Study Of The Structure-Property Relationships That Determine The Effects Of Latexes And Starch Containing Latex Emulsions On The Performance Of The Barrier Coatings (Sub-Coat) For Paper,
2014
University of Southern Mississippi
Study Of The Structure-Property Relationships That Determine The Effects Of Latexes And Starch Containing Latex Emulsions On The Performance Of The Barrier Coatings (Sub-Coat) For Paper, Joanna Marie Monfils
Master's Theses
The history of carbonless paper dates back to the 1940s. Before this, a carbon copy sheet was needed between sheets of paper to be able to produce one or more copies simultaneously during writing. The pressure from a pen or typewriter would help deposit the ink of the carbon paper onto the blank sheet of paper under the original written sheet to create a “carbon copy.” This method did however, have its disadvantages. Not only did it produce a limited number of copies, but it was also a messy process. So came the creative process of using microencapsulated dyes to …
Optimizing Polymer Fluorescence For Explosives Detection,
2014
University of Connecticut
Optimizing Polymer Fluorescence For Explosives Detection, Rose K. Cersonsky
Honors Scholar Theses
Pyrene is commonly used for explosives detection, as when mixed with polystyrene, the fluorescence intensity of the resulting film can be used as an indicator of the presence of nitro-aromatic, nitro-ether, or nitro-amine explosives. Previous studieshave tested a three-component system including pyrene, polystyrene, and a salt, tetrabutylammonium hexafluorophosphate (TBAHP). From these previous studies, it has been seen that vapor pressure of the preparation area is a governing factor in the formation of excimers, which are instrumental in achieving and maintaining fluorescence intensity. In this study, three parameters – solution concentration, film thickness, and molecular weight of polystyrene are examined to …
Humidity Effect On The Structure Of Electrospun Core-Shell Pcl-Peg Fibers For Tissue Regeneration Applications,
2014
The University of Western Ontario
Humidity Effect On The Structure Of Electrospun Core-Shell Pcl-Peg Fibers For Tissue Regeneration Applications, Adam P. Golin
Electronic Thesis and Dissertation Repository
With the aim of creating a biodegradable scaffold for tympanic membrane (TM) tissue regeneration, core-shell nanofibers composed of a poly(caprolactone) shell and a poly(ethylene glycol) core were created using a coaxial electrospinning technique. In order to create fibers with an optimal core-shell morphology, the effect of relative humidity (RH) on the core-shell nanofibers was systematically studied, with a FITC-BSA complex encapsulated in the core to act as a model protein. The core-shell nanofibers were electrospun at relative humidity values of 20, 25, 30, and 40% RH within a glove box outfitted for humidity control. The core-shell morphology of the fibers …
Modeling The Dynamic Properties Of Monodisperse Linear Polymer Melts With Wedge Spectra,
2014
University of Akron Main Campus
Modeling The Dynamic Properties Of Monodisperse Linear Polymer Melts With Wedge Spectra, J. Frederick, S.-T. Yeh, D. Mcintyre, Marcia Weidknecht
Marcia E. Weidknecht
A mathematical model of the spectrum of relaxation times for molten linear monodisperse homopolymers has been developed which is the sum of two variations of the well-known wedge spectrum. Adjusting the six parameters of the model allows fitting the storage and loss moduli within experimental error over a range of 10-12 logarithmic decades of frequency which encompass the flow, plateau, transition, and glassy zones of viscoelastic behavior. Model parameters are easily determined with a desktop microcomputer using standard nonlinear least-squares fitting procedures. All six model parameters correspond directly to prominent features of experimental data. The plateau modulus, viscosity, steady-state shear …
From Elastic Deformation To Terminal Flow Of A Monodisperse Entangled Melt In Uniaxial Extension,
2014
University of Akron Main Campus
From Elastic Deformation To Terminal Flow Of A Monodisperse Entangled Melt In Uniaxial Extension, Yangyang Wang, Shi-Qing Wang
Shi-Qing Wang
Using a well-entangled monodisperse styrene-butadiene random-copolymer (SBR) melt as a model system, we illustrate generic features of uniaxial extension behavior that may be shared by all well-entangled thermoplastic and elastomeric materials. Depending on the imposed extensional rate, the same sample may behave like a viscous liquid or an elastic "solid." Analogous to the recently revealed shear inhomogeneity, the SBR melt inevitably undergoes cohesive failure in the form of sample breakage whenever the Weissenberg number is much greater than unity, making it challenging to reach steady state. In the elastic deformation regime where the external deformation rate is faster than Rouse …
