5th Annual Student Colloquium

Wednesday, October 15, 2008

Louisville, Kentucky

Download the Call for Abstracts - EXTENDED Deadline September 2, 2008

(Oral Presentation PowerPoint due September 26, 2008.)

  

Keynote Speaker

8:00-9:00 AM - TBD

Student Oral Presentations

#1 - 9:00 AM - "High Temperature Elastomer/Clay Nanocomposites for Oilfield Applications" by Sriram Lakshminarayanan, Dr. Uttandaraman Sundararaj and Dr. K. Nandakumar of the University of Alberta

Layered silicate polymer nanocomposites have gained great importance in the recent years because they can greatly improve properties of polymers, much more significantly than fillers used in conventional composites. In this research, elastomer/clay nanocomposites were made from high temperature elastomers for potential utilization in Progressive Cavity Pumps (PCPs). PCPs are used as an artificial lift method to pump oil from several thousand feet depths to the surface. The integral components of a PCP are the stator, which is usually made of elastomer, and a rotor, usually made of metal. The pumps are exposed to severe conditions during operation and the elastomer has to withstand the high temperatures, high solids content, high viscous dissipation, etc. PCP's currently cannot be used for higher temperature oil production because these temperature levels are not accessible using hydrocarbon elastomers.

In this presentation, mechanical properties and other relevant properties of these high temperature elastomer nanocomposites will be compared with carbon black composites containing the same curing system. In addition, hybrid compounds, with both carbon black and nanoclay will be analyzed and their results reported. Rheological characterization was performed on these materials and the results were analyzed to understand the micro-/nano-structure.

 

#2 - 9:30 AM - "Strengthening of Polyolefins by Bottom-up Self-assemlby of POSS Nanoparticles" by Byoung Jo Lee and Dr. Sadhan C. Jana of the University of Akron

It is known that molecules of polyhedral oligomeric silsesquioxane (POSS) can self-assemble into spherical, fibrillar, or lamellar nanoparticles by bottom-up self assembly process while mixing with a host polymer. This study capitalizes on such nanoparticle formation to increase the melt strength and tensile properties of polyolefins and polyolefin fibers. We found that melt-mixing of POSS with polyolefins does not produce desired results due to poor compatibility between most POSS molecules and polyolefins. Therefore, a novel method was developed whereby mixtures of nucleating agents and POSS were mixed with polyolefins. Nucleating agents having higher compatibility with POSS aid its dispersion and provide templates for self-assembly of POSS molecules into nanoparticles of 25-200 nm. A typical polypropylene (PP) formulation contains 0.3 wt% clarifying agent and 5-10 wt% POSS. These materials can be spun into fibers with close to 68% reduction in diameter and offer 40- 50% increase in modulus and 45-55% increase in tensile strength compared to unfilled PP.

 

#3 - 10:00 AM - "Elastomeric Compounds Degradation in Drinking Water Distribution Systems" by Raja Mohan Nagisetty, Dr. Thomas D. Rockaway, Dr. Gerald A. Willing and Dr. Richard M. Higashi of the University of Louisville

Due to the increasing health concerns and USEPA regulations over the last decade, chloramines have preferentially been used in place of chlorine as disinfectant. After this change, some utilities have reported high elastomeric compound failure rates in their water systems. To predict the long-term performance of elastomers within the water systems, accelerated degradation experiments were conducted at the combinations of three temperatures (23^oC, 45^oC and 70^oC) and three chloramine concentrations (1-, 30-, and 60 mg/L concentrations) for natural rubber, neoprene rubber, ethylene propylene diene monomer (peroxide-cured), ethylene propylene diene monomer (sulfur-cured), styrene butadiene rubber, and nitrile rubber. Elastomer degradation was characterized by mass change, volume change, breaking stress, breaking strain and hardness. Using a time-temperature superposition (TTS) principle the accelerated test results were doubly-shifted (temperature and chloramine concentration) to service conditions to generate long-term performance curves. TTS technique was not suitable for swelling data, hence, performance curves for swelling were developed using diffusion theory. Also, the possible leaching of organic compounds due to this elastomer degradation into drinking waters has been investigated using Solid Phase Micro Extraction and Gas Chromatography/ Mass Spectrometry.

