Master of Science in Polymer Engineering, University of Akron, 2018, Polymer Engineering

Polyvinyl chloride (PVC) is an important polymer used to produce digital printable flexible films. It is often chosen due to its favorable cost to performance ratio. In order to produce films that meet a wide range of applications, several additives are typically incorporated into the formulation. These additives are often migratory, most notably plasticizers, which are added to PVC to improve its flexibility. Pressure-sensitive adhesives (PSA) are coated onto the backside of the PVC film so that the film can be applied to various substrates. The goal was to improve the stability of the PVC films by addition of nanoclay which acts to form a barrier layer. This included consistent print surface, mechanical properties, and adhesive properties. Two different approaches were investigated to incorporate nanoclay into the PVC film products. The first was to disperse nanoclay directly into the PVC film. The film was made by preparing an organosol formulation and casting onto a rigid film web. The second approach was to disperse nanoclay into a thin polymer coating which was applied to the backside of the PVC film. The nanocomposite structures were characterized by microscopy techniques including AFM, SEM and TEM. The mechanical and adhesive properties were evaluated as a function of thermal aging. The thermal stability, durability, barrier, and surface properties were also evaluated.

Committee: Sadhan Jana Dr. (Advisor); Erol Sancaktar Dr. (Committee Member); Younjin Min Dr. (Committee Member) Subjects: Polymers

PhD, University of Cincinnati, 2014, Engineering and Applied Science: Materials Science

This research is focused on the synthesis, characterization and properties of epoxy based coatings, blended and cured with thermoplastic nylon-6 and organoclay modified nylon-6. Epoxy resins has 2 major drawbacks: (1) extremely brittle nature and (2) moisture absorption. The first problem is solved by incorporation of nylon-6 in epoxy, and the second problem is solved by incorporation of nano-clay in the nylon-6/epoxy system. A novel polymerization process of synthesizing nylon-6 in solution was developed in this work, which resulted in simple and efficient process of blending nylon-6 with epoxy resin resulting in homogenous blends of nylon-6 with epoxy. The storage modulus in glassy region for nylon-6/epoxy composites decreased linearly as nylon-6 weight % increased, along with decrease in glass transition temperature from 70 ?C to 30 ?C. The storage modulus in rubbery region increased compared to control epoxy. The control epoxy used in the system was water based EPIREZ5522-WY-55, thermally heated without using curing agent. The curing agent was not used to study the effect of nylon-6 on storage modulus in rubbery region. These results indicated that sole nylon-6 increased cross-link density of epoxy resin, which was further verified by determining fractional epoxy conversion by monitoring characteristic epoxy peak at 914 cm-1 in FTIR, which increased with increase in nylon-6 wt.%. The nylon-6/epoxy coatings applied on Al-2024 T3 substrate were tested for anti-corrosion. The coating containing 10% of nylon-6 in epoxy showed the best performance, compared to other compositions, thermally heated epoxy coating and epoxy-amine system. Comparison with formulation cured by thermal treatment of epoxy showed that nylon-6 alone without standard curing agent is effective in improving the properties, while comparison with standard epoxy-amine system suggested that the novel technology can be effectively used in practical applications. Then clay/nylon-6 nanocomposites were s (open full item for complete abstract)

Committee: Jude Iroh Ph.D. (Committee Chair); F James Boerio Ph.D. (Committee Member); Raj Manglik Ph.D. (Committee Member); Rodney Roseman Ph.D. (Committee Member) Subjects: Materials Science