Interfacial Stick-Slip Transition In Simple Shear Of Entangled Melts,
2014
University of Akron Main Campus
Interfacial Stick-Slip Transition In Simple Shear Of Entangled Melts, Pouyan E. Boukany, Prashant Tapadia, Shi-Qing Wang
Shi-Qing Wang
This article describes a systematic investigation of a discontinuous interfacial stick-slip transition (SST) in simple shear of monodisperse entangled 1,4-polybutadiene (PBD) and polyisoprene (PIP) melts with different molecular weights and architecture, using a specially designed controlled-force shear rheometer. The magnitude of the transition is found to be determined by the level of chain entanglement. Specifically, the dependence of extrapolation length b on molecular weight as b similar to M-w(3.4) and of the melt viscosity as b similar to eta is consistent with the observations based on capillary rheometric studies [X. Yang et al., Rheol. Acta 37, 415-423 (1998)]. The interfacial …
Shear Banding Or Not In Entangled Dna Solutions Depending On The Level Of Entanglement,
2014
University of Akron Main Campus
Shear Banding Or Not In Entangled Dna Solutions Depending On The Level Of Entanglement, Pouyan E. Boukany, Shi-Qing Wang
Shi-Qing Wang
Entangled DNA solutions are ideal as a model system to examine nonlinear shear flow behavior. Even when the number of entanglements per chain, Z, is higher than 100, the solution is still soft enough with an elastic plateau modulus under 100 Pa and is thus amenable to experimental study by commercial rotational rheometry without ambiguity and uncertainty. We have investigated nonlinear flow behavior of three entangled DNA solutions with Z=24, 60, and 156, respectively, using a combination of particle-tracking velocimetric (PTV) and conventional rheometric measurements. We explore questions such as (a) whether shear banding also occurs in moderately entangled solutions, …
Elastic Breakup In Uniaxial Extension Of Entangled Polymer Melts,
2014
University of Akron Main Campus
Elastic Breakup In Uniaxial Extension Of Entangled Polymer Melts, Yangyang Wang, Pouyan Boukany, Shi-Qing Wang, Xiaorong Wang
Shi-Qing Wang
Five entangled melts, with the number of entanglements per chain ranging from 25 to 160, have been studied to illustrate how cohesive strength can be overcome in either continuous or interrupted extension (i.e., during or after uniaxial stretching). The internal elastic stress due to chain deformation from imposed strain appears to be the cause of the observed yielding behavior that reveals scaling laws. The visual signature of the elastic breakup is the occurrence of nonuniform extension. The yield phenomena may be understood at a force level.
Nature Of Steady Flow In Entangled Fluids Revealed By Superimposed Small Amplitude Oscillatory Shear,
2014
University of Akron Main Campus
Nature Of Steady Flow In Entangled Fluids Revealed By Superimposed Small Amplitude Oscillatory Shear, Pouyan E. Boukany, Shi-Qing Wang
Shi-Qing Wang
We carry out a systematic investigation into steady-state shear behavior of six entangled solutions based on a superposition of continuous shear and small amplitude oscillatory shear (SAOS). During steady shear in the shear thinning regime, the superimposed SAOS frequency sweep measurements reveal characteristics of viscous liquids, e. g., terminal dynamics, on the experimental time scale of the reciprocal shear rate. The residual entanglement network retains the same level of elastic stiffness as the equilibrium system does. Consistent with the convective constraint release idea, chains in the network are forced to pass around each other as they must do so to …
A Correlation Between Velocity Profile And Molecular Weight Distribution In Sheared Entangled Polymer Solutions,
2014
University of Akron Main Campus
A Correlation Between Velocity Profile And Molecular Weight Distribution In Sheared Entangled Polymer Solutions, Pouyan E. Boukany, Shi-Qing Wang
Shi-Qing Wang
In this work we attempt to answer several questions concerning the flow characteristics of entangled polymer solutions in a sliding plate shearing cell. We explore (a) how the molecular weight distribution affects the velocity profile in simple shear, (b) whether the observed shear banding is consistent with a nonmonotonic constitutive model, (c) whether the flow response and velocity profiles are different in simple shear depending on the different modes of shear. Our results provide a comparison with recent reports on a polydisperse polymer sample [Tapadia and Wang, Phys. Rev. Lett. 96, 016001 (2006); Tapadia, et al., Phys. Rev. Lett. 96, …
Steady State Measurements In Stress Plateau Region Of Entangled Polymer Solutions: Controlled-Rate And Controlled-Stress Modes,
