Browsing by Author "Samuel M. Hudson, Committee Member"

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Formation of Beta-Cyclodextrin Inclusion Complex with a Phenolic Antioxidant and its Industrial Applications in Polyethylene Film
(2009-07-25) Agrawal, Manisha; Alan E. Tonelli, Committee Co-Chair; Hyun Suk Whang, Committee Co-Chair; Samuel M. Hudson, Committee Member; C. M. Balik, Committee Member
AGRAWAL, MANISHA. Formation of [beta]-Cyclodextrin Inclusion Complex with a Phenolic Antioxidant and its Industrial Applications in Polyethylene Film. (Under the guidance of Dr. Hyun Suk Whang) Butylated hydroxytoluene (BHT) is a phenolic antioxidant, which is primarily used in food additives. Due to its high volatility, it can be suspected to have losses through volatilization in high temperature applications. However, there is barely any research work focused on the formation of BHT-[beta]-CD-IC. In this study, we have successfully formed the inclusion compound between BHT and [beta]-CD (BHT-[beta]-CD-IC) and characterized it using wide-angle x-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), nuclear magnetic resonance spectroscopy (NMR) and ultra violet visible spectroscopy (UV-Vis). We produced on pilot scale three sets of low density polyethylene (LDPE) films with the addition of BHT, [beta]-CD, and BHT-[beta]-CD-IC. The determination of BHT content in the films was carried out using Gas Chromatography- Mass Spectrometry (GC-MS). The results show that 44% BHT was lost from BHT-[beta]-CD-IC LDPE films while 78% BHT was lost from the BHT LDPE film. Hence, the complex proved to be more efficient in preventing loss of BHT due to encapsulation of volatile guest. In addition, microscopy studies indicate that BHT-[beta]-CD-IC LDPE film shows small aggregates uniformly distributed over a large range in the LDPE matrix. The oxidative performance of the films was studied using differential scanning calorimetry (DSC) for determining the oxidation induction time (OITtime) and oxidation induction temperature (OITtemp.). It was found that OITtemp.method is less sensitive as compared to the OITtime method. The OITtime was 35 min for the BHT-[beta]-CD-IC LDPE film as compared with 16 min and 26 min values of LDPE and BHT LDPE films, respectively. Hence, the encapsulation of BHT in the CD maximizes the efficiency and stability to thermal degradation for BHT-[beta]-CD-IC film. The viscoelastic behavior of the films was also studied using dynamic mechanical analysis (DMA). The results indicate increase in storage modulus (El) and loss modulus of the complex (Ell). Also, the maxima of tan delta (Ell/El) for LDPE films processed with BHT, [beta]-CD and BHT-[beta]-CD-IC are shifted to lower temperature. Further, a migration study of BHT from the complex using food stimulant, which is underway, will give an insight on the controlled release of active component in the film. This may open a great potential for industrial applications of CD-ICs.
Platinum and Platinum Alloy-Carbon Nanofiber Composites for Use as Electrodes in Direct Methanol Fuel Cells
(2010-04-20) Lin, Zhan; Xiangwu Zhang, Committee Chair; Wendy E. Krause, Committee Co-Chair; Saad A. Khan, Committee Member; Samuel M. Hudson, Committee Member
In response to the energy needs of modern society and emerging ecological concerns, the pursuit of novel, low-cost, and environmentally friendly energy conversion and storage systems has raised significant interest. Among various energy conversion and storage systems, fuel cells have become a primary research focus since they convert chemical energy directly into electrical energy with high efficiency and low pollutant emissions. For example, direct methanol fuel cells (DMFCs), which supply the electrical energy by converting methanol to energy, are an ideal fuel cell system for applications in electric vehicles and electronic portable devices due to their relatively quick start-up, rapid response to catalyst loading, and low operating temperature. However, the wide commercial use of DMFCs in advanced hybrid electric vehicles and electronic portable devices is hampered by their high cost, poor durability, and relatively low energy and power densities. In order to address these problems, their research focuses on the development of highly active electrode catalysts coupled with a suitable electrode structure for the oxidation of methanol at the anode and the reduction of oxygen at the cathode to attain high efficiency of DMFCs, and subsequently lowering the cost. In this dissertation, the fabrication of novel platinum and platinum alloy nanoparticle-loaded carbon nanofibers (CNFs) for use as electrodes in DMFCs is demonstrated through electrospinning, carbonization, and deposition. The resulting CNF-based electrodes possess the properties of high electroactive surface area, good catalytic abilities towards the oxidation of methanol and the reduction of oxygen, and great long-time stability. As a result, DMFCs using these CNFs-supported platinum and platinum alloy nanoparticles as electrodes offer many advantages, such as improved electrocatalytic abilities, long-term stability, easy fabrication, low cost, and environmental benignity. Therefore, this new technology opens up new opportunities to develop high-performance electrode materials in the future for high-performance DMFCs, which are one of the promising power sources for consumer devices and electric vehicles, and play a critical role in solving the worldwide critical energy issue.
Preventing Strength Loss of Unbleached Kraft Fibers
(2003-10-30) Zhang, Min; Samuel M. Hudson, Committee Member; Richard A. Venditti, Committee Co-Chair; John A. Heitmann, Committee Member; Martin A. Hubbe, Committee Chair
The purpose of this study was to understand the mechanism of paper strength loss that occurs when paper made from chemical pulps is recycled. It is found that due to drying, unbleached kraft pine fibers lost cellulose viscosity, water retention value, fiber flexibility and accessible surface area. Handsheets made from dried fibers had lower paper strength and lower apparent density compared to corresponding primary handsheets made from never-dried fibers. With the increase in drying temperature of virgin fibers, the above properties of dried fibers and recycled handsheets experienced larger effects. It was hypothesized that adding certain chemicals to virgin fibers before drying could prevent strength loss upon recycling. Results showed that relatively low molecular weight additives (such as sucrose and glucose) appeared to interfere with the mechanism of pore closure during drying and improved the strength of recycled paper. Higher molecular weight chemicals added to never dried virgin fibers (such as starch) also increased the strength of the recycled paper but this was attributed to residual chemical being retained on the fiber surface during recycling. Although the effect of adding certain chemicals to virgin fibers before drying could significantly prevent strength loss in recycled paper, it was determined that improvements of recycled paper strength due to refining were of much larger magnitude. It is found that recycled handsheets had lower paper strength compared with virgin handsheets at all pH values considered during paper formation within the range of pH 3 to pH 8. There was no significant effect of pH on paper strength within this range. The fiber flexibility tests showed that the method is useful to determine the flexibility of individual fibers. In the case of sugar treatment, treated fibers showed higher flexibility compared to untreated fibers after drying, and glucose was found to have larger effect than sucrose. With respect to papermaking conditions, fibers were more flexible under alkaline conditions than fibers under acidic conditions, but fibers became less flexible with increasing salt concentration and hardness.