UNT Libraries - 29 Matching Results

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Mineral-filled polypropylene: Improvement of scratch resistance

Description: A potential alternative to acrylonitrile-butadiene-styrene (ABS) and polycarbonate+ABS (PC+ABS), pigmented mineral-filled polypropylene (PP) finds an opening in automotive interior components such as instrument panels, knee bolsters, consoles, etc. Because of the lack of surface aesthetics, pigmented mineral-filled PP is experiencing a limitation to its acceptance in many applications. This study focuses on exploring various mineral fillers and additives in polypropylene to provide a material with enhanced scratch resistance. Several physical properties including Rockwell and Shore D hardness are investigated, and it is determined that Filler W improves scratch resistance. It is also determined that Filler T-filled-PP has poor scratch resistance even with the addition of a lubricant.
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Date: December 2001
Creator: Khatib, Jamal F.

Techniques Utilized in the Characterization of Existing Materials for Improved Material Development

Description: It has become increasingly important to remain on the cutting edge of technology for a company to remain competitive and survive in today's high-tech industries. To do this, a company needs various resources dedicated to this cause. One of these resources is the use of existing materials, as starting points, for which improved materials can be based. For this, a company must rely on the characterization of existing materials to bring that base technology into their company. Through this evaluation, the base materials properties can be obtained and a material with improved properties can be developed. There are many techniques that can be used in characterizing an existing material, but not every technique is required to obtain the desired goal. The techniques utilized depend upon the depth of identification required. This report summarizes several techniques utilized in the characterization of existing materials and provides some examples of evaluated products.
Date: December 2001
Creator: Withaeger, Gary

Polyamide-imide and Montmorillonite Nanocomposites

Description: Solvent suspensions of a high performance polymer, Polyamide-imide (PAI) are widely used in magnetic wire coatings. Here we investigate the effect that the introduction of montmorillonite (MMT) has on PAI. MMT was introduced into an uncured PAI suspension; the sample was then cured by step-wise heat treatment. Polarized optical microscopy was used to choose the best suitable MMT for PAI matrix and to study the distribution of MMT in PAI matrix. Concentration dependent dispersion effect was studied by x-ray diffraction (XRD) and was confirmed by Transmission electron microscopy (TEM). Differential scanning Calorimetry (DSC) and Thermogravimetric analysis (TGA) was used to study impact of MMT on glass transition temperature (Tg) and degradation properties of PAI respectively. Micro-hardness testing of PAI nanocomposites was also performed. A concentration dependent state of dispersion was obtained. The glass transition (Tg), degradation and mechanical properties were found to correlate to the state of dispersion.
Date: August 2001
Creator: Ranade, Ajit

Thermal, Electrical, and Structural Analysis of Graphite Foam

Description: A graphite foam was developed at Oak Ridge National Laboratory (ORNL) by Dr. James Klett and license was granted to POCO Graphite, Inc. to manufacture and market the product as PocoFoam™. Unlike many processes currently used to manufacture carbon foams, this process yields a highly graphitic structure and overcomes many limitations, such as oxidation stabilization, that are routinely encountered in the development of carbon foam materials. The structure, thermal properties, electrical resistivity, isotropy, and density uniformity of PocoFoam™ were evaluated. These properties and characteristics of PocoFoam™ are compared with natural and synthetic graphite in order to show that, albeit similar, it is unique. Thermal diffusivity and thermal conductivity were derived from Fourier's energy equation. It was determined that PocoFoam™ has the equivalent thermal conductivity of metals routinely used as heat sinks and that thermal diffusivity is as much as four times greater than pure copper and pure aluminum. SEM and XRD results indicate that PocoFoam™ has a high degree of crystalline alignment and near theoretical d spacing that is more typical of natural flake graphite than synthetic graphite. PocoFoam™ is anisotropic, indicating an isotropy factor of 0.5, and may yield higher thermal conductivity at cryogenic temperatures than is observed in polycrystalline graphite.
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Date: August 2001
Creator: Morgan, Dwayne Russell

