Author Type

Graduate Student

Date of Award

Summer 7-16-2026

Document Type

Dissertation

Publication Status

Version of Record

Submission Date

July 2026

Department

Ocean and Mechanical Engineering

College Granting Degree

College of Engineering and Computer Science

Department Granting Degree

Ocean and Mechanical Engineering

Degree Name

Doctor of Philosophy (PhD)

Thesis/Dissertation Advisor [Chair]

Hassan Mahfuz

Abstract

Thermoplastic copolyester elastomers (TPEEs) are widely used in engineering applications because of their flexibility, toughness, and chemical resistance. However, prolonged exposure to marine environments can reduce their mechanical performance through moisture-induced degradation. This research investigated the use of titanium dioxide (TiO2) nanoparticles and APTES-functionalized TiO2 nanoparticles to improve the mechanical, thermal, and environmental durability of Hytrel 5556. Nanocomposites containing 1 wt.% and 2 wt.% TiO2 were fabricated through melt blending and compression molding. Mechanical properties were evaluated through tensile, compression, flexural, and impact testing, while thermal behavior was characterized using differential scanning calorimetry (DSC). Nanoparticle dispersion was examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Hydrothermal aging was conducted in heated saltwater to simulate subsea service conditions. FTIR analysis confirmed successful APTES functionalization through the formation of Si–O–Ti and Si–O–Si bonds on the nanoparticle surface. TiO2 reinforcement improved tensile, compressive, flexural, and impact performance while reducing moisture uptake during hydrothermal aging. APTES functionalization vi further enhanced nanoparticle–matrix interactions, resulting in substantial improvements in impact resistance, flexural strength, and flexural modulus. The 2 wt.% APTES-TiO2 nanocomposite achieved an impact resistance of 553 kJ/m2 and a flexural modulus of 244 MPa, representing increases of approximately 54% and 28%, respectively, compared with neat Hytrel. Functionalized nanocomposites also exhibited excellent property retention after hydrothermal aging. These results demonstrate that APTES-functionalized TiO2 nanoparticles significantly enhance the mechanical performance and environmental durability of Hytrel-based nanocomposites for marine and offshore applications.

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