Coatings & Polymeric Materials Doctoral Work

Permanent URI for this collectionhdl:10365/32413

Browse

Now showing 1 - 20 of 40

Surface Property Modification of Coatings via Self-Stratification
(North Dakota State University, 2010) Pieper, Robert Joseph
Biological fouling occurs everywhere in the marine environment and is a significant problem for marine vessels. Anti-fouling coatings have been used effectively to prevent fouling; however, these coatings harm non-targeted sea-life. Fouling-release coatings (FRC) appear to be an alternative way to combat fouling. FRC do not necessarily prevent the settlement of marine organisms but rather allow their easy removal with application of shear to the coatings surface. These coatings must be non-toxic, non-leaching, have low surface energy, low modulus, and durability to provide easy removal of marine organisms. Here the goal is to develop FRC based on thermosetting siloxane-polyurethane, amphiphilic polyurethane, and zwitterionic/amphiphilic polyurethane systems. A combinatorial high-throughput approach has been taken in order to explore the variables that may affect the performance of the final coatings. Libraries of acrylic polyols were synthesized using combinatorial high-throughput techniques by either batch or semi-batch processes. The design of the experiments for the batch and semi-batch processes were done combinatorially to explore a range of compositions and various reaction process variables that cannot be accomplished or are not suitable for single reaction experiments. Characterization of Rapid-GPC, high-throughput DSC, and gravimetrically calculated percent solids verified the effects of different reaction conditions on the MW, glass transition temperatures, and percent conversion of the different compositions of acrylic polyols. Coatings were characterized for their surface energy, pseudobarnacle pull-off adhesion, and were subjected to bioassays including marine bacteria, algae, and barnacles. From the performance properties results the acrylic polyol containing 20% hydroxyethyl acrylate and 80% butyl acrylate was selected for further siloxane-polyurethane formulations and were subjected to the same physical, mechanical, and performance testing. Amiphiphilic copolymers based on PDMS molecular weight and the addition of PEG based polymer blocks on the properties of acrylic-polyurethane coatings were explored. The key properties screened were surface energy, determined by contact angle measurements using water and methylene iodide, dynamic water contact angle, and pseudobarnacle adhesion properties. The data from all of the biological assays indicates that the novel coatings were able to resist fouling and have low fouling adhesion for the broad variety of fouling organisms tested.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Novel Hybrid Polymeric Materials for Barrier Coatings
(North Dakota State University, 2012) Pavlacky, Erin
Polymer-clay nanocomposites, described as the inclusion of nanometer-sized layered silicates into polymeric materials, have been widely researched due to significant enhancements in material properties with the incorporation of small levels of filler (1 - 5 wt.%) compared to conventional micro- and macro-composites (20 - 30 wt.%). One of the most promising applications for polymer-clay nanocomposites is in the field of barrier coatings. The development of UV-curable polymer-clay nanocomposite barrier coatings was explored by employing a novel in situ preparation technique. Unsaturated polyesters were synthesized in the presence of organomodified clays by in situ intercalative polymerization to create highly dispersed clays in a precursor resin. The resulting clay-containing polyesters were crosslinked via UV-irradiation using donor-acceptor chemistry to create polymer-clay nanocomposites which exhibited significantly enhanced barrier properties compared to alternative clay dispersion techniques. The impact of the quaternary alkylammonium organic modifiers, used to increase compatibility between the inorganic clay and organic polymer, was studied to explore influence of the organic modifier structure on the nanocomposite material properties. By incorporating just the organic modifiers, no layered silicates, into the polyester resins, reductions in film mechanical and thermal properties were observed, a strong indicator of film plasticization. An alternative in situ preparation method was explored to further increase the dispersion of organomodified clay within the precursor polyester resins. In stark contrast to traditional in situ polymerization methods, a novel "reverse" in situ preparation method was developed, where unmodified montmorillonite clay was added during polyesterification to a reaction mixture containing the alkylammonium organic modifier. The resulting nanocomposite films exhibited reduced water vapor permeability and increased mechanical properties. The novel preparation of hybrid films coupling the advantageous properties of organic-inorganic hybrids formed through sol-gel chemistry with polymer-clay nanocomposite technology was also explored. Alkoxysilane-functional copolymer-clay nanocomposites were first synthesized, followed by crosslinking via simultaneous hydrolysis and condensation reactions to create the novel hybrid barrier films. By dispersing organomodified clay throughout the hybrid network, dramatic improvements in several film properties were observed, particularly regarding the viscoelastic properties. Additional studies with the same organic-inorganic preparation technique were performed to incorporate amine-functionality into the hybrid film for potential applications as protective membranes in carbon dioxide capture and separation technologies. Finally, controlled free-radical polymerization techniques were combined with the preparation of the organic-inorganic hybrids.
