Coatings & Polymeric Materials Doctoral Work

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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.
Surface Modifying Amphiphilic Additives for the Improvement of Fouling-Release Properties of Siloxane-Polyurethane Coatings
(North Dakota State University, 2022) Benda, Jackson
Since mankind has navigated the world’s oceans, marine biofouling has been a persistent problem with several negative economic and environmental consequences. In modern times, the buildup of biofouling causes a significant reduction in vessel speed, leading to increased power consumption, higher costs of operation, and an increase in greenhouse gas emissions. Two of the most widely used protection strategies to combat this highly complex and dynamic phenomenon include the application of biocide containing anti-fouling (AF), or more environmentally friendly non-toxic fouling-release (FR) coatings. Traditional FR coatings utilize low surface energy components such as polydimethylsiloxane (PDMS), but often suffer mechanical failure and poor adhesion to the substrate. Recently, the development of a self-stratifying siloxane-polyurethane (SiPU) FR coating combined the desirable FR properties of PDMS containing materials, with the mechanically durable and tough attributes of a polyurethane. Several methods to improve on the FR properties of these coating systems involved the incorporation of hydrophilic moieties like polyethylene glycol (PEG), zwitterionic polymers, or carboxylic acid containing groups into the SiPU network, producing a heterogenous, amphiphilic surface. These types of amphiphilic surfaces have great potential to become a major component of the next generation of highly performing FR coatings. In this work, the use of non-reactive surface modifying amphiphilic additives (SMAAs) consisting of PDMS and PEG was explored as a viable method for further improvement of FR properties of SiPU coatings, while also maintaining coating integrity in marine environments. Additives with varying amounts of PDMS and PEG content were incorporated at several concentrations in both hydrophobic, and inherently amphiphilic SiPU FR coating systems. It was shown that these additives significantly alter the surface properties and morphology, producing surfaces that improve AF/FR performance against several model marine fouling organisms. The methodologies used for these types of coatings were also applied to a non-FR, polyurethane coating. This allowed for a more fundamental investigation into how these SMAAs are distributed throughout a coating system, and how FR properties arise. Lastly, commonly used FR coatings, including SiPUs, were applied to oil boom fabrics to observe their effect on FR properties and cleanability.
Synthesis and Characterization of Novel Polyvinylether Polymers Produced Using Carbocationic Polymerization
(North Dakota State University, 2011) Alam, Samim
Using carbocationic polymerization, a series of novel polyvinylether polymers and copolymers were synthesized and characterized. A series of polysiloxane copolymers containing polymer grafts possessing Triclosan moieties (PTVE) were synthesized using living carbocationic polymerization followed by hydrosilylation and investigated for potential application as environmental friendly coatings to control biofouling on marine vessels and biomedical devices. Copolymers possessing a relatively low molecular weight polysiloxane backbone and relatively high PTVE content exhibited very high reductions in biofilm retention for S. epidermidis and moderate reductions for C. lytica and C. albicans. In the second example, a novel monoallyl-functional initiator that was capable of producing very fast initiation of the living carbocationic polymerization of chloroethyl vinyl ether was synthesized and characterized. The monoallyl-functional polymers were used to produce a series of block copolymers containing blocks of polyquaternary ammonium compounds and polydimethylsiloxane (PDMS-b-PCVE-b-PQ) using hydrosilylation followed by quaternization with an n-alkyldimethyl amine. The PDMS-bPCVE-b-PQ copolymers in solution showed very high antimicrobial activity toward E. coli and S. aureus when the n-alkyl chains attached to the nitrogens of the quaternary ammonium compounds are consisted of 12 - 14 carbons and 14 - 16 carbons, respectively. In the third example, a novel, highly brominated polymer was synthesized from pentabromo-6-ethoxybenzene vinyl ether (BrVE) using cationic polymerization. The thermal and rheological properties of the polyBrVE (PBrVE) were compared to a commercially available oligomeric brominated flame retardant, poly(pentabromobenzyl acrylate) (PBrBA). In addition, polymer blends based on polybutylene terephthalate (PBT) were prepared with the two brominated polymers and the thermal stability, mechanical, and rheological properties compared. The use of PBrVE resulted in lower melt viscosity and better compatibility in blends with PBT which would be expected to provide enhanced processability with regard to creating injection molded parts with relatively thin walls, such as those encountered in the electronics industry. Finally, a process was developed to obtain vinyl ether-functional monomers containing fatty acid pendent groups directly from soybean oil (SBO) using base-catalyzed transesterification. Moreover, a carbocationic polymerization process was developed for the vinyl ether monomers that allowed for high molecular weight polymers to be produced. Compared to SBO, which possesses on average 4.5 vinyl groups per molecule, the polyvinylethers based on the soybean oil-derived vinyl ether monomers (polyVESFA) can possess tens to hundredss of vinyl groups per molecule depending on the polymer molecular weight produced. As a result of this difference, coatings based on polyVESF A were shown to possess much higher crosslink density at a given degree of functional group conversion compared to analogs based on conventional SBO. In addition, the dramatically higher number of functional groups per molecule associated with polyVESF A results in gel-points being reached at much lower functional group conversion, which was shown to dramatically reduce cure-time compared to SBO based analogs.
