Towards a circular economy for chemically strengthened glass: Mechanochemical degradation and advanced remanufacturing

Abstract

Current limitations in the transition toward a Circular Economy (CE) for high-value chemically strengthened glasses (CSGs), particularly alkali-boroaluminosilicates utilized in consumer electronics, are attributed to a deficiency in restorative strategies and significant technical barriers in machining. The present work investigates the weathering-induced degradation of CSG and establishes a validated remanufacturing pathway through optimized Spark Assisted Chemical Engraving (SACE). Initially, the investigation addresses the systemic gap in glass waste management by proposing a conceptual assessment model that utilizes artificial intelligence-driven inspection and internet of things-based lifecycle tracking to evaluate the degradation state of end-of-life glass and assign its optimum recovery level. The fundamental scientific basis of this study analyzes the complex environmental responses of CSG through accelerated weathering phases. A comparative time-dependent study identifies a fundamental mechanochemical divergence where native boroaluminosilicate glass adheres to a gel densification model, while CSG follows a network depolymerization model. Because chemical strengthening induces structural modifications that weaken the local glass network, the resulting CSG matrix faces severe hydrolytic instability within immediate surface atomic layers. Consequently, environmental weathering facilitates rapid leaching of alkali ions, generating a chemically loose and porous hydrogel alteration layer on the glass surface. Subsequent mapping of synergistic interactions between temperature, humidity, UV radiation, and time reveals a smoother but hazier paradox. Hydrothermal interactions topologically smooth the CSG surface through preferential asperity dissolution following Ostwald-Freundlich kinetics, while simultaneously inducing optical haze in the UV and blue spectrum through Rayleigh scattering within a protonated nano-porous alteration layer typically less than 50 nm thick. Crucially, this research applies linear elastic fracture mechanics to verify a kinetic shielding effect, demonstrating that the compressive stress profile at a depth of approximately 40 μm effectively neutralizes the stress intensity of superficial weathering flaws. Experimental results confirm that macroscopic mechanical reliability, including scratch hardness and scratch resistance critical load, remains entirely invariant despite detectable optical degradation. Following bulk integrity verification, the present work establishes a statistically validated process window for high-quality freeform machining of Corning Gorilla Glass 3 (GG3) using SACE. By optimizing voltage, tool speed, and alkaline electrolyte concentration, the proposed methodology successfully bypasses catastrophic brittle fracture and thermal damage in toughened substrates, achieving an edge chipping threshold below 5 μm. In summary, the current research provides a robust scientific basis for assessing the functional viability of weathered CSG and delivers the manufacturing methodology required to implement a closed-loop CE framework for end-of-life (EoL), high-value glass sheets. These findings transform EoL CSG from a municipal liability into a valuable feedstock for high-tech remanufacturing.

Date	10 Aug 2026
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Lucas Hof (Supervisor)