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.
Silicon-Based Hybrid Organic-Inorganic Polymers and Coatings
(North Dakota State University, 2012) Bao, Hanzhen
Interest in producing hybrid organic-inorganic (HOI) materials has increased rapidly due to the unique combination of properties from the organic and inorganic components. The goal of the research described is to develop various HOI materials and explore their applications in corrosion protection over aerospace aluminum alloys, impact resistant materials, and surface protection over thermoplastic substrates. As a replacement to toxic chromate inhibitors, enrivonmentally friendly magnesium-rich primers (Mg-rich primers) have been investigated to provide corrosion protection over aerospace aluminum alloys. HOI binders were produced from an alkoxy silane and silica via sol-gel chemistry, where the combined organic and inorganic components provide flexibility, adhesion, and barrier properties. The derived topcoated Mg-rich primers showed promising corrosion protection in a salt spray exposure test and are competitive with chromate-containing primers. The condensation catalyst, tetrabutyl ammonium fluoride (TBAF), played an important role in the performance of the HOI binders and the derived Mg-rich primers. It enabled higher crosslink density and better barrier properties, however, reacted with Mg particles during salt spray exposure and caused the formation of blisters. A non-ionic condensation catalyst, dibutyltin dilaurate (DBTDL), had lower catalyst strength, but was expected to eliminate the blister formation of topcoated Mg-rich primers. Perfectly alternating polycarbonate-polydimethylsiloxane (PC-PDMS) multiblock copolymers were produced to create transparent impact resistant materials by confining the size of the rubber domains. The PC-PDMS block copolymers maintained high transparency at up to 62 wt% PDMS and shorter block length gave rise to larger partial miscibility. By incorporating the PDMS blocks to dissipate energy, the PC-PDMS block copolymers had much better impact strength than pure PC oligomers. Thermoset polycarbonate-polyhedral oligomeric silsesquioxane (PC-POSS) coatings were investigated to serve as surface coatings on PC substrate to provide abrasion resistance. The covalent bonding allowed high POSS loading at up to 18 wt% without sacrificing the transparency. The solvent composition and curing conditions largely determined the surface and bulk properties of the coatings. The incorporation of POSS molecules significantly increased the char yield and mechanical strength of the thermoset coatings, making them promising in surface protection applications.
Novel Conducting Polymer Containing Composite Coatings for the Corrosion Protection of Metal Alloys
(North Dakota State University, 2013) Jadhav, Niteen
Corrosion is a persistent problem faced by manmade structures made up of metal alloys. Aluminum 2024-T3 is high strength, light weight alloy used in aerospace applications. It suffers from the problem of corrosion due to its composition. Cold rolled steel is employed in structural applications but undergoes severe corrosion when exposed to corrosive conditions. Coatings are one of the best avenues to protect metal alloys from the corrosion. Traditional coating systems such as barrier type coatings, metal rich coatings, and inhibitor containing coatings have their own drawbacks. Conducting polymers (CPs), such as polypyrrole (PPy) can be used for the corrosion protection of the metals. Redox activity in conjunction with corrosion inhibiting ion release ability make CPs as a promising candidate for the replacement for hexavalent chromates. However CPs porous nature, inherent insolubility, stiff chains, and poor mechanical properties pose significant hindrance towards their implementation in coatings. In order to overcome the problems associated with the CPs and to extract maximum functionality out of them, conducting polymer containing composites (CPCC) were developed. CPCC combines CPs with inorganic pigments in unique ways and pave for excellent properties. In this work, series of composites of PPy/Inorganic pigments (aluminum flakes, iron oxide, micaceous iron oxide, and titanium dioxide) were synthesized by ecofriendly, facile chemical oxidative polymerization. Core and shell morphologies of PPy with titanium dioxide and iron oxide were synthesized and employed for the corrosion protection of cold rolled steel substrate. Various dopants such as phosphate, nitrate, molybdate, vanadate, and tungstate were incorporated in the backbone of PPy. These composites were characterized for morphology, elemental composition, and conductivity by various techniques. Furthermore coatings based on these composite pigments were formulated on Aluminum 2024-T3 and cold rolled steel substrates. These coatings were exposed to salt spray and prohesion test conditions and electrochemically evaluated against corrosion by Electrochemical Impedance Spectroscopy (EIS), DC Polarization, galvanic coupling and Scanning Vibrating Electrode Technique (SVET). Effect of solvent in the composite synthesis and PPy morphology in the final composite on the protective properties of coating was investigated. Effect of corrosion inhibiting anions on the final performance properties was also evaluated.
