| dc.description.abstract | Plastic waste and pollution have become a global environmental challenge due to their detrimental impacts on the environment, ecosystems, and human health. Since 1950s, plastic waste, particularly single-use plastics, has been accumulating in landfills, oceans, and other natural habitats, leading to a range of environmental problems. With the growing awareness on the plastic pollution, biodegradable plastics, with the advantages of high degradability, non-toxic end products and low cost, have been regarded as an ideal alternative of conventional plastics. Biodegradable materials, such as those derived from plants, cellulose, and starch, exhibit the capability of undergoing degradation by microorganisms or within composting environments over a relatively brief period. In recent years, there has been a notable increase in the market share of biodegradable materials, and projections indicate that this trend is expected to continue over the coming decades. Polylactic acid (PLA) is widely recognized as one of the most prevalent biodegradable polymers owing to its advantageous properties such as high hardness, exceptional strength, and cost-effectiveness. Consequently, PLA finds extensive utilization across diverse fields, including medical and packaging applications. While the biodegradable plastics can be degraded within months when the specific conditions are met, including optimal temperature, appropriate humidity levels, and an environment abundant in microorganisms, it could take them two years or longer to decay in an open environment.
Many studies have provided the evidence that biodegradable materials are hard to degrade in two years period, which means the fragmentation and broken apart could occur during the degradation, therefore leading to the release of microplastics (MPs) and other microparticles-
A great number of studies have found that large number of MPs additive microparticles and other impurities could be released from plastic wastes and daily used plastic products. As the results, MPs are ubiquitous in the environment. The presence of MPs in the environment, including in water bodies, soil, and even in the air, has raised concerns about their potential impacts on human health and the environment.
While biodegradable materials exhibit considerable resistance to degradation within a two-year timeframe, the fragmentation and disintegration processes during their degradation could lead to the release of MPs and other microparticles. In fact, there has been an increased emphasis on the potential MPs release from biodegradable plastics and their associated risks on the public health and the environment.
In this study, PLA was taken as the example to conduct the biodegradable plastic research. Firstly, a comprehensive review was conducted to summarize the category, properties and characterization, the additive addition as well as the ecological risk of the biodegradable plastic. Afterwards, a systematic method of determining the plastic-released microparticles (PMPs), including MPs and other microparticles, released from PLA products was developed by simulating the daily use protocol, which can be applied on the determination of various plastic products. Subsequently, the polyethylene (PE) and PLA single-used paper cups were selected as the experiment objects to compare the PMPs release from biodegradable material with the conventional plastic products. This study found that the PMPs from biodegradable cups were 4.2 times higher than that of conventional paper cups, including MPs and other additives. Sequentially, four different forms of PLA material were selected to evaluate the PMPs release impact factor and degradation behavior under alkaline condition. The results indicated that the mechanical stress was the main factor leading to the particle release, while the addition of functional chemical additives caused different degradation degrees. Finally, a lab-scale mitigation method was developed by coating a layer of copper oxide (CuO) film on 3D printed PLA sheet. The CuO can provide a reduction rate of 66.7% on PMPs release. In parallel, a 9-week weathering experiment was conducted and the results showed that the CuO coating still displayed a PMPs release reduction of 36.7%. Furthermore, the CuO coating does not affect the biodegradability of PLA sheet, which is an effective and practical method to apply on the PMPs mitigation research of biodegradable polymers. This study conducted a comprehensive investigation into biodegradable materials, specifically focusing on whether biodegradable plastics, particularly PLA, can serve as environmentally friendly materials in the future. However, the findings of this study suggest that further research and careful consideration are necessary to determine the true environmental viability of biodegradable plastics. | en |
