface Topography and Curing Chemistry on Fouling-Release Performance of Self-Stratified Siloxane-Polyurethane Coatings
(North Dakota State University, 2017) Pade, Madhura
Biofouling, the attachment and growth of microorganisms and aquatic animals on submerged surfaces, poses many economic and environmental challenges like increase in frictional drag, fuel consumption, and cost of maintenance of ships. Coatings containing harmful biocides, called anti-fouling (AF) coatings, are used to combat fouling. But, the biocides proved toxic to the aquatic environment, which led to replacement of AF coatings by non-toxic fouling-release (FR) coatings. FR coatings do not contain toxic biocides and allow formation of a weak bond between the surface and the organisms, which can be easily broken through light grooming or hydrodynamic forces. Current research is aimed at developing robust coatings that can exhibit similar or superior FR performance as compared to commercial FR coatings. Previously, self-stratified FR coating systems were developed using siloxane and polyurethane (SiPU) in the Webster research group. Although the SiPU coatings exhibited comparable FR performance to the commercial standards, previous experiments did not show effect of surface grooming or cleaning on the FR performance. In the first part of the work, an SiPU formulation was abraded using two different Scotch Brite pads with varying roughness. Surface analysis experiments showed retention of hydrophobicity even after abrasions. The abraded coatings were characterized for FR performance against common fouling organisms. Improvement in FR performance of the abraded coatings compared to the smooth SiPU coating and the commercial standards against macrofoulants, like barnacles, was attributed to dimensions of the features formed on the coatings after abrasions. Recent concerns regarding hazards associated with using isocyanates to make polyurethanes necessitated the need to find “safer” alternatives in FR marine applications. Therefore, novel isocyanatefree glycidyl carbamate (GC) technologies were explored as potential substitutes for regular polyurethanes to make FR marine coatings. GC resins were modified using siloxanes and polyethylene glycols to make hydrophobic and amphiphilic coatings with varying surface chemistries. The resultant coatings were characterized for mechanical properties, thermal behavior, and finally, FR performance against common fouling organisms. Although GC coatings showed subpar overall FR performance as compared to the commercial standards, GC technologies show potential for use in marine applications.
Interaction of Tackifier Resins with Water-based and Olefinic Polymers
(North Dakota State University, 2012) Rajesh Raja, Puthenkovilakom
The objective of this research was to investigate the interaction of tackifier resins in water-based and olefinic polymers for potential pressure sensitive adhesive applications. The first part of this research work was focused on evaluating the usefulness of olefinic block copolymer blends with two amorphous polyolefins (atactic propylene homopolymer and ethylene-propylene copolymer) as potential base polymers for hotmelt pressure-sensitive adhesives. Unsaturated and saturated hydrocarbon resins were studied as potential compatibilizing agents and rheology modifiers. Results show that the chemistry of hydrocarbon resins definitely influence the miscibility of the olefinic block polymer and amorphous polyolefin blends. Ethylene-propylene amorphous copolymer based blends seems to show better miscibility characteristics. Based on the learning from blend miscibility studies, we have successfully made pressure-sensitive adhesives for disposable diaper construction application with olefinic block copolymer/ethylene-propylene amorphous copolymer blends, containing unsaturated hydrocarbon resins and saturated hydrocarbon resins. These olefinic adhesives showed good sprayability characteristics, when applied using air assisted spiral spray equipment (Acumeter Spray Coater) and they showed good adhesive peel properties, which were comparable to the SBS based control. The second part of the study was focused on the evaluation of natural rubber latex-based pressure-sensitive adhesives (PSA) containing three different C5 aliphatic tackifier dispersions with different softening points. Natural rubber-based, water-borne PSA wet rheology (rheology in liquid state) was correlated to morphological analysis on a coating and converting stand point. Dry adhesive rheology was also studied and was then correlated to adhesive properties at different conditions. It has been learned that the type and amount of dispersing agents in tackifier dispersions has a major influence in wet rheology of the PSA formulations. Softening point of the dispersion seems to influence the dry adhesive rheology and adhesive properties such as peel, tack and shear.
