Repurposing Plastic Waste For Additive Manufacturing Feedstock: Development, 3D Printing And Characterization Of Sustainable Composites

Abstract

Plastic consumption has become a fundamental part of modern life, but its widespread use has led to alarming levels of waste generation. Global plastic production reached approximately 370 million tons in 2019 and is projected to rise to 900 million tons by 2050, contributing to severe environmental and health risks. Plastic pollution not only endangers wildlife and aquatic ecosystems but also poses carcinogenic and endocrine-disrupting threats to humans. Among various plastic types, polyethylene terephthalate (PET) significantly contributes to this crisis. Conventional recycling methods for PET often fall short of sustainability goals. However, additive manufacturing (AM), also known as 3D printing (3DP), presents a feasible pathway to repurpose recycled PET (rPET) into valuable, functional products. However, ensuring the preservation of rPET's mechanical and physical properties during the 3DP process remains a key challenge. This thesis focused on advancing sustainable additive manufacturing by utilizing rPET as viable printing material. To establish a foundation for this work, feedstock filaments were first prepared from post-consumer waste PET plastic bottles. With rPET feedstock in place, this thesis then explored the optimization of key 3DP parameters which are nozzle temperature, print temperature and print bed temperature to improve the dimensional and mechanical performance of rPET based prints. Additionally, a novel approach incorporating polyvinyl alcohol (PVA) powder as a filler in rPET filaments is investigated to enhance material performance in 3DP. The research identified optimal 3DP process parameters and demonstrated the viability of using rPET filaments for functional prototypes, contributing to sustainable manufacturing practices. Furthermore, this thesis highlighted the importance of reinforcements and precise control over 3DP conditions to maintain the mechanical strength of recycled polymers. Mechanical testing of rPET-PVA composite filaments, including tensile strength and stress-strain behavior, was conducted to assess their suitability for functional applications. The findings not only improve the reliability of rPET in AM but also emphasized the function of AM in promoting a circular economy by minimizing plastic waste and advancing sustainable production. Despite progress, prospective research is needed to resolve limitations in economic feasibility, long-term durability, and environmental impact, unlocking the full potential of recycled materials in 3DP.

Date of Award	2025
Original language	American English
Awarding Institution	HBKU College of Science and Engineering