The performance of three different lipid/hydrocolloid coatings was tested on Golden Delicious apples. The coatings consisted of a mixture of lipid, wax, and various gum blends. The three treatments were compared to an uncoated group (control). Both objective and sensory tests were performed to determine the shelf-life stability of the apples. Objective results indicated that all three treatments significantly decreased (P<0.0083) the respiration rates of the apples when compared to the control. The treatment groups also significantly (P<0.0083) maintained the texture of the apples along with a lower (P<0.0083) starch degradation rate. The treatment groups also significantly (P<0.0083) maintained the malic acid level in the apple. There were no significant differences (P>0.0083) among the groups with regard to soluble solids and fresh weight loss. Externally, the treated apples had a significantly greener hue (Hunter color "a") than the control apples, however, there were no significant differences (P>0.0083) in yellow color (Hunter color "b") between the groups. Sensory results indicated that the treated apples were firmer, crisper and juicier (P<0.0083) than the control apples. However there were no significant differences (P>0.0083) in the sweetness, tartness, and appearance of all of the groups. Overall, the derived coatings could serve as a resource for extending and maintaining the shelf life of perishable fruit. / Master of Science

The ultimate goal of this dissertation research is to enhance the protein resistant nature of poly(ethylene oxide) (PEO) or poly(ethylene glycol) by introduction of a siloxane linker and to subsequently prepare coatings which prevent surface-induced thrombosis. The hydrophobicity and flexibility of the siloxane tether should impart both amphiphilicity and conformational mobility to the PEO chain to further decrease protein adhesion. Because adsorption of plasma (blood) proteins initiates the clotting process, coating surfaces based on these new PEO-silanes should prevent or significantly diminish thrombosis. Thus, these coatings would be extremely useful for bloodcontacting medical devices such as stents, grafts, arteriorintravenous shunts, and biosensors. Novel amphiphilic PEO-silanes were prepared with systematic variations to several key structural features, including: siloxane tether length, PEO segment length, and PEO architecture. Thus, PEO-silanes were prepared having the general formulas: a-(EtO)3Si(CH2)2-oligodimethylsiloxanen-block-[PEO8-OCH3] (n = 0, 4, and 13; linear architecture) and a-(EtO)3Si(CH2)2-oligodimethylsiloxanen-block-[PEOm-OCH3]2 (n = 0, 4, and 13; m = 6 and 12 branched architecture). The reactive triethoxysilane [(EtO)3Si-] group serves as the crosslinking or grafting moiety. The PEO segment is distanced from the (EtO)3Si- group by an oligodimethylsiloxane tether which is both hydrophobic and exhibits a high degree of chain flexibility. Crosslinked silicone coatings and surfacegrafted coatings were prepared with amphiphilic linear PEO-silanes (a-c). Crosslinked silicone coatings were also prepared with branched PEO-silanes (1a-3a and 1b-3b). All coatings showed improved resistance to common plasma proteins compared to silicone coatings. Furthermore, protein adsorption generally decreased with siloxane tether length. For crosslinked PEO-modified silicone coating systems based on linear (a-c) and branched PEO-silanes (1a-3a and 1b-3b), longer tethers enhanced PEO reorganization to the film-water interface to enhance protein resistance. In the absence of surface reorganization for surface grafted coatings prepared with linear PEO-silanes, longer siloxane tethers better inhibited protein adsorption despite a moderate decrease in graft density (sigma) and decrease in surface hydrophilicity. This indicates that longer siloxane tethers enhance the configurational mobility of the PEO segments to better repel proteins.

Rolling contact is experienced by a large number of components in mechanical designs. Examples include roller bearings and ink distribution rollers in the printing industry. Rolling contact results in surface wear. It is however possible to reduce rolling contact wear rates and surface fatigue by performing a surface modification such as powdered metal coating [35]. Powder coating methods such as Laser cladding and Plasma coating are two application processes that are completely different in method and therefore create different coating microstructures and bonding mechanisms between the coating and substrate. The aim of the research was to investigate the comparative rolling contact performance of two coating processes and two separate metal powder compositions. The coatings were applied to British standard En 9 steel test specimens. En 9 was selected due to its popular use in the manufacture of shafts, cylinders and rollers. Under rolling contact, material is removed from the surface as a result of wear and surface fatigue. Through testing and evaluation, the performance of the coating application processes were evaluated relative to one another and relative to the uncoated steel under rolling contact. The performance of the coating compositions were also evaluated against one another for a given coating application process. Results used to determine the performance of the coatings and coating processes were, the number of cycles to failure and the wear rates of the coated surface. Microstructure pictures of the coated surface were taken prior to testing and following testing. The pictures were used to qualitatively determine the effects of the rolling contact on the surfaces. Through the study of rolling contact, an explanation of the stresses induced in the contact area and the position of the maximum values were determined. The boundaries for the deformation regimes were identified through the understanding of the position of first yield and the shakedown limit under rolling contact. The theories of rolling contact fatigue are covered briefly as part of a better understanding of the failure mechanism however the experimentation is largely comparative based. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2008.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xviii, 212 p.; also includes graphics (some col.). Includes bibliographical references (p. 202-212). Available online via OhioLINK's ETD Center

The thesis aims to illustrate and highlight the potential of graphene-based fillers in reinforcing organic coatings deposited by cataphoresis. Thanks to particular surface modification processes of the graphene flakes, these have been properly distributed within the polymer matrix, providing the composite coating with remarkable protective performance. The optimization of the deposition process parameters, as well as the amount of filler, also allowed to improve the mechanical and conductivity properties of the cataphoretic matrix, suggesting the possibility of realizing multifunctional coatings. Finally, these ’smart’ coatings were made by combining two deposition techniques, creating two layers with distinct purposes, containing different types of graphene-based fillers. The cataphoretic primer provided the substrate with high corrosion protection, while the spray top coat possessed high properties of electrical conductivity and resistance to abrasion phenomena. Ultimately, graphene has proven to be an excellent resource as a reinforcing filler in multifunctional organic coatings.

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