Epoxy + Liquid Crystalline Epoxy Coreacted Networks

Description: Molecular reinforcement through in-situ polymerization of liquid crystalline epoxies (LCEs) and a non-liquid crystalline epoxy has been investigated. Three LCEs: diglycidyl ether of 4,4'-dihydroxybiphenol (DGE-DHBP) and digylcidyl ether of 4-hydroxyphenyl-4"-hydroxybiphenyl-4'-carboxylate (DGE-HHC), were synthesized and blended with diglycidyl ether of bisphenol F (DGEBP-F) and subsequently cured with anhydride and amine curing agents. Curing kinetics were determined using differential scanning calorimetry (DSC). Parameters for autocatalytic curing kinetics of both pure monomers and blended systems were determined. The extent of cure for both monomers was monitored by using Fourier transform infrared spectroscopy (FT-IR). The glass transitions were evaluated as a function of composition using DSC and dynamic mechanical analysis (DMA). The results show that the LC constituent affects the curing kinetics of the epoxy resin and that the systems are highly miscible. The effects of molecular reinforcement of DGEBP-F by DGE-DHBP and DGE-HHC were investigated. The concentration of the liquid crystalline moiety affects mechanical properties. Tensile, impact and fracture toughness tests results are evaluated. Scanning electron microscopy of the fracture surfaces shows changes in failure mechanisms compared to the pure components. Results indicate that mechanical properties of the blended samples are improved already at low concentration by weight of the LCE added into epoxy resin. The improvement in mechanical properties was found to occur irrespective of the absence of liquid crystallinity in the blended networks. The mechanism of crack study indicates that crack deflection and crack bridging are the mechanisms in case of LC epoxy. In case of LC modified epoxy, the crack deflection is the main mechanism. Moreover, the effect of coreacting an epoxy with a reactive monomer liquid crystalline epoxy as a matrix for glass fiber composites was investigated. Mechanical properties of the modified matrix were determined by tensile, flexural and impact testing. The improvement in toughness of the bulk matrix ...
Date: December 2000
Creator: Punchaipetch, Prakaipetch

Preparation and Characterization of a Treated Montmorillonite Clay and Epoxy Nanocomposite

Description: Montmorillonite reinforced polymers are a new development in the area of nanocomposite materials. Since reinforcement of epoxy is important to the development of high strength adhesives and composite matrices, the introduction of montmorillonite to epoxy is of interest. Compositional effects on epoxy reactivity, on molecular relaxation, and on mechanical properties were investigated. Change in reactivity was determined by Differential Scanning Calorimetry. Tensile properties at room temperature indicated improved modulus and retention of strength of the epoxy matrix but a decreased elongation to failure. Depression of dry nanocomposite glass transition was observed for nanocomposites beyond 5% by weight montmorillonite. Samples that were saturated with water showed lower moduli due to the epoxy matrix. The greatest moisture absorption rate was found at 7%, the least at 3%.
Date: December 2000
Creator: Butzloff, Peter Robert

Cure Kinetics and Processing Parameters of Neat and Reinforced High Performance Epoxy Resins: Evaluation of Techniques

Description: Kinetic equation parameters for the curing reaction of a commercial glass fiber reinforced high performance epoxy prepreg composed of the tetrafunctional epoxy tetraglycidyl 4,4-diaminodiphenyl methane (TGDDM), the tetrafunctional amine curing agent 4,4’-diaminodiphenylsulfone (DDS) and an ionic initiator/accelerator, are determined by various thermal analysis techniques and the results compared. The reaction is monitored by heat generated determined by differential scanning calorimetry (DSC). The changes in physical properties indicating increasing conversion are followed by shifts in glass transition temperature determined by DSC and temperature-modulated DSC (TMDSC), thermomechanical (TMA) and dynamic mechanical (DMA) analysis and thermally stimulated depolarization (TSD). Changes in viscosity, also indicative of degree of conversion, are monitored by DMA. Thermal stability as a function of degree of cure is monitored by thermogravimetric analysis (TGA). The parameters of the general kinetic equations, including activation energy and rate constant, are explained and used to compare results of various techniques. The utilities of the kinetic descriptions are demonstrated in the construction of a useful time-temperature-transformation (TTT) diagram for rapid determination of processing parameters in the processing of prepregs. Copyright is held by the author, unless otherwise noted. All rights reserved. Files: Thesis.pdf Special Conditions
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Date: December 1999
Creator: Bilyeu, Bryan

