Engineering Commons^™

Plasma Treatment Of High-Density Polyethylene, Linear Low-Density Polyethylene, And Polyvinyl Chloride Geomembranes By Air And Oxygen, Merve Koca Uyar

USF Tampa Graduate Theses and Dissertations

High-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), and polyvinyl chloride (PVC) geomembranes were treated with air and oxygen plasma. The purpose of air and oxygen plasma treatment of geomembrane surface is to increase the surface wettability of these materials, thereby increasing adhesive properties. Increasing adhesive properties enables a surface to be coated with a desired material with antibacterial, antioxidant, and UV resistant characteristics, without changing bulk material properties. To protect the geomembranes from oxidation degradation, UV degradation and biological degradation, it is important to increase the antibacterial, antioxidant, and UV resistant properties of geomembrane. Before and after the plasma treatments …

An Investigation Of Cross-Links On Crystallization And Degradation In A Novel, Photocross-Linkable Poly (Lactic Acid) System, Nicholas Baksh

USF Tampa Graduate Theses and Dissertations

Polymeric molecular structure consists of repeating units bonded together. Mechanicalproperties can be altered without affecting chemical makeup by altering the number of these units. Small molecules can be introduced and/or polymers can be modified to form bonds between molecular chains. Cross-linking, as this is called, also introduces mechanical variation with minimal effects on chemical composition. Lastly, polymer chains reorient themselves in response to intermolecular forces. This temperature dependent response is known as crystallization. Although chemistry is unaltered, mechanical properties can depend highly on the percent of the sample that is crystallized.

Cross-linking is known to enhance the mechanical properties of …

Sorption Of Benzene, Toluene, Ethylbenzene And Different Ratios Of Mixture Solvent By Plasticized Pema Films Using A Qcm Sensor, Xinpeng Li

USF Tampa Graduate Theses and Dissertations

VOCs (volatile organic compounds) can cause great harm to human health especially benzene, toluene and ethylbenzene. In this work a Quartz Crystal Microbalance (QCM) sensor with a polymer/plasticizer film was developed to quantify the VOCs both in air and water. QCM is an acoustic wave sensor that can be used well in detecting the aromatic compounds in the film. Because more than one VOC is present in the air, this thesis focuses on finding the sorption of different ratios of VOCs (benzene, toluene, ethylbenzene) using a polymer/plasticizer film in QCM. Poly (ethyl methacrylate) (PEMA) was used as the polymer because …

Effects Of Support Fluid Type On Concrete Integrity And Durability In Drilled Shafts, Sarah J. Mobley

USF Tampa Graduate Theses and Dissertations

Until recently, concrete flow in tremie-placed drilled shafts has been mischaracterized as rising uniformly with laitance formation occurring only at the top of the rising concrete in the shaft. In actuality, concrete first fills a portion of the reinforcement cage to a sufficient height to promote radial flow into the cover region. Depending on support fluid type, the radial flow can produce laitance-filled creases/channels projecting the reinforcing cage configuration to the side of shaft surface. The flow pattern (and creases) can affect filter cake thickness, cover quality and propensity for corrosion. This research examines 52 tremie-placed laboratory drilled shaft specimens …

A Theoretical And Practical Analysis Of The Effect Of Drilling Fluid On Rebar Bond Strength, Kelly Costello

USF Tampa Graduate Theses and Dissertations

Drilled shafts are large cylindrical cast-in-place concrete structural elements that can be favored due to cost-effectiveness. These elements however, require strict quality control during construction to ensure a stable excavation. Drilling fluid is often used in construction to attain this stability. Drilling fluid, or slurry, can be ground water or salt water, but is typically made from a mixture of water and mineral or polymer powder to form a viscous fluid slightly more dense than ground water. During concreting, the drilling fluid is displaced by the heavier concrete, which is tremie placed at the base of the excavation from the …

Sorption Of Benzene, Toluene And Ethylbenzene By Plasticized Poly (Ethyl Methacrylate) Using Quartz Crystal Microbalance At 298.15k, Kiranpreet Kaur

USF Tampa Graduate Theses and Dissertations

Quartz crystal microbalances (QCM) are chemical sensors used for liquid and vapor sensing. In this thesis work, plasticized poly (ethyl methacrylate) (PEMA) coated QCM was used to study sorption behavior of benzene, ethylbenzene and toluene in respective polymer at 298.15K. Poly (ethyl methacrylate) (PEMA) is a promising polymer with solubility parameter close to BTEX compounds, but it's glassy and rigid nature at room temperature make it less sensitive. The addition of plasticizers (Diisononyl cyclohexane-1,2-dicarboxylate (DINCH) and Diisooctyl azelate (DIOA)) lowers the glass transition temperature, provides flexibility and thus increases the free volume of the polymer to enhance analyte sorption. In …

Measuring Polydimethylsiloxane (Pdms) Mechanical Properties Using Flat Punch Nanoindentation Focusing On Obtaining Full Contact, Federico De Paoli

USF Tampa Graduate Theses and Dissertations

In this research, the materials used were the Polydimethylsiloxane (PDMS) polymers. PDMS mechanicals properties were measured using a customized version of the nanoindentation test using a flat punch tip. The method is proposed in Chapter 3 and it is used to calculate the elastic modulus of different PDMS samples. The samples tested were both produced specifically for this research and available in the laboratory’s storage. They all present different levels of cross-linking degree.

It is quite common to not have full contact between the cylindrical flat punch and the sample because of the unavoidable tilt. The new method guarantees establishing …

Investigation Of Energy Alignment Models At Polymer Interfaces, Wenfeng Wang

USF Tampa Graduate Theses and Dissertations

The presented study investigated the Induced Density of Interface States (IDIS) model at different polymer interfaces by using photoemission spectroscopy in combination with electrospray deposition.

In recent years, organic electronics have attracted considerable attention due to their advantages of low-cost and easy-fabrication. The performance of such devices crucially depends on the energy barrier that controls the interface charge transfer. A significant effort has been made to explore the mechanisms that determine the direction and magnitude of charge transfer barriers in these devices. As a result of this effort, the IDIS model was developed to predict the energy alignment at metal/organic …

Macroencapsulation Of Phase Change Materials For Thermal Energy Storage, Swetha Pendyala

USF Tampa Graduate Theses and Dissertations

The use of a latent heat storage system using phase change materials (PCMs) is an effective way of storing thermal energy. Latent heat storage enables high-energy storage density which reduces the footprint of the system and the cost. However, PCMs have very low thermal conductivities making them unsuitable for large-scale use without enhancing the effective thermal conductivity. In order to address, the low thermal conductivity of the PCMs, macroencapsulation of PCMs has been adopted as an effective technique. The macroencapsulation not only provides a self-supporting structure of PCM and separates the PCM from thermal fluids but also enhances the heat …