Browsing by Subject "coatings"
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Item Multiply Complex, Non-Toxic, Anti-Fouling Surfaces Designed for Marine and Biomedical Applications(2014-12-09) Pollack, Kevin ABiofouling, the undesired accumulation of biological organisms on a surface, is a problem that plagues a wide spectrum of materials. Because of the ban of heavy metal paint formulations, there has been a rapid movement towards the development of novel anti-biofouling coatings based upon various polymeric networks. The main focus of this dissertation is to design and develop unique polymeric networks that display unique heterogeneities in regards to topography, topology and chemical composition on the micro- and nano-scales that can be explored as non-toxic coatings for the deterrence of organisms in the marine environment. These materials also have potential to serve as anti-biofouling coatings for biomedical and other applications. A two dimensional array of terpolymer networks based on the crosslinking of hyperbranched fluoropolymers (HBFP) with varying concentrations of poly(ethylene glycol) (PEG) and polydimethylsiloxane (PDMS) were generated. Crosslinking coincides with and is followed by degrees of thermodynamically-driven phase separation within the bound network and results in a complex surface that displays dynamically-reorganizing heterogeneity in its topography, topology and chemical composition on both the nano- and the micro-scales. The coatings were characterized using atomic force microscopy (AFM), surface force spectroscopy, and static water contact angle to probe their surface properties. Because of the performance displayed in anti-biofouling testing for the terpolymer networks, a more industrially-relevant method for applying the networks was sought. Through the use of a spray coating application method, the terpolymer network could be laid down onto a Naval-approved epoxy barrier coating. The epoxy barrier coating provides functional handles to covalently bond the terpolymer network to the substrate without further modification. The coatings were then tested, through collaborations with the University of Newcastle, Florida Institute of Technology, the University of Hawaii at Manoa and California Polytechnic State University against various marine organisms and in static water immersion testing to test their viability as anti-biofouling coatings. Additionally, the ability to expand the concept the of the terpolymer networks was investigated. These studies included the use of different components for each of the three components of the system. Specifically, the use of silsesquioxanes as a hydrophobic component, zwitterions as a hydrophilic component and a bis-functional fluorinated molecule was explored using AFM, IR, static water contact angle and an anti-biofouling study against Ulva zoospores. In summary, both systems studied displayed potential as next-generation anti-biofouling coatings.Item Quantitative characterization of polymer scratch behavior using a standardized scratch test(Texas A&M University, 2007-09-17) Browning, Robert LeeThe lack of a widely-accepted quantitative methodology for evaluating the scratch behavior of polymeric materials has resulted in the development and establishment of a new methodology recently standardized as ASTM D7027-05. Using a custom-built instrumented scratch machine, it is possible to produce controlled, repeatable scratches on polymer surfaces under constant or linearly increasing loading conditions at constant or increasing scratch rates. Software-aided digital image analysis along with material science tools (SEM, OM, FTIR, etc.) allows polymer scratch behavior to be analyzed without the ambiguity inherent in the past. The current work will serve to describe the motivation for the development of this methodology as well as illustrate the effectiveness of the increasing load/constant rate test mode in three case studies. First, it will be shown that an acrylic coating on a steel system exhibits three zones of scratch damage: adhesive delamination, transverse cracking and finally buckling failure. It will be discussed how increases in ductility and thickness serve to improve the scratch resistantance of this coating/substrate system. Improvements in the scratch behavior of thermoplastic olefins (TPOs) through the use of surface-treated talc fillers and the slip agent erucamide will be shown in the second case. It was found that the surface-treatment of the talc likely allows for enhanced migration of the erucamide to the TPO surface, thus lowering the surface friction and greatly increasing scratch resistance. Finally, the effects of processing conditions, namely injection molding, on the scratch behavior of neat i-polypropylene will be represented by the results of scratch tests conducted where the scratch direction was oriented both along and transverse to the polymer melt flow direction. Based on the findings of the study, there appears to be a high degree of surface anisotropy introduced to injection-molded polymers due to complex fluid flow regimes as well as non-uniform cooling properties.Item Role of relative humidity in concrete expansion due to alkali-silica reaction and delayed ettringite formation: relative humidity thresholds, measurement methods, and coatings to mitigate expansion(2009-05) Rust, Charles Karissa; Folliard, Kevin J.; Juenger, Maria C. G.Premature concrete deterioration due to alkali-silica reaction (ASR) and delayed ettringite formation (DEF) is a significant problem all over the world. In cases where these mechanisms were not initially prevented, mitigation is critical to halt expansion and cracking. The main objectives of the research presented herein were to study the effect of ambient relative humidity (RH) on rates of concrete expansion, to determine RH thresholds below which expansion due to ASR and/or DEF may be suppressed, and to evaluate coatings intended to lower the internal RH of concrete and thus minimize future potential for damage. Results from testing showed that the RH threshold for ASR was below 82%, the RH threshold for DEF was below 92%, and the RH threshold for combined ASR and DEF could be about 83% for the materials tested. Furthermore, it was shown that some coatings are effective in reducing ASR- and DEF-related expansion by lowering the internal RH of concrete.