Master of Science, University of Akron, 2014, Polymer Engineering

Abstract In recent years, clay filled polymer nanocomposites are manufactured for a variety of advanced applications due to the abundant resource in nature, platelet structure bearing high aspect ratio, high efficiency, and promising ion-exchange capacity of clay minerals, especially Montmorillonite. To achieve a moderate level of clay dispersion, one of the most ubiquitous approaches is to modify the surface of the layered silicates by exchanging inter-gallery metal cat ions with quaternary ammonium salts. The resultant product is commonly referred to as organoclay. However, the existence of small organic molecules, such as alkyl-ammonium salt in the polymer, leads to vitiation of thermal properties and unnecessary hydrophobicity, in addition to involving tedious ion-exchange and drying process during the preparation of surfactant modified clay. To resolve these issues, in this work, we have developed an ultra-sonication assisted film casting technique to achieve well-intercalated nanostructure of polymer/clay nanocomposites. According to the chemical structure of natural Montmorillonite, hydroxyl groups are present among the negatively charged silicate layers. These hydroxyl groups, if made accessible to the polymer chains area wise, can promote polymer-clay surface interactions for polymers with polar repeating units via hydrogen-bonding. Using ultra-sonication film casting technique, we have dispersed natural Montmorillonite in zinc-neutralized sulfonated EPDM ionomer (Zn-S-EPDM) and polycaprolactone. We also have proved that this technique is applicable to the traditional polymer/organoclay system through the preparation of polystyrene/Cloisite 10A nanocomposites. The morphology and properties of these composite systems are characterized using wide angle X-ray diffraction (WAXD), transmission electron microscope (TEM), tensile test, dynamic motion analysis (DMA), and strain-induced buckling instability for modulus measurements (SIBIMM). We (open full item for complete abstract)

Committee: Alamgir Karim Dr. (Advisor); Yu Zhu Dr. (Committee Member); Kevin Cavicchi Dr. (Committee Member) Subjects: Polymers

MS, University of Cincinnati, 2008, Engineering : Materials Science

In this thesis we report the change in the orientation of the polymer lamellae and clay platelets from a PE-Nanocomposite film to that in the pressed composite sample, when a number of such films are hot pressed to form a pressed sample (strip), about 5 mm in thickness. Small-angle x-ray scattering (SAXS) was used to compare the quantitative and qualitative information regarding the structure and orientation of these structures in the film and the pressed strip. It was observed that the polymer lamellar normals in the composite film which were oriented in the MD get oriented in the ND in the pressed film sample. Diffraction studies carried out on both the samples show that the clay platelet normals for the film samples show a stronger orientation in the ND than for the pressed film sample. The tensile properties of the PE-Nanocomposite pressed sample (strip) and that of the Polyethylene (HDPE) film pressed sample (strip) was measured using an instron tensile machine and the values compared. The composite showed an increase in the modulus as compared to that observed in the virgin HDPE sample.

Committee: Gregory Beaucage PhD (Advisor); Jude Iroh PhD (Committee Member); Rodney Roseman PhD (Committee Member) Subjects: Materials Science

Doctor of Philosophy, The Ohio State University, 2009, Chemical Engineering

In recent years there has been increased interest in the broad areas of micro- and nano-technology due to the potential to create materials with unique properties which were previously unattainable. One area of special interest has been the use of nanoparticles such as nanoclays, nanofibers and carbon nanotubes and microscale carbonyl iron particles. Nanoclays and nanofibers have received attention due to their ability to be incorporated into polymer matrices and impart functionality such as electrical conductivity, increased tensile strength and modulus, and a reduction of gas and moisture permeability at much lower particle loadings when compared to traditional fillers such as carbon black and glass fibers. The addition of these nanoparticles also has a significant effect on the rheological properties of the composite. The rheological behavior of polystyrene/nanoclay composites under steady state shear flow and polystyrene/carbon nanofiber composites under transient shear and uniaxial extension is investigated. A constitutive model is developed that is capable of predicting the shear and extensional rheology of both types of composites and predicts orientation changes to the nanoparticles due to flow. The model is validated through comparison to the experimental rheological measurements of both composite types and experimental measurements of carbon nanofiber orientation in the polystyrene/carbon nanofiber composites under uniaxial extension.The addition of magnetizable carbonyl iron particles to a non-magnetizable carrier fluid has been done to create a smart fluid, known as a magnetorheological fluid, whose rheological properties can be modified through the application of a magnetic field. This added functionality is being utilized in applications such as shock absorbers, dampers, brakes, and clutches. The use of these fluids in engineering applications requires rheological models capable of capturing their complex flow behavior under various flow conditions. Th (open full item for complete abstract)