Investigation of Novel Approaches for Improved Amphiphilic Fouling-Release Coatings
(North Dakota State University, 2020) Rahimi, Alireza
Marine biofouling has troubled mankind, both environmentally and economically, since they set sail, resulting in many undesired consequences such as increased drag, reduced maneuverability, increased fuel consumption and greenhouse gas emissions, and heightened maintenance costs. This problem is highly complex as it involves more than 4000 marine organisms with varying modes of adhesion and surface preferences as well as many aquatic environments. The common state-of-the-art approaches to contend with marine biofouling on the submerged surfaces of ships in seawater has antifouling (AF) and fouling-release (FR) surfaces. As AF coating systems utilize biocides which are often toxic to the environment to prevent settlement of biofoulants, the endeavors have been shifted towards non-toxic FR marine system. Many FR systems take advantage of low surface energy and modulus polydimethylsiloxane (PDMS) on their surface, while the recent attempts explored the simultaneous effect of PDMS and hydrophilic moieties (i.e. polyethylene glycol (PEG) or zwitterionic polymers) on an FR surface, known as amphiphilic surfaces. Thus, the work in this dissertation focused on attaining amphiphilic surfaces with desirable FR performance. The studies in this dissertation were investigated to deliver two goals: 1) Enhancing the (FR) fouling-release performance of previously developed coating systems; 2) Introducing novel fouling-release marine coatings with set criteria. To address the former, a series of amphiphilic additives containing PDMS and hydrophilic polymers (zwitterionic-based or PEG) were prepared in chapters two-five. These additives were incorporated in several previously developed FR coating systems in order to modify their surfaces and enhance their FR performance. To address the latter, two amphiphilic marine coating systems were explored for accessing durable, non-toxic, and effective FR surfaces using epoxy-amine crosslinking chemistry. Overall, the studies in this dissertation not only demonstrated viable FR surfaces with desirable performance against several representative marine organisms such as N. incerta, U. linza, C. lytica, barnacles, and mussels but also contributed a deeper understanding about the effect of amphiphilicity concentration/balance on surface and FR properties.
Low VOC Coating Systems From Novel Glycidyl Carbamate Resins
(North Dakota State University, 2010) Harkal, Umesh Deepak
The goal of the research presented in this dissertation was to design and synthesize novel glycidyl carbamate (GC) resins for low VOC applications and study the structure property relationships of their coatings. Primarily GC resins are synthesized using aliphatic polyisocyanate resins such as biuret and isocyanurate of hexamethylene diisocyanate. Polyisocyanate based GC resins had extremely high viscosity. Biuret glycidyl carbamate (BGC) resin was modified by replacing part of the glycidol with alcohols. The alcohol composition and the extent of alcohol composition in the resin were systematically varied. The alcohol modification reduced the resin viscosity dramatically. Performance of amine and self-crosslinked GC coatings was studied. GC resins were synthesized for binder systems for flexible primer applications using diisocyanates and combinations of linear diols and a triol. The diisocyanates, diols and triol were used to obtain GC resins. Flexibility and barrier properties of the amine crosslinked coatings were influenced by the composition of the GC resins. Water dispersible GC resins were synthesized for low or zero VOC waterborne coating applications. Non-ionic hydrophilic group, methoxy poly(ethylene glycol) (mPEG), was incorporated into the resin structure. Molecular weight and mol % of mPEG in the resin was systematically varied. Waterborne GC coatings were prepared using water-based amine crosslinker and properties of the cured coatings were studied. UV curable GC resins were made by reacting BGC, isocyanurate glycidyl carbamate (IGC), and alcohol modified IGC resins with acrylic acid. UV curable coating formulations were prepared using reactive diluents, a photoinitiator, and an amine coinitiator. Real-time FTIR (RTIR) was used to determine the degree of double bond conversion in UV curing. The performance of the UV cured coatings was studied. Finally, air drying (autoxidizable) GC resin (BGC-LOFA) was obtained by reacting BGC resin with linseed oil fatty acid (LOFA). Air drying GC coatings were obtained using common driers used for alkyd-based coatings.
Magnesium Alloy Particulates used as Pigments in Metal-Rich Primer System for AA2024 T3 Corrosion Protection
(North Dakota State University, 2011) Xu, Hong
As an alternative to the present toxic chromate-based coating system now in use, the Mg-rich primer technology has been designed to protect Al alloys (in particular Al 2024 T3) and developed in analogy to Zn-rich primers for steel substrate. As an expansion of this concept, metal-rich primer systems based on Mg alloy particles as pigments were studied. Five different Mg alloy pigments, AM60, AZ91B, LNR91, AM503 and AZG, were characterized by using the same epoxy-polyamide polymer as binder, a same dispersion additive and the same solvent. Different Mg alloy-rich primers were formulated by varying the Mg alloy particles and their pigment volume concentrations (PVC). The electrochemical performance of each Mg alloy-rich primer after the cyclic exposure in Prohesion chamber was investigated by electrochemical impedance Spectroscopy (EIS). The results indicated that all the Mg alloy-rich primers could provide cathodic protection for AA 2024 T3 substrates. However, the Mg alloys as pigments in metal-rich primers seemed to exhibit the different anti-corrosion protection performances, such as the barrier properties, due to the different properties of these pigments. In these investigations, multiple samples of each system were studied and statistical methods were used in analyzing the EIS data. From these results, the recommendation for improved EIS data analysis was made. CPVC studies were carried out on the Mg alloy-rich primers by using three Mg alloy pigments, AM60, AZ91B and LNR91. A modified model for predicting CPVC is proposed, and the results showed much better agreement between the CPVC values obtained from the experimental and mathematical methods. Using the data from the AM60 alloy pigment system, an estimate of experimental coarseness was done on a coating system, the first time such an estimate has been performed. By combining various surface analysis techniques, such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and confocal Raman microscopy, the oxidation products formed after exposure were identified. It was found that variation of Al content in Mg alloy could significantly affect the pH of the microenvironment in the primer films and result in the formation of various oxidation products.

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