Sustainable Thermosetting Polymers: Biobased Epoxy Resin Systems and Aqueous Non-Isocyanate Polyurethanes
(North Dakota State University, 2022) Setien, Raul
In recent years, there has been a desire to seek alternatives to petrochemically derived materials. These alternatives can be derived from renewable sources such as vegetable oils. However, methods for achieving sustainability are not limited to only resourcing materials from bio-based sources but can also be achieved by utilizing safer synthesis techniques, reducing cure times, and eliminating volatile organic content in thermoset coating formulations. This dissertation sets out to achieve a goal the sustainability across different fields. Epoxidized sucrose soyate is a versatile bio-based materials that is typically synthesized utilizing hydrogen peroxide and acetic acid. A proposed safer alternative utilizes Oxone to generate dimethyldioxirane intermediates at room temperature to achieve the epoxidation of unsaturated sites in sucrose soyate and other vegetable oils such as soybean oil and hempseed oil. Thermosets made from epoxidized bio-based sources synthesized from dimethyldioxirane intermediates or in-situ generated peracids showed little to no difference in thermal and coatings properties. The use of epoxidized sucrose soyate with reactive diluents in cationic photopolymerization was also explored. The thermal characterizations of the thermoset coatings created utilizing this method indicate that crosslinking had not occurred to completion. In an effort to reduce the use of volatile organic content the feasibility of utilizing cyclic carbonates and primary carbamates in water borne polyurethane systems was explored. It was found that utilizing cyclic carbonates with higher ring strain, such as 6-membered cyclic carbonates, provides a potential way for creating non-isocyanate crosslinking thermoset coatings from waterborne polyurethane dispersions.
Modification of Diglycidyl Ether of Bisphenol-A Epoxy Primer for Multi-Substrate Application
(North Dakota State University, 2022) Chea, Gwendorlene
Traditional vehicles and aircraft have consisted primarily of steel and aluminum alloys which due to their density, has resulted in various logistic problems including transportation, maneuverability, fuel efficiency. These hindrances have led to a major increase in the incorporation of composites material into this equipment. As the use of these composite increases, multi-substrate coating systems that can provide adequate corrosion protection to metal components, as well as superior adhesion and flexibility to the composites, are needed. The goal of this work is the modification of diglycidyl ether of bisphenol-A epoxy coating systems for improved flexibility and adhesion for the development of multi-substrate primer. For this purpose, commercial additives of various chemistry (liquid rubber, polysulfide, novolac phenolic resins, silane coupling agents, and polyethers) were incorporated into a model epoxy-polyamine coating and their effect on flexibility and adhesion was investigated. Based on their performance, the top-performing additives were incorporated into a fully pigmented modified primer. Overall, the studies in this dissertation not only demonstrated improved flexibility and adhesion to metal and composites but also improved overall corrosion protection compared to an unmodified primer.
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.
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.
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.
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.
Soysomes and Other Functional Biomaterials from Sucrose Soyate Derivatives
(North Dakota State University, 2019) Wright, Ruvimbo Pearl
Biomaterials serve as interventional tools in medicine to treat, improve or replace diseased tissues, organs or function of the body. Although several polymeric biomaterials already exist, they often present challenges, at material level, such as non-biodegradability, degradation into acidic by-products or tissue incompatibility, or at functional level such as failure to sustain prolonged release of therapeutic payload for a desired period. Research has been focused on investigating new polymeric candidates to address these problems of current systems. The use of renewable resources to generate smart polymers for biomedical and pharmaceutical purposes presents a new and exciting avenue for biomaterials. As part of these efforts, a new set of biomaterials were developed from plant-derived high molecular weight (~3.0 kDa) compounds. The advantages of biobased materials include availability for large-scale synthesis, facile post-synthetic modification, biocompatibility, improvement of functional properties and affordability. In this project we used sucrose soyates, i.e. octa-esters obtained from conjugation of sucrose molecules and multiple soybean oil fatty acid chains, to prepare three groups of functional biomaterials namely: a). self-assembled soy-based nano-constructs, b). blended soy-based free-standing films and c). three-dimensional cross-linked soy-based soft matrices. Here, we will discuss the fabrication and physical, chemical and mechanical characterization of these biomaterials prepared from soy-based compounds, as well as, the assessment of their functional performance in biological environment.