Organic Coatings to Protect Ferrous Structures
(North Dakota State University, 2013) Huang, Yaping
Corrosion induces damages that can result in enormous costs and safety issues. Steels are the most commonly used metallic structural materials but they can corrode rapidly when exposed to corrosive environments and need to be protected. The thesis research focuses on two aspects of steel protection. The first aspect is using barrier protection mechanism to protect steel pipeline structures in the presence of Super-Critical CO2. The second aspect is improving cathodic protection of steels by metal rich coatings in ground vehicles, bridges, water tanks, and other structures. In part one, coatings for protection of steel pipeline used for carbon transportation in the form of supercritical carbon dioxide were examined. Pipeline coatings serve to protect pipelines by maintaining their integrity and to increase their service time. Different pipeline coatings with the exposure to SCCO2 have been examined, and these results will be presented here. Different parameters, such as the thickness of coatings, the exposure temperature and pressure, and the exposure time as they affect pipeline coating were investigated and will be described. In the second part of this thesis research, the addition of magnesium particles to the standard zinc particles as metal rich primer was examined for the improvement of current zinc rich coatings to serve as protection for metal substrates in Army ground vehicles. Optimization of primer formulation, such as ratio of Mg and Zn, was investigated. The test primers were exposed in accelerated weathering tests, including ASTM B117 salt spray method and ProhesionTM cycle test as part of this research. The results have been compared with the behavior of the current commercial zinc rich primers to identify the improvements in the protection of the steel with mixed metal systems. For both investigations, electrochemical impedance spectroscopy was mainly used to examine coating performance. Other tests, including color measurement, thickness measurement, X-ray diffraction measurements, and pH measurements, were used to examine the corrosion behavior of steel structures under different corrosive environments. Results showed that coating systems can protect ferrous structures in ways of barrier protection and cathodic protection and can be improved by the application of modern methods and equipment.
Multiscale Modeling of Electromagnetic Radiation Transport
(North Dakota State University, 2013) Sapper, Erik David
The transport of electromagnetic radiation is a critical factor in determining many of the advanced features of novel materials, composites, and coatings systems. The radiation interaction with a material's surface, as well as its transport and interaction within the material, both combine to produce the overall electromagnetic signature of that object, which is the root cause of the color and appearance of these materials. Historically, approaches to light scattering behavior prediction focus on either the surface interactions or the bulk interactions, and the models most used today are valid only for certain compatible size and length scales of radiation. As next generation materials become more advanced, and increasingly have formulation components that reside on the nanoscale, a robust, rigorous, yet highly general approach to electromagnetic signature prediction is required. A hybrid, multiscale approach to the computational prediction of light scattering by coatings and composite materials is presented here, where ray tracing and geometric optics formalism tracks individual photons as they enter the material of interest, and finite element solutions to the Maxwell equations are used to generate the radiation interaction result of nanoscale inclusions embedded within the bulk of the material. The approach presented here is highly general in nature; scattering inclusions may be pigments, fibers, nanoparticles, air voids, or heterogeneous phase components. The multiscale approach enables investigation of the electromagnetic signature at various length scales, and predicts spectral reflectance, directional reflectance, and color, among other properties, of various multicomponent systems.
Responsive Polymer-Based Colliods for Drug Delivery and Bioconversion
(North Dakota State University, 2014) Kudina, Olena
Responsive polymer-based colloids (RPBC) are the colloidal structures containing responsive polymeric component which is able to adapt its physico-chemical properties to the environment by undergoing chemical and/or conformational changes. The goal of the dissertation is to develop and characterize several groups of RPBC with different morphological complexity and explore their potential in drug delivery and bioconversion. The role of RPBC morphology for these specific applications is discussed in details. Three groups of RPBC were fabricated: i. polymeric micelles; ii. mixed polymeric micelles; iii. hybrid polymer-inorganic particles. All fabricated RPBCs contain polymeric component in their structure. The dissertation investigates how the changes of the responsive polymeric component properties are reflected in morphologies of RPBC. The first group of RPBC, polymeric micelles, was formed by the self-assembly of amphiphilic invertible polymers (AIPs) synthesized in our group. AIPs self-assemble into invertible micellar assemblies (IMAs) in solvents of different polarity. In this work, IMAs ability to invert the structure as a response to the change in solvent polarity was demonstrated using 1H NMR spectroscopy and SANS. It was shown that the IMAs incorporate hydrophobic cargo either in the core or in the shell, depending on the chemical structure of cargo molecules. Following in vitro study demonstrates that loaded with drug (curcumin) IMAs are cytotoxic to osteosarcoma cells. Mixed polymeric micelles represent another, more complex, RPBC morphologies studied in the dissertation. Mixed micelles were fabricated from AIPs and amphiphilic oligomers synthesized from pyromellitic dianhydride, polyethylene glycol methyl ethers, and iv alkanols/cholesterol. The combination of selected AIP and oligomers based on cholesterol results in mixed micelles with an increased drug-loading capacity (from 10% w/w loaded curcumin in single component IMAs to 26%w/w in mixed micelles). Even more complex colloids are hybrid polymer-inorganic particles, the third RPBC group studied in dissertation. Material was designed as core–shell particles with superparamagnetic core engulfed by grafted polymer brushes. These particles were loaded with enzymes (cellulases), thus, are turned into enzymogels for cellulose bioconversion. The study demonstrates that such RPBCs can be used multiple times during hydrolysis and provide an about four-fold increase in glucose production in comparison to free enzymes.