 

#4 - 10:30 AM - "Interface Area Function for Investigation of Swelling Behavior and Young's Modulus of Nanocomposites" by Mithun Bhattacharya and Prof. Anil K. Bhowmick of the Indian Institute of Technology, Kharagpur

Polymer-filler interaction for nanocomposites was quantified by introducing Interface Area Function (IAF), to account for the nanofiller characteristics comprising of the specific surface area, correlation length and the filler volume fraction. IAF supplants the immeasurable filler characteristic terms, rendering tractability to the equation derived by considering the restraining forces acting on a nanofiller- elliptical platelet- embedded in polymer matrix. However, neglecting such terms reduces the same to the Kraus's equation. Recognition of the due importance of such filler characteristics, by introduction of IAF, resulted in better fitment of swelling data and also conformance with the trend predicted by Zisman's interpretation of surface energy. Experimental values of Young's modulus of natural and styrene-butadiene rubber nanocomposites and those predicted by Guth-Gold and Halpin-Tsai equations for composites conform post-introduction of IAF, with mere 5-20% deviations. The accurate fitment of the resulting constitutive equations indicates suitable integration of the shape and aggregate effects.

 

#5 - 11:00 AM - "The Mechanics of Frictional Sliding at the Elastomer/Rigid Surface Interface" by Philip Gabriel, Dr. James Busfield and Prof. Alan Thomas of The University of London

It is widely accepted that there are two principal factors commonly considered to give rise to a frictional force during the sliding of a rigid surface on a flexible elastomer. The first being due to the work of adhesion at the interface; the second to the viscoelastic energy required to deform the rubber materials. A finite element analysis (FEA) investigation into the mechanics of rubber friction is reported here. An additional third geometric factor is identified that relates just to the deformation of the rubber can also contribute to the frictional force. This entirely geometric contribution under certain conditions increases the frictional force considerably above that expected from a consideration of the interfacial friction coefficient alone. This will therefore make a significant contribution to many every day frictional sliding applications such as tyres on a road surface. This contribution is dependent on the depth of penetration of the rigid surface into the elastomer and is therefore perhaps comparable to the frictional behaviour found when wrapping a rope around a capstan.

 

#6 - 11:30 AM - "Ultrasonic Treatment of PEN/LCP Blends During Extrusion" by Kaan Gunes and Dr. A. I. Isayev of the University of Akron

Ultrasonic extrusion of blends of wholly aromatic liquid crystalline polymer (LCP) and polyethylene naphthalate (PEN) was studied. Rheological, thermal, mechanical and morphological characterization of the blends was performed. The viscosity of untreated PEN was greater than the viscosity of untreated LCP, while viscosity of the untreated blends varied with composition. Blends became shear thinning with increasing LCP content. PEN treated at high ultrasonic amplitudes showed lower viscosity and Tg, indicating degradation under action of ultrasound. Untreated PEN/LCP blends became substantially stronger and stiffer with addition of LCP, while the elongation at yield and impact strength decreased. Improvements were recorded in the Young's modulus, tensile strength and impact strength of 90/10 PEN/LCP blends with treatment at an ultrasonic amplitude of 7.5 mm. In situ created LCP nanosize fibrils in the skin region, and LCP droplets in the core region were observed in injection moldings of PEN/LCP blends. Improvements in interfacial adhesion between the LCP and PEN phases with ultrasonic treatment were observed through SEM pictures. The size of LCP droplets and fibrils increased with treatment at an ultrasonic amplitude of 10 mm due to the lower viscosity of treated PEN. The latter led to reduced mechanical properties of blends. The effect of adding a transesterification catalyst, tetrabutyl orthotitanate (TBOT), to 80/20 PEN/LCP blends was also studied without and with ultrasonic treatment during extrusion.

 

#7 - 1:30 PM - "Visco-Elastic Behavior of Rubber in a Combined Torsion-Tension Test" by Nutthanun Suphadon, Dr. James Busfield and Prof. Alan Thomas of the University of London

If a rubber rod is subjected to a simple extension of extension ratio and then either twisted or excited by small strain oscillations in the direction of the pre-extension, it is possible to measure the anisotropy in the visco-elastic behaviour induced by the pre-extension. Previous work has found that tan dropped with increasing extension which was interpreted as lowering of internal viscosity due to chain orientation. These experiments present further work on rubber materials under dynamic loading and confirm the general finding of decreasing tan with increasing extension. However, we believe that the results can be understood in terms of changes to the test piece geometry alone. The assumption we propose is that under conditions of a small torsional or tension oscillation superimposed on a large static tensile deformation, the fundamental dissipative process is itself little affected by moderate static strains that are insufficient to cause substantial orientation of the monomer units in a chain. This seem reasonable, as up to 100% strain the statistical theory of rubber like elasticity suggests that the amount of orientation should not be substantial for moderately crosslinked rubber. In torsion therefore, the energy dissipation will depend on the strained dimensions of the rubber cylinder and the square of amplitude of the small strained produced by torsion alone. This theory is supported by the experimental observations.

