ORCID

Abstract

Coordinated deployment of thermally protected unmanned aerial vehicles (UAVs)equipped for active firefighting operations around incidents such as the GrenfellTower fire could have provided substantial support to life-saving efforts. Incurrent practice, UAVs employed in comparable emergencies are largelyconfined to observational and surveillance roles, thereby substantiallyunderutilising their potential. Expanding their use to direct firefighting tasksrequires the integration of advanced thermal protection systems capable ofwithstanding significantly elevated temperatures associated with carbonaceousfire plumes. In particular, the development of a lightweight thermal barrier coatingthat adheres reliably to fused deposition modelled (FDM) polymers, such aspolylactic acid (GTP), is critical for operational viability and the minimisation ofthe UAV’s all up weight (AUW). A central technical challenge addressed in thiswork arises from the intrinsic thermal limitations of FDM polymers, whose glasstransition region and crystalline melting point constrain its mechanicalperformance under severe thermal loading.This study examines the application of a lightweight silicon dioxide (SiO₂) basedthermal barrier coating onto a FDM polymer component and evaluates itsinfluence on the polymer’s tensile and thermal properties. Exploiting silicon’smarked reduction in thermal conductivity when exposed to increasingtemperatures, the central research question is whether such a coating can formvian amorphous thermal protective barrier on an FDM polymer substrate whilepreserving its tensile integrity and geometry. A substantial disparity infundamental thermal characteristics between silicon and FDM polymers requiredtargeted approaches to achieve effective amalgamation of the two materials. Byharnessing a tightly focused laser beam in combination with the low thermalconductivity of selected polymers, an amorphous surface coating was producedfrom a silicon dioxide–metal oxide powder which was dispersed in distilled wateras the application medium. The substantial localised thermal input andaccompanying laser ablation motivated an investigation into the effects ofpost-processing heat treatments on 3D printed polymer substrates, employingtwo novel approaches based on autoclave and microwave exposure-printedpolymer substrates, employing two novel approaches based on autoclave andmicrowave exposure. Two biobased polymers were examined: (i) ahigh-performance, sustainable filament (Green TEC Pro, GTP), proposed as analternative to conventional engineering polymers such as PC, ABS and PEEK,and (ii) a biobased, isosorbide-based polycarbonate resin designed to combinekey characteristics of PC and PMMA. Both materials exhibit high stiffness andflexural strength, together with elevated functional heat resistance. GTP has afunctional heat resistance up to 110°�� to 120°��. Durabio has a lower functionalheat resistance between 80°�� to 90°��. Both are suitable for structuralapplications under a thermal load. The GTP specimens demonstrated a markedincrease in tensile strength following combined heat treatment and laser ablation,relative to the non-heat-treated reference specimens, indicating that theproposed processing route can enhance the mechanical performance ofadditively manufactured bio-based polymers.viiThe initial silicon dioxide coating underwent thermal testing; however, the resultswere inconclusive because the coating exhibited surface fissures and, in someregions, poor adhesion to the substrate. To address these deficiencies, aninvestigation was conducted into improving the coating by modifying theapplication medium. Using sucrose dissolved to saturation in distilled water wasfound to significantly reduce the incidence of fissures in the coating.

Awarding Institution(s)

University of Plymouth

Supervisor

John Summerscales, Jasper Graham-Jones, Asiya Khan

Document Type

Thesis

Publication Date

2026

Deposit Date

June 2026

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