All ETDs from UAB

Advisory Committee Chair

Brian S Pillay

Advisory Committee Members

Derrick Dean

Haibin Ning

Uday Vaidya

Peter Walsh

Mark Weaver

Document Type

Dissertation

Date of Award

2014

Degree Name by School

Doctor of Philosophy (PhD) School of Engineering

Abstract

The in-situ polymerization process of anionic polyamide-6 (APA-6) presents the opportunity for a new class of composite materials with excellent performance and wide applicability in the automotive, energy, transportation, and aerospace industries. Despite the inherent advantages of the process, industrial adoption is virtually nonexistent. The following work advances the APA-6 process in three distinct ways. First, the applicability of graphite-based nanoparticles to improve the processability and final performance of the material was evaluated. Nanographite platelets (NGPs) were selectively incorporated into a woven glass fiber/APA-6 laminate via a spraying technique. The polymerization kinetics were unaffected by the presence of NGPs. Mechanical properties were largely unaffected by NGPs except the matrix-dominated laminate short-beam strength which was increased by 25.6 % with a 0.5 wt. % NGP concentration. Second, an alternative chemical process enabling a "single stream" infusion strategy was demonstrated which could greatly improve the automation of the APA-6 process. A soluble diisocyanate initiator (SDI) was synthesized and deposited onto woven glass fabric. A composite laminate was successfully produced using a single, inert solution of monomer and activator. However, an initiator wash-out problem was identified in the process. Surface-initiated polymerization of APA-6 was successfully demonstrated using a specialized silane sizing that contained APA-6 initiation chemistry. iv Finally, nanographite oxide platelets (NGOPs) were produced using a planetary ball-milling process from graphite flake and carbon dioxide. A kinetic model was applied to optimize the ball-mill design for simultaneous nanographite exfoliation and carboxylation. The ball-mill was shown to be capable of producing NGOPs with lateral dimensions of < 1 um and thicknesses << 1 um. A reaction to functionalize the NGOPs with 4,4'-methylene diphenyl diisocyanate (MDI) and epsilon-caprolactam was tested and characterized. Although the presence of diisocyanate-based initiation species was inferred via Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA), the reaction between the isocyanate and the carboxyl groups was not verified. The FNGPs were unable to initiate surface polymerization of APA-6, possibly due to steric hindrance of the initiator adsorbed to the FNGP surfaces.

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