Date of Award

12-2014

Document Type

Thesis

Degree Name

Master of Science in Mechanical Engineering (MSME)

Department

Mechanical Engineering

First Advisor

Dr. Yousef Haik

Second Advisor

Dr. Ahmed Alawar

Abstract

The central goal of this thesis is to produce electrically conductive nanocomposites made out of carbon black obtained from waste tires as filler into a polymeric matrix. Waste tires are discarded in substantial numbers on a daily basis, posing a significant environmental concern. By weight, about 25-35% of a tire is carbon black. Pyrolysis is a convenient and environmental friendly process to produce carbon black from tires. Due to carbon black’s low density, high electrical conductivity and economic feasibility, this thesis investigates the electrical conductivity of nanocomposites that utilizes carbon black particles as fillers. As a result of its modified and controllable properties, composites with fillers present a radical alternative to conventional polymers and their blends. The small size of the fillers leads to exceptional large interfacial area in the composites. The interface controls the degree of the interaction between the filler and the polymer thus controlling the properties.

The effect of annealing temperature (550°C-1250°C) on the electrical properties of carbon black obtained from tires was investigated. Generally, the DC electrical conductivity improved when the annealing temperature increased. The modulation of the electrical conductivity as a function of annealing temperatures was explored using Raman spectroscopy, Energy dispersive X-ray, Scanning electron microscopy, X-Ray diffraction and thermo-gravimetric analysis. Annealed carbon black was used as filler in a polymeric matrix. The annealed waste carbon black was blended into epoxy at different wt. % to investigate the electrical conductivity, Furthermore, annealed carbon black was used as a filler in a Carbon Fiber Reinforced Polymer (CFRP) and then the effect of different percentage of waste carbon black was studied. After that, through plane electrical conductivity, surface electrical conductivity, through plane thermal conductivity and flexural strength were examined.

The results showed that the electrical conductivity for the annealed carbon black at 1250°C was improved to a value 40 σ/cm. Furthermore, impregnating a high amount of annealed carbon black (40 wt. %) in a polymeric matrix resulted in a low electrical conductivity of 0.0034 σ/cm.

Blending annealed carbon black into carbon fiber reinforced polymer (CFRP) resulted in alternating the electrical conductivity of the composite material. The surface conductivity of carbon fiber polymer was 2.5 σ (per share). However, the surface conductivity of impregnating 2 wt. % annealed waste carbon black into CFRP was 13 σ (per square). The results also showed that addition of 5 wt. % of waste carbon black noticeably decreased the area specific resistance of CFRP from 199 to 98 mΩ.cm2. The through-plane thermal conductivity of CFRP increased as carbon black wt. % increased. The through-plane thermal conductivity increased by 78% when the waste carbon black loading reached 16 wt. %. However, loading the composite with waste carbon black resulted in decreasing the flexural strength.

It is recommended to blend 5 wt. % of waste carbon black annealed at 1250°C into CFRP to provide enhancement in both the through-plane and surface electrical conductivity. The surface conductivity was enhanced by 80% when blending 5 wt. % of waste carbon black. The through plane resistivity reduced 51% by adding 5 wt. % of waste carbon black.

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