Novel Biobased Resins using Sucrose Esters of Plant Oils
(North Dakota State University, 2011) Pan, Xiao
Interest in using renewable raw materials to prepare biobased monomers, polymers, and materials is rapidly increasing. The goal of the research described is to develop branched polyesters of plant oil fatty acids, using different core pol yo ls (i.e. sucrose, dipentaerythritol, and tripentaerythritol) and plant oils (i.e. linseed, safflower, and soybean), into curing systems that have potential uses in applications such as coatings, composites, and adhesives. This study is mainly focused on the use of sucrose as the core polyol in the soyate resins. Sucrose esters and their derivatives have a compact structure, high density, and high functionality-double bonds, epoxides, or hydroxyls. When considering the use of sucrose ester compounds to form cross linked materials, the rigid core of sucrose can potentially impart hardness to the thermoset, and the high functionality can lead to rapid gelation and high cross link density. Thus, these novel biobased resins using sucrose esters of plant oils have the potential to be a significant advance in biobased resin technology, as well as to be competitive with the conventional petroleum-based resins.
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.
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.
Siloxane-Polyurethane Fouling-Release Coatings Based On PDMS Macromers
(North Dakota State University, 2011) Sommer, Stacy Ann
Marine biofouling is the accumulation of organisms onto surfaces immersed in sea water. Fouling of ships causes an increase in hydrodynamic drag which leads to performance issues such as increased fuel consumption and a reduced top operating speed. Fouling-release (FR) coatings are one way that paints have been used in combating biofouling by allowing for the easy removal of settled organisms. Traditional FR coatings are silicone elastomers which are soft, easily damaged, and require a tie coat for adhesion to marine primers. Siloxanepolyurethane FR coatings have shown promise as FR coatings, providing enhanced durability and toughness, better adhesion to marine primers, and comparable FR performance to commercial coatings. Preliminary studies were conducted to explore the use of PDMS macromers in the preparation of siloxane-polyurethane FR coatings. Attachment and removal of fouling organisms on the siloxane-polyurethane coatings based on PDMS macromers was comparable to commercial FR coatings. Extended water aging was also carried out to determine effects of extended water immersion on the fouling-release performance of the coatings. At up to four weeks of aging, the FR performance of the coatings was not affected. Static immersion marine field testing was performed to determine the fouling-release performance of siloxane-polyurethane coatings prepared with PDMS macromers. The performance was found to be comparable to commercial FR coatings for up to one year, including water jet removal of slimes, barnacle push-off removal, and soft sponging. The coatings showed good fouling-release performance until extremely heavy fouling was allowed to settle. Underwater hull cleaning was conducted for one siloxane-polyurethane composition identified as a top performer from static field testing. The coating was easily cleaned of fouling with rotating brushes for six months. The cleaning capability of the coating was reduced when large barnacles and other extremely heavy fouling was present. A commercial FR coating became heavily damaged with brush cleaning while the siloxane-polyurethane coating remained mostly undamaged. With more frequent cleaning, it is suspected that siloxanepolyurethane coatings would show cleaning capability for longer periods of time. Pigmentation of siloxane-polyurethane coatings based on difunctional PDMS and PDMS macromers was explored to investigate the effect on FR performance. Pigmentation with titanium dioxide caused a slight decrease in FR performance in some cases, but this was easily overcome by the addition of slightly more PDMS in the coating binder, thus illustrating the feasibility of siloxane-polyurethane coatings as effective, pigmented FR coatings. Finally, the exploration of unique PDMS polymer architectures has been explored for the development of additional, novel, fouling-release coatings. The incorporation of end-functional PDMS homopolymer molecular brushes and branched PDMS macromers into siloxane-polyurethane fouling-release coatings shows promise for the development of unique coatings where improved FR performance may be obtained.
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.