Committee: Dr. Kurt Koelling (Advisor); Dr. Stephen Bechtel (Committee Member); Dr. L. James Lee (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, The Ohio State University, 2007, Chemical Engineering

The polymer foam industry is slowly implementing carbon dioxide (CO2) as a low-cost, safe, and environmentally friendly blowing agent alternative to fluorocarbons and hydrocarbons. Progress is slow due to several obstacles, ranging from low blowing agent solubility to a lack of quantitative understanding of the influence of carbon dioxide on viscosity. A crucial property in foam extrusion is viscosity. Several research groups have published viscosity data of polymer melts under high pressure, using a variety of techniques. However, few studies assist in designing polymer processing equipment because most do not contain predictive scaling (e.g., WLF-analogous scaling factors) to apply to different operating conditions. A new high-pressure rotational rheometer has been applied to polystyrene and carbon dioxide at five concentrations. It provides direct measurement of the zero shear viscosity of the polymer under a high pressure diluent. The method allows many viscosity measurements to be performed on a single sample. Scaling factors are applied to the data and the WLF-Chow equation is found to describe the results when the appropriate parameter is selected. Due to an interest in using organoclay nanoparticles for foaming, the viscosity of the polystyrene-nanoclay-CO2 system is studied using the couette rheometer and an extruder slit die. At high shear rates (10 to 100 s-1), the viscosity of polystyrene-nanoclay-CO2 unexpectedly possesses a lower viscosity than polystyrene-CO2 at the same concentration. At low shear rates (10-3 to 1 s-1), this effect is not observed. It is suspected that interfacial slip is occurred at the interface at high shear rates. Polymer additives allow tuning of bubble morphology without changing operating conditions. In this study, either a second polymer or nanoparticles are studied. Poly (methyl methacrylate) (PMMA) has the ability to drastically reduce cell size of polystyrene (PS) foams. It is believed that heterogeneous nucleation occurs (open full item for complete abstract)

Committee: David Tomasko (Advisor) Subjects: Engineering, Chemical

Doctor of Philosophy, University of Akron, 2009, Polymer Engineering

This research provides an in-depth analysis on the effects of organoclay inclusion in PLA film on the evolution of structural hierarchy during constant and variable rate uniaxial and biaxial stretching processes. At lower deformation rates and/or higher temperatures PLA exhibits three regime stress-optical behavior: In Regime I, the material remains amorphous while obeying the traditional linear Stress Optical Rule (SOR), in Regime II strain crystallization occurs in conjunction with a positive deviation from SOR, and in Regime III, birefringence increases slowly with stress as the chains reach their finite extensibilities or are locked in place by an oriented crystalline network. This is due to partial chain relaxation at these conditions which allows the highly oriented adjacent chains to register themselves into the crystal lattice formation. Lower temperature and/or higher rates, on the other hand, evoke a nematic-like phase consisting of high orientation but significant translational disorder, bringing about Regime I-III behavior with absence of Regime II. As the organoclay filler content increases, higher temperatures and/or lower rates are required to overcome the confinement effect on the PLA chains in the vicinity of the high aspect ratio organoclay platelets and/or to relax the chains that are quickly being pulled and oriented by the clay. The 3D ordered crystal zones in filled material don't all orient in the MD, as many of the PLA chains that are entangled between and interconnected with the organoclay platelets' surfaces deform and crystallize away from the MD as the platelets separate during stretching. This phenomenon leads to lower Regime I-II slopes and end-birefringence values with an increase in clay loading. Application of very low stretch rates early on in the deformation process (Exponential (EXP) profile) was found to delay the strain crystallization mechanism which leads to rapid orientation development in the material. For the same value of (open full item for complete abstract)

