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ORGANIC/INORGANIC HYBRID COATINGS FOR ANTICORROSION APPLICATIONS

ALRASHED, MAHER M.
http://rave.ohiolink.edu/etdc/view?acc_num=akron1491226580793534

Abstract Details

2017, Doctor of Philosophy, University of Akron, Polymer Engineering.
Chromate conversion coatings (CCCs) is a multilayer system composed of a pretreatment (conversion) layer, an epoxy primer layer, and a polyurethane top coat layer. Although the CCC system shows high performance and a good defense against corrosion, direct exposure to chromium is known to increase the risk of lung cancer. However, in recent years, sol-gel methods have been utilized to synthesize organic/inorganic hybrid coating systems, such as polyurethane/polysiloxane hybrid coatings. Although polyurethane/polysiloxane hybrid coatings have good optical and mechanical properties, these materials offer less corrosion performance. Thus, these coating systems need further improvements or modifications. In the first part (Chapter III and Chapter IV), passive modification was implemented by introducing graphene oxide (GO) and isocyanate-treated graphene oxide (FGO) to the hybrid coating. The addition of only 0.67 wt% GO reduces the oxygen transmission rate by 50% and water vapor transmission rate by 10%. Although the hybrid coating barrier properties improved with the introduction of nanofillers, the corrosion performance generally decreased. The highly oxygenated surfaces of nanofillers worked as the binding sites and catalysts for TEOS oligomer condensation. This challenge was overcome by reducing nanofillers using microwaves reduction method which also enhanced hydrophobicity and achieved superior barrier properties. The results show that the barrier properties of hybrid coatings against oxygen and water were improved substantially with the addition of only 0.67 wt% reduced nanofillers. A polyurethane/polysiloxane hybrid coating with a 1.5 wt% reduced graphene oxide shows very stable capacitive behavior even after 100 days. In the second part (Chapter V and Chapter VI), nanoparticles (nanocontainers) impregnated with a suitable inhibitor were utilized to enhance the passive performance of hybrid coating. An effective organic inhibitor, 2-mercaptobenzothiazole (MBT), was encapsulated in polylactic acid (PLA) nanoparticles produced via nanoprecipitation. Nanoparticle size distribution, inhibitor loading percentage, and encapsulation efficiency were studied as function of polylactic acid concentration, solvent/antisolvent volume ratio, and the PLA/MBT mass ratio. The addition of polylactic acid nanoparticles into a hybrid coating had minimal effects on the general coating properties. However, the induction time (¿) increased approximately 200 fold, from 12 to 2400 seconds. Finally,biodegradable and non-toxic nanoparticles were produced using ionic gelation method by combining chitosan and lignosulfonate as polycation and polyanion, respectively. The influence of various factors on the gelation process and the size, morphology, stability and composition of the nanoparticles was investigated. The interactions between chitosan and lignosulfonate are primarily coulombic with some contributions from hydrogen bonds. A dense hydrophobic core highly concentrated with lignosulfonate surrounded by a positively charged hydrophilic shell consist of chitosan chains explained the possible structure for these nanoparticles.
Sadhan Jana, Dr (Advisor)
Mark Soucek, Dr (Committee Chair)
Alamgir Karim, Dr (Committee Member)
Tianbo Liu, Dr (Committee Member)
Edward Evans, Dr (Committee Member)
241 p.
Aerospace Materials; Nanoscience; Nanotechnology; Polymer Chemistry; Polymers
Corrosion, Hybrid coating, nanoparticles, graphene oxide, reduced graphene oxide

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Citations

  • ALRASHED, M. M. (2017). ORGANIC/INORGANIC HYBRID COATINGS FOR ANTICORROSION APPLICATIONS [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1491226580793534

    APA Style (7th edition)

  • ALRASHED, MAHER. ORGANIC/INORGANIC HYBRID COATINGS FOR ANTICORROSION APPLICATIONS. 2017. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1491226580793534.

    MLA Style (8th edition)

  • ALRASHED, MAHER. "ORGANIC/INORGANIC HYBRID COATINGS FOR ANTICORROSION APPLICATIONS." Doctoral dissertation, University of Akron, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1491226580793534

    Chicago Manual of Style (17th edition)

akron1491226580793534
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This open access ETD is published by University of Akron and OhioLINK.