2014
University of Akron Main Campus
Steady State Measurements In Stress Plateau Region Of Entangled Polymer Solutions: Controlled-Rate And Controlled-Stress Modes, Sham Ravindranath, Shi-Qing Wang
Shi-Qing Wang
Despite decades of efforts, reliable measurements of nonlinear flow behavior of well-entangled polymers in continuous shear have been challenging to obtain. The present work attempts to accomplish three important tasks: (A) overcome this challenge by adopting a strategy of decoupling theological measurements from the outer meniscus region in a cone-partitioned plate (C/PP) setup; (B) determine whether well-entangled solutions indeed undergo a flow transformation under creep that can be taken to phenomenologically define an entanglement-disentanglement transition (EDT); (C) provide the velocity profiles of such solutions undergoing either controlled-stress or controlled-rate shear by carrying out in situ particle-tracking velocimetric (PTV) measurements. Upon …
Yieldlike Constitutive Transition In Shear Flow Of Entangled Polymeric Fluids,
2014
University of Akron Main Campus
Yieldlike Constitutive Transition In Shear Flow Of Entangled Polymeric Fluids, Prashant Tapadia, Shi-Qing Wang
Shi-Qing Wang
We describe an unexpected constitutive transition in entangled polymer solutions. At and beyond a critical stress, the initial spatially homogeneous and well-entangled sample transforms from its entangled (coiled) state into a fully disentangled (stretched) state over a period during which the resulting shear rate increases in a spatially inhomogeneous fashion. In the mode of controlled shear rate, the sample exhibits a stress plateau over three decades. Flow birefringence and normal stress observations unravel additional features of these flow phenomena.
Nonlinearity In Large Amplitude Oscillatory Shear (Laos) Of Different Viscoelastic Materials,
2014
University of Akron Main Campus
Nonlinearity In Large Amplitude Oscillatory Shear (Laos) Of Different Viscoelastic Materials, Xin Li, Shi-Qing Wang, Xiaorong Wang
Shi-Qing Wang
The present work investigates nonlinear behavior in large amplitude oscillatory shear (LAOS) of four different polymeric materials using simultaneous conventional rheometric measurements and particle-tracking velocimetric observations. In contrast to most studies in the literature that treat nonlinearity in LAOS in steady state, we emphasize by the present four examples that nonlinearity in LAOS often arise in complex fluids due to time-dependent rearrangement of their microstructures in response to LAOS. Consequently, no correlation is obvious between strain dependence of the steady-state stress response and the time-dependent characteristics of the steady-state response. For instance, a highly viscoelastic material made of nano-sized polybutadiene …
New Theoretical Considerations In Polymer Rheology: Elastic Breakdown Of Chain Entanglement Network,
2014
University of Akron Main Campus
New Theoretical Considerations In Polymer Rheology: Elastic Breakdown Of Chain Entanglement Network, Shi-Qing Wang, Sham Ravindranath, Yangyang Wang, Pouyan Boukany
Shi-Qing Wang
Recent experimental evidence has motivated us to present a set of new theoretical considerations and to provide a rationale for interpreting the intriguing flow phenomena observed in entangled polymer solutions and melts [P. Tapadia and S. Q. Wang, Phys. Rev. Lett. 96, 016001 (2006); 96, 196001 (2006); S. Q. Wang , ibid. 97, 187801 (2006)]. Three forces have been recognized to play important roles in controlling the response of a strained entanglement network. During flow, an intermolecular locking force f(iml) arises and causes conformational deformation in each load-bearing strand between entanglements. The chain deformation builds up a retractive force f(retract) …
Large Amplitude Oscillatory Shear Behavior Of Entangled Polymer Solutions: Particle Tracking Velocimetric Investigation,
2014
University of Akron Main Campus
Large Amplitude Oscillatory Shear Behavior Of Entangled Polymer Solutions: Particle Tracking Velocimetric Investigation, Sham Ravindranath, Shi-Qing Wang
Shi-Qing Wang
Large amplitude oscillatory shear (LAOS) has been employed widely to probe the nonlinear behavior of complex fluids. Typically, the system undergoing LAOS has been assumed to experience homogeneous shear in each cycle so that material functions can be introduced to analyze the nonlinear dependence of these functions on the amplitude and frequency. Using particle-tracking velocimetric technique, we have carried a more systematic investigation on four different entangled polybutadiene (PBD) solutions with the number of entanglements per chain Z=13, 27, 64 and 119, extending well beyond the initial observations of shear banding in entangled PBD solutions under LAOS [Tapadia , Phys. …