 

#8 - 2:00 PM - "High Temperature Nanoindentation of Neat Resins and Carbon Composites of PMR-15 Polyimide" by David C. Jones, Dr. Y. Charles Lu and Dr. Greg A. Schoeppner with the University of Kentucky and Wright Patterson Air Force Base

This paper presents the high temperature nanoindentation experiments performed on neat resins and unidirectional carbon fiber composites of the well-studied aerospace polymer, PMR-15 polyimide. A sharp-tipped Berkovich nanoindenter equipped with hot-stage heating system was used. The creep deformation is observed to occur during nanoindentation of polymers and can affect the determinations of contact stiffness, elastic modulus and hardness. Experimental methods on minimizing the creep effect are proposed; analytical procedure for considering creep deformation is also given. The temperature dependent mechanical properties of PMR-15 are successfully measured and results indicate that the present high temperature nanoindentation technique is reliable for quantitative characterizations of local material properties at elevated temperatures. A study of the carbon composite follows, and presents previously unstudied behavior of the local material properties in the interfacial region at high temperature in-situ conditions.

 

#9 - 2:30 PM - "Synthesis and Characterization of Maleic Anhydride-Grafted Engage®/Dimethyldioctadecyl Quaternary Ammonium Chloride-Modified Montmorillonite Clay Nanocomposites" by Ganesh Latta, Dr. Wei-Ping Pan and Quentin Lineberry with Western Kentucky University

Maleic anhydride (MA) was grafted onto ethylene octene copolymer (Engage®) via radical initiation. The MA grafted Engage (MA-g-Engage) was characterized by FTIR and XPS. The nanocomposites of MA-g-Engage with an organically modified (dimethyldioctadecyl quaternary ammonium chloride) montmorillonite (M-MMT) were synthesized using a solution intercalation technique. The intercalation of M-MMT was verified by the shift of the X-ray diffraction peak to a lower angle. The internal structure and dispersion state of the M-MMT in the nanocomposites were observed by a transmission electron microscope, which confirmed that the clay was in the intercalated state. Below the glass transition temperature, the storage modulus of MA-g-Engage was higher than the neat Engage. The non-oxidative thermal degradation temperatures of MA-g-Engage and MA-g-Engage/M-MMT nanocomposite were higher than the neat Engage.

 

#10 - 3:00 PM - "Identification of the Composition and Growth of In Vitro Natural Rubber using High Resolution Size Exclusion Chromatography" by Cheng Ching K. Chiang, Dr. Judit E. Puskas, Colleen McMahan, and Wenshuang Xie with The University of Akron and the United States Department of Agriculture

Recently, Puskas et al. have proposed that the molecular mechanism of natural rubber (NR) biosynthesis is through carbocationic polymerization. To acquire further insight into the mechanism, in vitro NR biosynthesis experiments were performed at the United States Department of Agriculture (USDA) with combinations of enzymatically active rubber particles from H. brasiliensis,(RRIM600), isopentenyl diphosphate (IPP), farnesyl diphosphate (FPP), and metal cofactor (Mg2+). In this study, high resolution Size Exclusion Chromatography (SEC) was used to decipher the distribution of polyisoprenoids and oligoisoprenoids of rubber particles to monitor the growth of in vitro natural rubber.

 

#11 - 3:30 PM - TBD - RESERVED FOR UNDERGRADUATE PRESENTER

 

#12 - 4:00 PM - TBD - RESERVED FOR UNDERGRADUATE PRESENTER

 

#13 - 4:30 PM - TBD - RESERVED FOR UNDERGRADUATE PRESENTER

Student Poster Presentations

#1 - "Cut Growth in Natural Rubber Vulcanizates" by Meng Cai and Dr. Gary Hamed of the University of Akron

Every solid body contains inevitable flaws of various shapes and sizes. When a solid is subjected to a global stress, the local stresses at the tips of these flaws are magnified and can exceed the mean applied stress, and then fracture begins. Griffith¹ proposed and energy balance criterion for the fracture of an elastic solid. He postulated that a crack will grow a distance if the elastic energy released by the growth is greater than the surface free energy of the surfaces thus created. However, this criterion is not applicable to rubber. When a crack grows, irreversible processes occur in the vicinity of the tip, leading to energy dissipation that must be made up from the available elastic energy

The research presented investigated the mechanical properties and reinforcement mechanisms of natural rubber (NR) vulcanizates reinforced with carbon black. For both gum and black-filled natural rubber, reversion was lowest by adding intermediate multifunctional acrylate ester as anit-reversion coagent. Tensile tests of the precut NR were carried out. The vulcanizates structure has been examined by cure rheometry, ATR-FTIR and miscroscopy.