Analyses of Particulate Contaminants in Semiconductor Processing Fluids

Description: Particle contamination control is a critical issue for the semiconductor industry. In the near future, this industry will be concerned with the chemical identities of contaminant particles as small as 0.01 pm in size. Therefore, analytical techniques with both high chemical sensitivity and spatial resolution are required. Transmission electron microscopy (TEM) provides excellent spatial resolution and yields structural and compositional information. It is rarely used, however, due to the difficulty of sample preparation. The goals of this research are to promote the use of TEM as an ultrafine particle analysis tool by developing new sample preparation methods, and to exploit the new TEM techniques for analysis of particles in semiconductor processing fluids. A TEM methodology for the analysis of particulate contaminants in fluids with an elemental detectability limit as low as 0.1 part per trillion (ppt), and a particle concentration detectability limit as low as 1 particle/ml for particles greater than 0.2 pm was developed and successfully applied to the analysis of particles in HF, H202, de-ionized (DI) water, and on the surface of an electronic device. HF samples from three manufacturers were examined. For HF (B), the maximum particle concentration was 8.3 x 103 particles/ml. Both a viscous material and lath-shaped particles were observed. The Sb concentration was less than 0.6 part per billion (ppb). HF (C) was the cleanest. CaF2 and TiO2 particles were identified in HF (D). For H2 02, iron and tin oxides and hydroxides were identified. The maximum particle concentration was 990 particles/ml. The Sn and Fe concentrations were less than 0.3 ppb. Spherical and dendritic particles were observed. For DI water, spherical and dendritic particles (<2 particles/ml), and particles containing Fe or Si with concentrations less than 0.1 ppt were observed. Contaminants on an electronic device surface were also analyzed. Clusters of small particles ...
Date: August 1998
Creator: Xu, Daxue

Analysis of Thermoplastic Polyimide + Polymer Liquid Crystal Blends

Description: Thermoplastic polyimides (TPIs) exhibit high glass transition temperatures (Tgs), which make them useful in high performance applications. Amorphous and semicrystalline TPIs show sub-Tg relaxations, which can aid in improving strength characteristics through energy absorption. The a relaxation of both types of TPIs indicates a cooperative nature. The semicrystalline TPI shows thermo-irreversible cold crystallization phenomenon. The polymer liquid crystal (PLC) used in the blends is thermotropic and with longitudinal molecular structure. The small heat capacity change (ACP) associated with the glass transition indicates the PLC to be rigid rod in nature. The PLC shows a small endotherm associated with the melting. The addition of PLC to the semicrystalline TPI does not significantly affect the Tg or the melting point (Tm). The cold crystallization temperature (Tc) increases with the addition of the PLC, indicating channeling phenomenon. The addition of PLC also causes a negative deviation of the ACP, which is another evidence for channeling. The TPI, PLC and their blends show high thermal stability. The semicrystalline TPI absorbs moisture; this effect decreases with the addition of the PLC. The absorbed moisture does not show any effect on the degradation. The addition of PLC beyond 30 wt.% does not result in an improvement of properties. The amorphous TPI + PLC blends also show the negative deviation of ACP from linearity with composition. The addition of PLC causes a decrease in the thermal conductivity in the transverse direction to the PLC orientation. The thermomechanical analysis indicates isotropic expansivity for the amorphous TPI and a small anisotropy for the semicrystalline TPI. The PLC shows large anisotropy in expansivity. Even 5 wt. % concentration of PLC in the blend induces considerable anisotropy in the expansivity. Thus, blends show controllable expansivity through PLC concentration. Amorphous TPI + PLC blends also show excellent film formability. The amorphous TPI ...
Date: May 1998
Creator: Gopalanarayanan, Bhaskar