Did Mineral Surface Chemistry And Toxicity Contribute To Evolution Of Microbial Extracellular Polymeric Substances?,
2014
University of Akron Main Campus
Did Mineral Surface Chemistry And Toxicity Contribute To Evolution Of Microbial Extracellular Polymeric Substances?, Jie Xu, Jay M. Campbell, Nianli Zhang, William J. Hickey, Nita Sahai
Nita Sahai
Modern ecological niches are teeming with an astonishing diversity of microbial life in biofilms closely associated with mineral surfaces, which highlights the remarkable success of microorganisms in conquering the challenges and capitalizing on the benefits presented by the mineral-water interface. Biofilm formation capability likely evolved on early Earth because biofilms provide crucial cell survival functions. The potential toxicity of mineral surfaces toward cells and the complexities of the mineral-water-cell interface in determining the toxicity mechanisms, however, have not been fully appreciated. Here, we report a previously unrecognized role for extracellular polymeric substances (EPS), which form biofilms in shielding cells against …
High-Temperature Fiber Matrices: Electrospinning And Rare-Earth Modification,
2014
University of Akron Main Campus
High-Temperature Fiber Matrices: Electrospinning And Rare-Earth Modification, W. Kataphinan, R. Teye-Mensah, E. Evans, R. Ramsier, Darrell Reneker
Darrell Hyson Reneker
We demonstrate the production of nonwoven mats of high-temperature organic and inorganic fibers by electrospinning. Specifically, glass/ceramic (tetraethylorthosilicate-SiO) and fire-blanket (polydiphenoxyphosphazene-PDPP) precursors are electrospun, and the resulting fibers are characterized by scanning electron microscopy, thermogravimetric analysis, and infrared (IR) spectroscopy. We find that the SiO fibers are smaller in diameter and more uniform than the PDPP fibers, and stable to higher temperatures. We also coat these fiber systems with several rare-earth nitrates, and find that these coatings can be used to selectively modify the near-IR spectra of the fibers. This work extends the use of electrospinning into two new classes …
Bending Instability In Electrospinning Of Nanofibers,
2014
University of Akron Main Campus
Bending Instability In Electrospinning Of Nanofibers, A. L. Yarin, S. Koombhongse, Darrell Hyson Reneker
Darrell Hyson Reneker
A localized approximation was developed to calculate the bending electric force acting on an electrified polymer jet, which is a key element of the electrospinning process for manufacturing of nanofibers. Using this force, a far reaching analogy between the electrically driven bending instability and the aerodynamically driven instability was established. Continuous, quasi-one-dimensional, partial differential equations were derived and used to predict the growth rate of small electrically driven bending perturbations of a liquid column. A discretized form of these equations, that accounts for solvent evaporation and polymer solidification, was used to calculate the jet paths during the course of nonlinear …
Motion Of Droplets Along Thin Fibers With Temperature Gradient,
2014
University of Akron Main Campus
Motion Of Droplets Along Thin Fibers With Temperature Gradient, Alexander L. Yarin, Wenxia Liu, Darrell Hyson Reneker
Darrell Hyson Reneker
Liquid n-decane, n-undecane, n-dodecane, and n-hexadecane formed tiny symmetrical droplets on a partially wettable cylindrical fiber. When a temperature gradient was created along the fiber, the droplets began to move along the fiber toward the cold region. An explanation of the phenomenon is related to the thermocapillary motion. Other possible mechanisms were ruled out. The theoretical results and experimental data agree reasonably well. (C) 2002 American Institute of Physics.
Poly(Meta-Phenylene Isophthalamide) Nanofibers: Coating And Post Processing,
2014
University of Akron Main Campus
Poly(Meta-Phenylene Isophthalamide) Nanofibers: Coating And Post Processing, Wenxia Liu, Mathew Graham, Edward Evans, Darrell Reneker
Darrell Hyson Reneker
Electrospun nanofibers have applications in the areas of filtration, composites; biomaterials, and electronics. Controlling the surface properties of these nanofibers is important for many applications. Nanofibers can also be used as unique substrates for observing the growth of deposited films and creating nanoscale structures. In this work, electrospun poly(meta-phenylene isophthalamide) (MPD-I) nanofibers were used as substrates for creating nanoscale structures out of carbon-based materials and metals. MPD-I was used because it can be electrospun into nanofibers with diameters smaller than 10 nm and it has good thermal stability. MPD-I nanofibers were coated with carbon, copper, and aluminum using plasma enhanced …
