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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.


Okoro, TASIE B 28 September 2013 (has links)
In laser transmission welding (LTW), a laser beam passes through the laser-transparent part and is absorbed by carbon black (CB) in the laser-absorbent part. This causes a temperature rise at the interface between the parts which leads to melting, diffusion and ultimately joining of the two components. Weld temperatures increase with laser power at a given scan speed. However at higher temperatures, it has been observed that weld strength of LTW starts to decline due to material thermal degradation. Thermal degradation of materials is a kinetic phenomenon which depends on both temperature and time. Therefore there is no specific temperature for thermal degradation. Thermal gravimetric analysis (TGA) is used to study the thermal degradation of two commonly used thermoplastic materials: polycarbonate (PC) and polyamide 6 (PA6). Each material was studied at two levels of CB. It is shown in this work that increasing the carbon black (CB) level from 0.05 to 0.2wt% has no significant effect on the thermal stability of PA6. However, it is observed that increasing the CB level from 0.05 to 0.2wt% has a noticeable effect on the thermal stability of PC. The TGA data were then used to obtain the kinetic triplets (frequency factor (k_0), activation energy (E), and reaction model (f(α))) of the materials using a non-linear model-fitting method. These kinetic triplets were combined with temperature-time data obtained from a Finite Element Method (FEM) simulation of the LTW process to predict material degradation during LTW. The predicted degradation was then compared with experimental data. It is found that the predicted onset of material degradation is in good agreement with experimentally observed thermal degradation (of both visually observed degradation onset and weld strength decline) for PC and PA6. A semi-empirical model based on the FEM temperature data is also developed in this work as a simpler alternative for obtaining LTW maximum temperature-time profiles for prediction of material thermal degradation during LTW. Comparison of the predicted material conversion using temperature-time profile obtained by FEM and the semi-empirical model shows good agreement. / Thesis (Master, Chemical Engineering) -- Queen's University, 2013-09-27 10:45:24.688

Injection molding of thermoplastics in rectangular cavities

Doan, Phung Hien January 1974 (has links)
No description available.

Characterisation of some dendritic polymers, copolymers, blends and nanocomposites

Wang, Haipeng, 1968- January 2002 (has links)
Abstract not available

Strain rate sensitivity index of thermoplastics from variable strain rate and stress relaxation testing

Goble, David Leroy 29 April 1991 (has links)
Graduation date: 1991

Consolidation of thermoplastic powder-coated towpreg / Consolidation of thermoplastic power-coated towpreg

Bradley, Jurron 12 1900 (has links)
No description available.

Processing characteristics and properites [sic] of glass fiber reinforced composites from post consumer carpets

Jin, Kun, January 2003 (has links) (PDF)
Thesis (M.S. in Poly.)--School of Textile and Fiber Engineering, Georgia Institute of Technology, 2004. Directed by Youjiang Wang. / Includes bibliographical references (leaves [66-67]).

Intensive mixing of thermoplastic polymers in uni-rotor systems

Hyatt, Harry James, 1937- January 1961 (has links)
No description available.

Modification of poly(ethylene terephthalate) through thermal and photochemical crosslinking

Jones, Jeffrey R. 08 1900 (has links)
No description available.

Development of a guarded hot plate thermal conductivity measuring apparatus for thermoplastic materials

Jackson, Kenneth Wade 08 1900 (has links)
No description available.

Injection molding of thermoplastics.

Kenig, Samuel January 1972 (has links)
No description available.

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