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Articles 1 - 11 of 11
Full-Text Articles in Chemical Engineering
Evaluation Of Seal Integrity Of Flexible Food Polytrays By Destructive And Non-Destructive Techniques, William James Barlow Jr.
Evaluation Of Seal Integrity Of Flexible Food Polytrays By Destructive And Non-Destructive Techniques, William James Barlow Jr.
Masters Theses
The military has recently suffered a reduction in production capacity due to the rejection of their flexible food packaging. The rejection of these polytrays was due to sealing defects and the high standards set forth for the sealing quality. These standards set by the military were likely too conservative and until a test could be developed and optimized to quantitatively measure seal integrity, the standards will remain very high. The optimized test, whether destructive or non-destructive, must show that a particular defect, which might currently cause rejection, will not affect the quality of the items contained if passed as a …
Ordered Network Phases In Linear Poly(Isoprene-B-Styrene-B-Ethylene Oxide) Triblock Copolymers, Thomas H. Epps Iii, Eric W. Cochran, Travis S. Bailey, Ryan S. Waletzko, Cordell M. Hardy, Frank S. Bates
Ordered Network Phases In Linear Poly(Isoprene-B-Styrene-B-Ethylene Oxide) Triblock Copolymers, Thomas H. Epps Iii, Eric W. Cochran, Travis S. Bailey, Ryan S. Waletzko, Cordell M. Hardy, Frank S. Bates
Eric W. Cochran
The equilibrium phase behavior of 43 linear poly(isoprene-b-styrene-b- ethylene oxide) (ISO) triblock copolymer melts, with molecular weights that place these materials near the order-disorder transition, is reported. Ordered phase morphologies were characterized using small-angle X-ray scattering, transmission electron microscopy, dynamic mechanical spectroscopy, and static birefringence measurements. Interpretation of these results was aided by a modeling technique that facilitates resolution of reciprocal and real-space experimental data, leading to definitive three-dimensional morphological structures. Three distinct multiply continuous network morphologies are identified across a range of compositions between 0.1 ≤ f o ≤ 0.3, situated between two-domain and three-domain lamellae, where f o …
Statistical Mechanics Of Worm-Like Polymers From A New Generating Function, Gustavo A. Carri, Marcelo Marucho
Statistical Mechanics Of Worm-Like Polymers From A New Generating Function, Gustavo A. Carri, Marcelo Marucho
College of Polymer Science and Polymer Engineering
We present a mathematical approach to the worm-like chain model of semiflexible polymers. Our method is built on a novel generating function from which all the properties of the model can be derived. Moreover, this approach satisfies the local inextensibility constraint exactly. In this paper, we focus on the lowest order contribution to the generating function and derive explicit analytical expressions for the characteristic function, polymer propagator, single chain structure factor, and mean square end-to-end distance. These analytical expressions are valid for polymers with any degree of stiffness and contour length. We find that our calculations are able to capture …
Network Phases In Abc Triblock Copolymers, Thomas H. Epps Iii, Eric W. Cochran, Cordell M. Hardy, Travis S. Bailey, Ryan S. Waletzko, Frank S. Bates
Network Phases In Abc Triblock Copolymers, Thomas H. Epps Iii, Eric W. Cochran, Cordell M. Hardy, Travis S. Bailey, Ryan S. Waletzko, Frank S. Bates
Eric W. Cochran
Many naturally occurring and engineered products are influenced by network structures. Collagen networks provide a scaffold for living tissue, while swollen arrays of physically cross-linked polypeptides constitute gelatin, the familiar dessert and electrophoresis medium. Although the associated mesh sizes differ by several orders of magnitude, these examples share a common feature: three-dimensional connectivity that imparts mechanical rigidity. Intercalating additional interconnected components can yield broader functions, e.g., ionic or electrical conductivity, optical band gaps, and tailored heat and mass transfer.
Shear-Induced Network-To-Network Transition In A Block Copolymer Melt, Eric W. Cochran, Frank S. Bates
Shear-Induced Network-To-Network Transition In A Block Copolymer Melt, Eric W. Cochran, Frank S. Bates
Eric W. Cochran
The tricontinuous (10, 3)c shear-induced network-to-network transition in a block copolymer melt was analyzed using small-angle x-ray scattering. Investigations show that field-induced network-to-network phase transition was unprecedented in soft condensed matter. It was found that shear transforms were used for self-assembling the soft material into a single crystal (10, 3)d network. The results show the delicate nature of block copolymers phase behavior, where candidate morphologies were spaced closely together on the free energy surface.
Onset Of Tethered Chain Overcrowding, William Y. Chen, Joseph X. Zheng, Stephen Z. D. Cheng, Christopher Y. Li, Ping Huang, Huiming Xiong, Qing Ge, Ya Guo, Roderic P. Quirk, Bernard Lotz, Lingfeng Deng, Chi Wu, Edwin L. Thomas
Onset Of Tethered Chain Overcrowding, William Y. Chen, Joseph X. Zheng, Stephen Z. D. Cheng, Christopher Y. Li, Ping Huang, Huiming Xiong, Qing Ge, Ya Guo, Roderic P. Quirk, Bernard Lotz, Lingfeng Deng, Chi Wu, Edwin L. Thomas
College of Polymer Science and Polymer Engineering
We proposed an approach to precisely control the density of tethered chains on solid substrates using PEO-b-PS and PLLA-b-PS. As the crystallization temperature T-x increased, the PEO or PLLA lamellar crystal thickness d(L) increased as well as the reduced tethering density (σ) over tilde of the PS chains. The onset of tethered PS chains overcrowding in solution occurs at (σ) over tilde*similar to3.7-3.8 as evidenced by an abrupt change in the slope between (d(L))(-1) and T-x. This results from the extra surface free energy created by the tethered chain that starts to affect the growth barrier of the crystalline blocks.
