Date of Publication
11-2025
Document Type
Master's Thesis
Degree Name
Master of Science in Applied Physics
Subject Categories
Physics
College
College of Science
Department/Unit
Physics
Thesis Advisor
Edgar A. Vallar
Defense Panel Chair
Maria Cecilia D. Galvez
Defense Panel Member
Tatsuo Shiina
Prane Mariel B. Ong
Abstract (English)
Existing studies currently monitor plastic litter degradation, leading to increased environmental microplastic problems. Traditional methods of monitoring polymer degradation are often destructive, slow, and limited to laboratory settings. This study introduces an application of a Mie-scattering Lidar system using a 405 nm pulsed laser diode as a non-contact method to remotely detect surface changes in five common plastics: polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and high-density polyethylene (HDPE). A low-cost atmospheric cold plasma (ACP) system was developed to induce controlled surface modifications. Lidar signals were measured from 20 × 20 mm samples exposed for 0, 5, and 10 minutes at 10–20 m distances. The Lidar backscattering coefficient and peak intensities consistently declined with increasing plasma exposure, indicating progressive degradation. Validation with scanning electron microscopy (SEM) and atomic force microscopy (AFM) confirmed surface roughening and morphological alterations. At the same time, Fourier Transform infrared spectroscopy (FTIR) spectra indicated oxidative bond scission and chemical modification. Contact angle analysis showed significant reductions in hydrophobicity, up to 61° for PP, reflecting increased surface wettability, while weight loss analyses revealed modest but measurable bulk degradation. ANOVA confirmed significant differences across treatments, and Pearson correlation showed strong associations between Lidar signals and contact angle (r > 0.9 for PP, PVC, HDPE). Regression models established Lidar’s predictive ability for surface characterization. Overall, this study demonstrates the potential of compact Mie-scattering Lidar as a real-time, non-contact, and scalable method for detecting early plastic degradation. By correlating optical backscatter with conventional characterization techniques, Lidar emerges as a practical early-warning tool for monitoring plastic fragmentation and mitigating the formation of microplastics in the environment.
Abstract Format
html
Abstract (Filipino)
Kasalukuyang sinusubaybayan ng mga umiiral na pag-aaral ang pagkasira ng mga basurang plastik na nagdudulot ng pagdami ng mikroplastik sa kapaligiran. Ang mga tradisyonal na pamamaraan ng pagsubaybay sa degradasyon ng polimer ay kadalasang mapanira (destructive), mabagal, at limitado lamang sa loob ng laboratoryo. Ipinakikilala ng pag-aaral na ito ang aplikasyon ng Mie-scattering Lidar system gamit ang 405 nm pulsed laser diode bilang isang di-kontak at remote na paraan upang matukoy ang mga pagbabago sa ibabaw ng limang uri ng karaniwang plastik: polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), at high-density polyethylene (HDPE).
Bumuo ng isang low-cost atmospheric cold plasma (ACP) system upang magsagawa ng kontroladong pagbabago sa ibabaw ng mga plastik. Sinukat ang Lidar signals mula sa mga sample na 20 × 20 mm na in-expose sa loob ng 0, 5, at 10 minuto mula sa 10–20 metrong distansya. Ang Lidar backscattering coefficient at peak intensities ay tuluy-tuloy na bumaba habang tumataas ang oras ng plasma exposure, indikasyon ng progresibong degradasyon. Kinumpirma ng scanning electron microscopy (SEM) at atomic force microscopy (AFM) ang pagbuo ng gaspang at pagbabago sa morpolohiya ng ibabaw. Samantala, ipinakita ng Fourier Transform Infrared Spectroscopy (FTIR) ang pagkakaroon ng oksidatibong bond scission at kemikal na pagbabago. Nagpakita ang contact angle analysis ng makabuluhang pagbaba ng hydrophobicity—umabot hanggang 61° para sa PP—na nagpapahiwatig ng pagtaas ng wettability. Ipinakita naman ng weight loss analysis ang bahagya ngunit nasusukat na pagbabago sa kabuuang mass. Kumpirmado rin ng ANOVA ang makabuluhang pagkakaiba sa bawat treatment, habang ipinakita ng Pearson correlation ang malalakas na ugnayan ng Lidar signals at contact angle (r > 0.9 para sa PP, PVC, HDPE). Itinatag ng regression models ang kakayahan ng Lidar sa predictive surface characterization.
Sa kabuuan, ipinapakita ng pag-aaral na ito ang potensyal ng compact Mie-scattering Lidar bilang isang real-time, non-contact, at scalable na pamamaraan para maagang matukoy ang pagkasira ng plastik. Sa pamamagitan ng pag-uugnay ng optical backscatter sa mga tradisyunal na teknik ng karakterisasyon, lumilitaw ang Lidar bilang isang praktikal na early-warning tool para sa pagsubaybay ng fragmentation ng plastik at pag-iwas sa patuloy na pagdami ng mikroplastik sa kapaligiran.
Abstract Format
html
Language
English
Format
Electronic
Keywords
Optical radar; Mie scattering; Plastics—Biodegradation
Recommended Citation
Tabafa, M. H. (2025). Detection and surface characterization of plasma-treated plastics using a compact 405 nm laser diode mie lidar systems. Retrieved from https://animorepository.dlsu.edu.ph/etdm_physics/27
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Embargo Period
12-12-2028
