Browsing by Subject "Epoxy"
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Item Dispersion and Characterization of Nickel Nanostrands in Thermoset and Thermoplastic Polymers(2012-02-14) Whalen, Casey AllenNickel Nanostrands (NiNS) are nano-particles that are highly branched and have a high aspect ratio. These particles show promise as excellent additives to composites when electrical conductivity is desired. Unfortunately, there is very little research done on dispersing powdered NiNS in various polymer matrices. This thesis covers the research in dispersing NiNS in three separate polymer systems, and related composite processing and characterization. An aromatic polyimide (CP2) is first used as a thermoplastic matrix and attempts to incorporate NiNS via an in-situ processing technique concurrent with in-situ polymerization are detailed. Epoxy is then used as a representative thermoset where the NiNS are dispersed in the resin before a hardener is added. The last polymer tested is thermoplastic Polyvinylidene Fluoride (PVDF). NiNS are introduced to this polymer in a solution mixture. Once dispersed, the PVDF solution is heated until the solvent evaporates leaving a PVDF melt containing NiNS, which is subsequently cooled. Samples of all three polymer nano-composites are created and dispersion is observed with an optical microscope. Using DSC, DMA and dielectric spectroscopy, thermal, mechanical and electrical properties are measured and analyzed. Results for the CP2 nano-composites showed that during the cure phase, the NiNS settled to the bottom of the films resulting in a non-dispersed composite. This result highlighted the difference between NiNS and other more conventional nano-particles, namely that the NiNS are larger and heavier, therefore are not 'locked into' a dispersed state by the polymer chains. Several techniques were investigated for dispersing NiNS in the epoxy matrix. A method without solvent was shown to be the most effective and resulted in a well-dispersed nano-composite that showed increases in electrical conductivity and dielectric constant as NiNS concentration increases. Enhancement in storage modulus was observed above the composite's Tg as well. PVDF nano-composites also showed good dispersion and a general increase in electrical properties. Below Tg, storage modulus decreases at first before a slight recovery with increasing NiNS. Beyond Tg, the opposite effect is observed. FTIR measurements for the PVDF were also taken and showed no significant changes in the polymer morphology with additions of NINS.Item Quality control test for carbon fiber reinforced polymer (CFRP) anchors for rehabilitation(2009-12) Huaco Cárdenas, Guillermo David; Jirsa, J. O. (James Otis); Bayrak, OguzhanDifferent strategies can be used to repair, rehabilitate and strengthen existing structures. Techniques based on Fiber Reinforced Polymer (FRP) materials appear to be innovative alternatives to traditional solutions because of their high tensile strength, light, weight, and ease of installation. One of the most common and useful FRPs is Carbon Fiber Reinforced Polymer (CFRP) used in sheets and anchors attached on the concrete surface to strengthen the section through addition of tensile capacity. The purpose of this study was develop a technique for assesses the strength of anchors for quality control purpose. However, to transfer tensile capacity to a concrete surface, the sheets are bonded to the surface with epoxy adhesive. As tension increase, CFRP sheets lose adherence of the epoxy from the concrete surface and finally debond. To avoid this failure, CFRP anchors are applied in addition at the epoxy. The CFRP anchors allow the CFRP sheets to utilize their full tensile capacity and maximize the material efficiency of the CFRP retrofit. The number and size of anchors play a critical role. However the capacity of CFRP anchors has not been investigated extendedly. A methodology for assessing the quality of CFRP anchors was developed using plain concrete beams and reinforced externally with CFRP sheets attached with epoxy and CFRP anchors. Applying load to the beam, allowed the development a tensile force in the CFRP sheets and a shear force on the CFRP anchors. The shear forces in the CFRP anchors were defined by the load applied to the beam and compared with forces based on measured stress in CFRP sheets.Item The Evaluation of the Mechanical Strength of Epoxy-Based Resin as a Plugging Material, and the Development of a Novel Plug and Abandon Technique Using Vitrified Solid Epoxy-Based Resin Beads(2012-07-16) Abuelaish, AhmedOver the past several years, some of the platforms in the Gulf of Mexico have been damaged completely, such that conventional P&A operations may not be possible. In these cases, plugging fluid needs to be pumped through an intervention well and dropped several thousand feet in water to settle above a packer and seal the well. The current P&A material of choice is cement, but cement is miscible in water, which dilutes and contaminates the cement. Therefore, alternate plugging materials need to be used for these operations. This paper discusses the development of a cost-effective Epoxy P&A method and the challenges of using Epoxy. First, the impact of seawater, oil, and pipe dope on the curing process remains unknown. Secondly, the yield strength of Epoxy with and without the contaminating chemicals must be equal to or better than cement. Finally, previous tests have shown significant losses of Epoxy to the walls of the wellbore during the 7,000-ft drop. 2 High temperature curing and compression tests were performed on contaminated epoxy samples to determine the effectiveness of the epoxy plug. To reduce material losses, an improved method for introducing the epoxy into the target zone was developed. This method takes advantage of a narrow window in the cure process where the curing process can be suspended by quenching the partially cured liquid epoxy in water at room temperature, thereby changing the liquid epoxy into solid beads. The beads can then be pumped into the wellbore, where they liquefy at wellbore temperature, 200?F, then cure into a solid plug. Seawater was found to accelerate the cure time, while all contaminants tested reduced the fracture strength by more than 25% compared to pure resin. The yield strengths of contaminant mixtures, however, remained relatively constant, with the greatest drop being only 11%. The use of solid epoxy beads was found to have a compressive strength 50% greater than Portland cements I&II. In addition, the application mentioned herein eliminates the need to prepare the plug material on site. These advantages greatly contribute to reducing the costs of an epoxy P&A operation, to potentially being USD 0.7 million cheaper than a Portland cement operation.Item Toughening of Epoxies Based on Self-Assembly of Nano-Sized Amphiphilic Block Copolymer Micelles(2010-01-16) Liu, JiaAs a part of a larger effort towards the fundamental understanding of mechanical behaviors of polymers toughened by nanoparticles, this dissertation focuses on the structure-property relationship of epoxies modified with nano-sized poly(ethylene-altpropylene)- b-poly(ethylene oxide) (PEP-PEO) block copolymer (BCP) micelle particles. The amphiphilic BCP toughener was incorporated into a liquid epoxy resin and selfassembled into well-dispersed 15 nm spherical micelle particles. The nano-sized BCP, at 5 wt% loading, can significantly improve the fracture toughness of epoxy (ca. 180% improvement) without reducing modulus at room temperature and exhibits only a slight drop (ca. 5 ?C) in glass transition temperature (Tg). The toughening mechanisms were found to be BCP micelle nanoparticle cavitation, followed by matrix shear banding, which mainly accounted for the observed remarkable toughening effect. The unexpected ?nano-cavitation? phenomenon cannot be predicted by existing physical models. The plausible causes for the observed nano-scale cavitation and other mechanical behaviors may include the unique structural characteristics of BCP micelles and the influence from the surrounding epoxy network, which is significantly modified by the epoxy-miscible PEO block. Other mechanisms, such as crack tip blunting, may also play a role in the toughening. Structure-property relationships of this nano-domain modified polymer are discussed. In addition, other important factors, such as strain rate dependence and matrix crosslink density effect on toughening, have been investigated. This BCP toughening approach and conventional rubber toughening techniques are compared. Insights on the decoupling of modulus, toughness, and Tg for designing high performance thermosetting materials with desirable physical and mechanical properties are discussed.