Dissertation/ Thesis
Lifetime and Degradation Studies of Poly (Methyl Methacrylate) (PMMA) via Data-driven Methods
| العنوان: | Lifetime and Degradation Studies of Poly (Methyl Methacrylate) (PMMA) via Data-driven Methods |
|---|---|
| المؤلفون: | Li, Donghui |
| بيانات النشر: | Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. |
| سنة النشر: | 2020 |
| المجموعة: | Ohiolink ETDs |
| Original Material: | http://rave.ohiolink.edu/etdc/view?acc_num=case1586535156011492 |
| مصطلحات موضوعية: | Polymer Chemistry, Materials Science, Optical Properties, Polymer Degradation, Data Science, PMMA and Self-Organizing Map |
| الوصف: | Poly(methyl methacrylate), also know as acrylic, has excellent optical properties, light weight, good mechanical properties, and weatherability.Due to the balance of these outstanding properties with cost efficiency, poly(methyl methacrylate)s are widely used in architecture, medicine, electronics, agriculture, paints, aircraft, and automotive industries.However, the lifetime of poly(methyl methacrylate)(PMMA) is reduced in outdoor applications because of exposure to solar radiation, temperature, and moisture.During the polymer degradation process, a variety of environmental stressors act on the polymer leading to degradation of its properties.Although standardized durability and weathering tests are widely used to collect failure information and evaluate durability of materials based on the typical pass/fail criteria, degradation modes, mechanisms, and rates are not clearly understood.Therefore, a better understanding of degradation modes, mechanisms, and rates is critical.To optimize and extend the service life of polymer materials to more than 25 years in the outdoor environment, a domain knowledge-based and data-driven approach has been utilized to quantitatively investigate the temporal evolution of degradation modes, mechanisms and rates under various stepwise exposure conditions.Six grades of PMMA were studied, including one unstabilized and five stabilized PMMAs exposed 3200 hours in three weathering conditions.The unstabilized PMMA showed a significant YI increase of over 25, whereas a highly-stabilized PMMA showed a slight YI increase only between 0.5 to 0.7.The degradation of unstabilized acrylic, revealed by Urbach edge analysis, arises from the presence of residual MMA monomer, with a shift of absorption edge from 4.35 eV to 3.11 eV under UVA-340 irradiation.For unstabilized and partially-stabilized PMMA formulations, quantitative degradation rates (the Induced absorbance to dose (IAD)) indicates that the UVA-340 irradiation (Hot QUV) shows 3-6 times higher degradation rate than the full spectrum exposure (Q-SUN).Photobleaching and photodarkening were both observed during the degradation of the UV-stabilized formulation.Degradation pathway models of unstabilized and partially-stabilized in the (Stressor|Mechanism|Response) framework both demonstrate that IAD275, the tracking variable for the fundamental absorption edge of PMMA, has a strong relationship with both UV dose (Adjusted R2=0.82-0.94) and YI (Adjusted R2=0.87-0.99).Use of self-organizing map analysis on UV fluorescence data detected that there are 3 different degradation categories: unstabilized, partially-stabilized, and highly-stabilized, each with characteristic behaviors. |
| Original Identifier: | oai:etd.ohiolink.edu:case1586535156011492 |
| نوع الوثيقة: | Text |
| اللغة: | English |
| الاتاحة: | http://rave.ohiolink.edu/etdc/view?acc_num=case1586535156011492 |
| Rights: | unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws. |
| رقم الانضمام: | edsndl.OhioLink.oai.etd.ohiolink.edu.case1586535156011492 |
| قاعدة البيانات: | Networked Digital Library of Theses & Dissertations |
| الوصف غير متاح. |