Committee: Mukerrem Cakmak PhD (Advisor) Subjects: Polymers

Master of Science in Polymer Engineering, University of Akron, 2008, Polymer Engineering

This study evaluated the effects of Nanofil® nanoclay on morphology development of an immiscible polymer blend of polypropylene (PP) and polystyrene (PS). The hypothesis that smaller dispersed phase domains are formed in the blending of immiscible polymers in the presence of nanoclay was examined in this work. A much studied immiscible polymer system of PP and PS was considered in conjunction with a commercial nanoclay. The nanoparticles studied were the surface modified montmorillonites from Sud-Chemie, Nanofil® SE 3000 and Nanofil® SE 3010. The commercial nanoclay was reported to work well for PP/PS blends, although it was anticipated at the outset that nanocomposites would not be produced. The compounds were prepared using a co-rotating twin screw extruder under commercially viable conditions. It was found that smaller dispersed domains were formed in the presence of nanoparticles, but that the effect was composition dependent. The blend with a 55/45 ratio by weight of PP/PS showed a change of morphology from co-continuous to droplet-matrix type upon the addition of nanoclay. The blend with a 75/25 ratio by weight of PP/PS showed a more definite reduction of minor phase size. Additionally, in some cases, the nanoparticles were found to be at the interface, which was an indication that the nanoparticles did not have an affinity for PP or PS. The morphology was examined by scanning electron microscopy, wide angle X-ray diffraction and transmission electron microscopy, and the thermal properties were characterized by differential scanning calorimetry. The mechanical and rheological properties were also evaluated. Nanofil® SE 3000 was found to be superior to Nanofil® SE 3010 as it gave rise to smaller dispersed phase size. Pre-compounding the nanoclay into the polystyrene phase was found to be beneficial.

Committee: Sadhan Jana PhD (Advisor); Erol Sancaktar PhD (Committee Member); Kyonsuku Min PhD (Committee Member) Subjects: Plastics; Polymers

Doctor of Philosophy, University of Akron, 2008, Polymer Engineering

Shape memory polymers are smart materials which can remember their original shapes. However, the low recovery stress and low mechanical strength limit the commercial applications of shape memory polymers. In this study, nanoclays were introduced to shape memory polyurethanes (SMPU) to augment these properties by enhance the network of SMPU. Several factors which influence the shape recovery stress were evaluated, including the nature of polymer chain by using different monomers, type of clay particles, extent of filler dispersion, clay content and deformation conditions. It was found that only reactive clay particles were well dispersed into polyurethane matrix by the tethering between –CH 2CH 2OH functional groups in clay surfactants and polyurethane chains. Two different shape memory polyurethanes ( Systems I & II) prepared by bulk polymerization were compared. The shape memory effect of System Iwas triggered by melting of the soft segment crystals, while that of System IIwas by glass transition of the soft segments. It was seen that the reactive clay particles dispersed well in both polyurethane matrices and augmented the recovery stress, e.g., 20% increase with 1 wt % nanoclay in System Iand 40% increase with 5 wt % nanoclay in System IIwere observed. In System I, clay particles interfered with soft segment crystallization, and promoted phase mixing between the hard and soft segments, thus affecting the fixity and recovery ratio. Nevertheless, the soft segment crystallinity was still enough and in some cases increased due to stretching to exhibit excellent shape fixity and shape recovery ratio. The higher loading of clay particles accelerated the stress relaxation, resulting in reduction of recovery stress. In System II, no significant effect of clay particles in phase separation was observed, so there was no influence of clay on shape fixity and recovery ratio. The recovery stress increased with reactive nanoclay content. It was also found that the recovery str (open full item for complete abstract)

Committee: Sadhan Jana (Advisor) Subjects: Engineering, Materials Science