Surface Optimization of Siloxane-Polyurethane Marine Coatings for Improved Fouling-Release Properties
(North Dakota State University, 2016) Galhenage, Teluka Pasan
Biofouling has been an economically and environmentally costly problem to mankind ever since they set sail. Biofouling causes frictional drag leading to slow vessel speeds, and increased fuel costs. Antifouling (AF) coatings containing biocides have been used for decades, however, since some biocides have shown undesired effects towards the environment, a non-toxic solution to combat fouling is desired. Subsequently, fouling release (FR) coatings quickly gained acceptance as a non-toxic approach to contend with biofouling. Unlike AF coatings, FR coatings not necessarily prevent settlement of organisms, they permit weak adhesion which is easily released by water shear or light grooming. The siloxane-polyurethane (SiPU) coatings based on the concept of self-stratification is a non-toxic and durable approach to prepare FR coatings. In this work, several approaches were considered to optimize surface properties of SiPU coatings. Incorporation of phenyl-methyl silicone oils led to improved FR properties towards several marine organisms in laboratory assays and in ocean field immersion. Enhancement in FR properties may be attributed to slowly exuding silicone oil providing surface lubricity, weakening the adhesion of marine organisms. Addition of diphenyldimethyl siloxane in to SiPU coatings at different ratios resulted in micro-scale surface topographical features which negatively affected microfouling-release while several coatings displayed good FR performance towards macrofouling organisms. In another study, decreasing the acid group content helped to improve FR performance towards barnacles, but FR performance towards diatoms were compromised. Novel amphiphilic siloxane-polyurethane (AmSiPU) coatings from polyisocyanate pre-polymers modified with polydimethyl siloxane and polyethylene glycol displayed excellent FR properties towards several marine organisms during laboratory assays. These AmSiPU coatings show promise as contenders to commercial FR standards. Initial development of SiPU coatings with hydrophilic surfaces showed promise, as the coatings showed rapidly rearranging surfaces with comparable FR performance to commercial standards which claim hydrophilic surface properties. During freshwater field immersion trials, SiPU coatings displayed excellent mussel FR performance up to 3 years. Surface analysis suggested that solvent content affected self-stratification and morphology of SiPU coatings. The SiPU coating system is a highly tunable, tough, environmentally friendly, and practical FR solution which can evolve along with non-toxic commercial marine 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.
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.
Magnesium Alloy Particulates Used as Pigments in Metal-Rich Primer System for AA2024 T3 Corrosion Protection
(North Dakota State University, 2010) 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 A1 alloys (in particular A1 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, A719B, 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 alter 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, A2918 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 alter exposure were identiﬁed. It was found that variation of A1 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.
Magnesium Rich Primer for the Corrosion Protection of Aluminum Alloys: Investigation, Improvement and Application
(North Dakota State University, 2016) Lin, Junren
The goals of this research are to develop deeper understanding of the corrosion protection mechanism of Mg-rich primer (MgRPs), improve corrosion protection performance of MgRPs, and extend the application of MgRPs. To address these research goals, the following studies were performed: 1. Early blistering problems encountered during constant immersion or ASTM B117 exposure of top-coated MgRPs over AA2024-T3 substrate were investigated. The results suggest that hydrogen entrapment by topcoat, instead of Al corrosion, contributes significantly to the formation of early blistering. Meanwhile, simultaneous real-time hydrogen collection and open circuit potential measurement was demonstrated as a new method for studying the corrosion protection mechanism of MgRPs. Moreover, the gas generated from MgRPs was unequivocally identified as hydrogen by cyclic voltammetry. 2. Degradation behaviors of MgRP in 1% NaCl solution and Dilute Harrison Solution (DHS) were compared through scanning electron microscopy, hydrogen volume collection and electrochemical tests. The effects of connection modes between Mg pigment and Al substrate, different ions on the formation and stability of Mg oxidation products, and cathodic reaction sites on the microstructure of MgRP were discussed. In addition, an in situ method for the estimation of remaining Mg pigment in MgRP was developed based on H2 volume collection. 3. The effects of adding sodium benzoate (SB), sodium dodecylbenzenesulfonate (SDBS), and 8-hydroxyquinoline (HQ) to MgRP on its corrosion protection of AA 2024-T3 were investigated. The results show that addition of SB, SDBS and HQ into MgRP improved the corrosion protection performance of MgRP by decelerating the oxidation rate of Mg, improving coating barrier properties and inhibiting the corrosion of Al alloy substrate. 4. The (MgRP-powder topcoat) coating system was developed and characterized in this research for the corrosion protection of Al alloys. The results show that powder topcoat can be applied on top of MgRP through both fluidized bed and electrostatic spray methods. Moreover, this (MgRP-powder topcoat) coating system provided much longer corrosion protection time to Al substrate than the powder coat by itself, without degrading other coating properties.

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