Role Of Curvature Elasticity In Sectorization And Ripple Formation During Melt Crystallization Of Polymer Single Crystals, Rujul Mehta, Wirunya Keawwattana, Andrew L. Guenthner, Thein Kyu
Role Of Curvature Elasticity In Sectorization And Ripple Formation During Melt Crystallization Of Polymer Single Crystals, Rujul Mehta, Wirunya Keawwattana, Andrew L. Guenthner, Thein Kyu
College of Polymer Science and Polymer Engineering
The present article focuses on theoretical elucidation of possible effect of mechanical deformation on spatio-temporal emergence of unusual polymer morphology subjected to quiescent isothermal crystallization conditions. The present theory developed is based on a phase field model consisted of non-conserved time dependent Ginzburg-Landau equation having an asymmetric double well potential in the crystal order parameter signifying metastability for crystallization, coupled with the chain tilt angle involving curvature elasticity and strain recovery potentials. Under quiescent crystallization conditions, the curvature elasticity term is needed to discern the emergence of sectorized single crystals. Upon coupling with the strain recovery potential, the numerical calculation …
Modification Of Statistical Threading In Two-Component Pseudorotaxane Melts Using The Amphiphilic Approach And Variations In The Confinement Geometry, Sagar S. Rane, Wayne L. Mattice, Coleen Pugh
Modification Of Statistical Threading In Two-Component Pseudorotaxane Melts Using The Amphiphilic Approach And Variations In The Confinement Geometry, Sagar S. Rane, Wayne L. Mattice, Coleen Pugh
College of Polymer Science and Polymer Engineering
Recently we described a coarse-grained model of poly(ethylene oxide) and then employed that model to study the amount of spontaneous threading of cyclic molecules by linear chains in the melt [C. A. Helfer, G. Xu, W. L. Mattice, and C. Pugh, Macromolecules 36, 10071 (2003)]. Since the amount of statistical threading at equilibrium is small, there is interest in identifying physical changes in the system that will increase the threading. We now use that coarse-grained model to investigate the effect on threading of various hypothetical (but feasible) modifications to the two-component system of macrocycles and linear chains in the melt, …
Consequences Of Block Number On The Order-Disorder Transition And Viscoelastic Properties Of Linear (Ab)N Multiblock Copolymers, Lifeng Wu, Eric W. Cochran, Timothy P. Lodge, Frank S. Bates
Consequences Of Block Number On The Order-Disorder Transition And Viscoelastic Properties Of Linear (Ab)N Multiblock Copolymers, Lifeng Wu, Eric W. Cochran, Timothy P. Lodge, Frank S. Bates
Eric W. Cochran
The effect of block number on the order-disorder transition (ODT) and viscoelastic properties were studied for linear (AB) n multiblock copolymers. A series of symmetric poly(styrene-b-isoprene) n multiblocks ((SI) n, n = 1-10) were synthesized by anionic polymerization, and their order-disorder transition temperatures (T ODT) were located using dynamic mechanical spectroscopy. As n increases, T ODT approaches an asymptotic value, consistent with random phase approximation calculations. A systematic difference between the experimental and theoretical results is attributable to the effects of fluctuations, independent of the number of blocks. Addition of up to 20 vol % of a nonselective solvent depresses …
Growth Dynamics Of Isotactic Polypropylene Single Crystals During Isothermal Crystallization From A Miscible Polymeric Solvent, Rujul Mehta, Wirunya Keawwattana, Thein Kyu
Growth Dynamics Of Isotactic Polypropylene Single Crystals During Isothermal Crystallization From A Miscible Polymeric Solvent, Rujul Mehta, Wirunya Keawwattana, Thein Kyu
College of Polymer Science and Polymer Engineering
The present article presents a spatiotemporal growth of isotactic polypropylene (iPP) single crystals, melt crystallized from a polymeric solvent, i.e., poly (ethylene octene) copolymer that is known to be miscible with iPP. Optical and atomic force microscopic investigations reveal that the melt grown single crystals of iPP develop in the form of two parallel rows of crystal lamellae, but these crystals merge at the tips. To elucidate the mechanism of these emerging parallel rows of iPP crystals, a phase field model pertaining to solidification phenomena has been employed that involves a nonconserved crystal order parameter and a chain-tilting angle. This …
Environmentally-Friendly Physico-Chemical Rapid Ultrasonic Recycling Of Fumed Silica-Filled Poly(Dimethyl Siloxane) Vulcanizate, Sang Eun Shim, Victor V. Yashin, Avraam I. Isayev
Environmentally-Friendly Physico-Chemical Rapid Ultrasonic Recycling Of Fumed Silica-Filled Poly(Dimethyl Siloxane) Vulcanizate, Sang Eun Shim, Victor V. Yashin, Avraam I. Isayev
Avraam I Isayev
Fumed silica-filled PDMS, where quite a strong interaction exists between the filler and matrix via hydrogen bonding, was recycled by means of an extruder with high power ultrasound attachment. It was found that the reinforcing filler plays an important role in the devulcanization process. Compared to the precipitated silica-filled PDMS, higher power is consumed during the devulcanization process of fumed silica-filled PDMS due to a strong interaction between the fumed silica particles and PDMS chains. The decrease in crosslink density after the devulcanization process shows that the process is quite dependent on the concentration of fumed silica. Throughout a simulation …