pH Responsive Capsules Containing Composite Coatings for Corrosion Inhibition in Metal Alloys
(North Dakota State University, 2014) Kashi, Kiran Bhat
Hexavalent chromes have be used as effective corrosion inhibitors due to their high inhibitor efficiency and low cost for the protection of several metal alloys. However, owing to their toxicity federal legislations restrict the use and distribution of these highly toxic materials. The need for an environmentally friendly yet effective alternative to the chrome based corrosion inhibitors has led to the investigation of rare earth metals as potential candidates. Cerium is one such rare earth metal that has received considerable attention as an alternative to hexavalent chromes. However, the high water solubility of some of the cerium salts makes it difficult for the incorporation of such salts in coatings. In this work, pH responsive microcapsules containing cerium salts were synthesized using an internally phase separated emulsion polymerization technique. Core shell microcapsule consisting of a water core containing dissolved cerium salts were synthesized. The synthesized capsules were characterized using characterization techniques such as Fourier Transform Infrared (FTIR) spectroscopy, UV-vis spectroscopy, Dynamic Mechanical Analysis (DMA), Thermo-Gravimetric Analysis (TGA), and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The structure and morphology of the capsules were studied using electron microscopy techniques. The synthesized capsules were dispersed in 2K epoxy coatings and applied on aluminum alloy 2024 T-3 and cold rolled steel substrates. These coatings were exposed to salt spray (ASTM B117) and electrochemically evaluated using electrochemical impedance spectroscopy (EIS), potentio-dynamic(PD) polarization, cyclic voltammetry(CV), open circuit potential(OCP) measurements. Localized corrosion assessment was also performed on the coated metal alloys using Scanning electrochemical microscopy (SECM) to understand the mechanism of corrosion inhibition using cerium encapsulated microcapsules.
Synthesis, Characterization, and Applications of Electroactive Polymeric Nanostructures for Organic Coatings
(North Dakota State University, 2015) Suryawanshi, Abhijit Jagnnath
Electroactive polymers (EAP) such as polypyrrole (PPy) and polyaniline (PANI) are being explored intensively in the scientific community. Nanostructures of EAPs have low dimensions and high surface area enabling them to be considered for various useful applications. These applications are in several fields including corrosion inhibition, capacitors, artificial muscles, solar cells, polymer light emitting diodes, and energy storage devices. Nanostructures of EAPs have been synthesized in different morphologies such as nanowires, nanorods, nanotubes, nanospheres, and nanocapsules. This variety in morphology is traditionally achieved using soft templates, such as surfactant micelles, or hard templates, such as anodized aluminum oxide (AAO). Templates provide stability and groundwork from which the polymer can grow, but the templates add undesirable expense to the process and can change the properties of the nanoparticles by integrating its own properties. In this study a template free method is introduced to synthesize EAP nanostructures of PPy and PANI utilizing ozone oxidation. The simple techniques involve ozone exposure to the monomer solution to produce aqueous dispersions of EAP nanostructures. The synthesized nanostructures exhibit uniform morphology, low particle size distribution, and stability against agglomeration. Ozone oxidation is further explored for the synthesis of silver-PPy (Ag-PPy) core-shell nanospheres (CSNs). Coatings containing PPy nanospheres were formulated to study the corrosion inhibition efficiency of PPy nanospheres. Investigation of the coatings using electrochemical techniques revealed that the PPy nanospheres may provide corrosion inhibition against filiform corrosion by oxygen scavenging mechanism. Finally, organic corrosion inhibitors were incorporated in PPy to develop efficient corrosion inhibiting systems, by using the synergistic effects from PPy and organic corrosion inhibitors.

Browse

Browsing Coatings & Polymeric Materials Doctoral Work by Issue Date