References: 1. A. A. Griffith, VI. The Phenomena of Rupture and Flow in Solids, Phil. Trans. Roy. Soc. Lond., 1920, A221, 163

 

#2 - "Synthesis of a Polyisobutylene-farnesyl Pyrophosphate Macroinitiator for In-vitro Synthesis of Polyisobutylene-b-cis-1,4-polyisprene" by Cheng Ching "Kurt" Chiang, Dr. Judit E. Puskas and Dr. Chrys Wesdemiotis of The University of Akron

Research in biochemistry revealed that the biosynthesis of polyisoprenoids and terpenes proceeds through cationic polymerization. Recently, Puskas et al. proposed that natural rubber (cis-1,4 polyisoprene, NR) biosynthesis also proceeds via a carbocationic mechanism.¹ To develop better understanding of this process, a synthetic macroinitiator analogue of nature's initiator, farnesyl pyrophosphate (FPP), will be employed in an in vitro NR biosynthesis system to synthesize PIB-block-NR in vitro, in collaboration with the United States Department of Agriculture (USDA). This work discusses the first four steps of the synthesis of the polyisobutylene-farnesyl pyrophosphate (PIB-FPP) macroinitiator. The structures of the macroinitiator and its intermediates were confirmed by nuclear magnetic resonance (NMR) spectroscopy and matrix-assisted laser desorption/ionization - time of flight (MALDI-TOF) mass spectroscopy.

References: 1. Puskas, J. E.; Gautriaud, E.; Deffieux, A.; Kennedy, J. P. Progress in Polymer Science 2006, 31, 533-548.

 

#3 - "Effect of Structural Stiffness on Fragility of Polymers: A Qualitative Picture" by Kumar Kunal and Dr. Alexei P. Sokolov of the University of Akron

Glass transition in polymeric liquids is accompanied by strongly non-Arrhenius temperature variations of segmental relaxation time . The deviations of from Arrhenius behavior is described by the fragility parameter, where is the glass transition temperature. It appears that most polymers are very fragile compared to small molecular weight liquids, the reasons for which remain unclear. We have studied the segmental dynamics of various polymers using dielectric spectroscopy and dynamic mechanical analysis. Our analysis reveals that the relative stiffness of side groups relative to the backbone is an important parameter that controls fragility. This approach suggests that the high fragility of seemingly flexible-backbone polymers such as polydimethysiloxane may be a result of the high relative stiffness of the side groups compared to the backbone - a characteristic that distinguishes it from similar structures with comparably stiff side groups and backbone with extremely low fragility, such as polyisobutylene. We have also studied the fast dynamics of several polymers using Raman and Brillouin spectroscopy in order to understand how these fast motions correlate with the much slower segmental dynamics.

 

#4 - "Experimental Investigation and Constitutive Modeling of the Large Deformation Mechanical Behavior of Filled Elastomers" by Aparajita Bhattacharya, Dr. James M. Caruthers and Dr. Grigori Medvedev of Purdue Universtiy

The stress-strain response of vulcanized carbon black filled rubber during loading/unloading has been studied as a function of temperature, filler content and filler properties such as structure and particle size. At low temperature, R, which is the ratio of the instantaneous modulus on unloading to that during loading at the beginning of unloading, increases significantly. Lowering temperature also lead to an increase in the hysterisis observed during the first loading/unloading cycle. Cyclic loading/unloading and Mullins experiments have been performed on materials containing 5 phr to 50 phr of carbon black. The filler structures range from DBPA numbers of 40 ml/100g to 620 ml/100g and their particle sizes from 25 nm to 250 nm. At a given filler content, structure is found to have a very small effect on R. A dramatic effect on R is observed for fillers having the same structure but varying particle sizes, where R increases with decrease in particle size. The amount of filler affects the hysterisis as well as R, and a distinct increase in R is observed at filler content in the range of percolation threshold. Stress relaxation experiments were used to characterize the mobility of the material at various points in the deformation history. The dependence of relaxation times on stress-strain, temperature are filler properties are presented.

 

#5 - "Synthesis of Arborescent Polystyrenes via an Inimer-Type Reversible Addition- Fragmentation Chain Transfer (RAFT) Polymerization" by Andrew J. Heidenreich and Dr. Judit E. Puskas of The University of Akron

High molecular weight polymers of randomly branched (dendritic or arborescent) architecture have unique physical and rheological properties. We believe that the unique properties of natural rubber may be due to such architecture. Dendritic rubbers have proven to be difficult to synthesize in an industrially viable manner. The Puskas group successfully synthesized high molecular weight polyisobutylenes using the polymerization concept called the inimer (initiator-monomer) method. Our goal is to extend this concept to a controlled free radical polymerization process called Reversible Addition-Fragmentation Chain Transfer (RAFT) to develop a one-pot method of synthesizing dendritic polyisoprene, SBR and other rubbers. This work describes the RAFT copolymerization of styrene. The number-average molecular weight (M_n) of the polymers was much higher than theoretically calculated for a linear polymerization, which suggests that a high degree of branching is occur. The average number of branches per molecule (B) was calculated. The polymerization retained the controlled behavior associated with typical RAFT polymerizations. This study shows the potential or this type of polymerization in synthesizing rubbers of arborescent architecture.