Polymer Science Commons^™

Taylor Cone And Jetting From Liquid Droplets In Electrospinning Of Nanofibers, Alexander L. Yarin, S Koombhongse, Darrell Hyson Reneker

College of Polymer Science and Polymer Engineering

Sessile and pendant droplets of polymer solutions acquire stable shapes when they are electrically charged by applying an electrical potential difference between the droplet and a flat plate, if the potential is not too large. These stable shapes result only from equilibrium of the electric forces and surface tension in the cases of inviscid, Newtonian, and viscoelastic liquids. In liquids with a nonrelaxing elastic force, that force also affects the shapes. It is widely assumed that when the critical potential phi (0*) has been reached and any further increase will destroy the equilibrium, the liquid body acquires a conical shape …

Dislocation-Controlled Perforated Layer Phase In A Peo-B-Ps Diblock Copolymer, Lei Zhu, Ping Huang, Stephen Z. D. Cheng, Qing Ge, Roderic P. Quirk, Edwin L. Thomas, Bernard Lotz, Jean-Claude Wittmann, Benjamin S. Hsiao, Fengji Yeh, Lizhi Liu

College of Polymer Science and Polymer Engineering

Small angle x-ray analyses show that the shear-induced hexagonal perforated layer phase in a poly(ethylene oxide)-b-polystyrene diblock copolymer consists of trigonal (R3(overbar)m) twins and a hexagonal (P6(3)/mmc) structure, with trigonal twins being majority components. Transmission electron microscopy reveals that the hexagonal structure is generated through sequential intrinsic stacking faults on the second layer from a previous edge dislocation line, while the trigonal twins are formed by successive intrinsic stacking faults on neighboring layers due to the plastic deformation under mechanical shear.

Bending Instability In Electrospinning Of Nanofibers, A. L. Yarin, S. Koombhongse, Darrell Hyson Reneker

College of Polymer Science and Polymer Engineering

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 …

The Effects Of Incorporation Of Polyethylene Glycol On Properties Of Silica-Carbon Black-Filled Rubber Compound, Yoke Cheng Tang

Student Works (2000-2009)

The use of polyethylene glycol (PEG) to modify the surface of precipitated silica by means of physical adsorption was investigated. The effects of adding PEG on processing, cure and physical properties of a silica-carbon black-filled natural rubber truck tread compound were examined. For each series of investigation, two sets of experiments were conducted. Set I was to check the effects of both physical adsorption due to PEG and chemical modification due to a silane coupling agent, Si-69 on the surface of silica. Set 2 was to check the effects of physical adsorption due to PEG alone on the surface of …

Effects Of Compression Processing Parameters And Antioxidants On Molecular Degradation Of Biodegradable Poly-L-Lactide (Plla), Thomas J. Hannan Jr.

Masters Theses

The purpose of this research was to find a combination of poly (L-lactic acid), also known as poly-L-lactide or (PLLA) and antioxidants that would, together, produce a product whose degradation rate would be advantageous for use in biodegradable medical implants. Intrinsic viscosity tests were conducted on compression molded samples of PLLA that were molded at various processing parameters in order to find optimal parameters. The optimal processing parameters were found to be time 10 minutes, temperature 220°C, and pressure 1000 psi.

The molecular weight of PLLA sample was taken while pressure, time, and temperature were varied. As pressure increased, no …