Recycling and rheology of poly(lactic acid) (PLA) to make foams using supercritical fluid

Type of content
Journal Article
Thesis discipline
Degree name
Publisher
AIP Publishing
Journal Title
Journal ISSN
Volume Title
Language
en
Date
2021
Authors
Lin L
Lee Y
Park, Heon Ewan
Abstract

Biodegradable plastics are thought to be the possible directions in managing plastic pollutions. Unfortunately, they are not recycled in most countries since they are designed to decompose even though recycling is a more pragmatic method than landfill or incineration. Thus, it is more constructive to develop methods to recycle biodegradable plastics or to develop biodegradable yet recyclable plastics. In this study, we used cutlery with a composite of poly(lactic acid) (PLA) and talc. The possibility to recycle it to make foams was studied even though it will have lowered mechanical strength from the recycling process as it is less significant for this product. Tensile properties of solid PLA and foams showed no significant decrease in the strength up to three processes of compression molding and foaming. We performed shear rheometry to determine the thermal stability and dependences of the complex viscosity on frequency and temperature. The magnitude of the complex viscosity dramatically increased with decreasing frequency and such an upturn increased with temperature, but time-temperature superposition was valid at high temperatures. The extensional rheometry showed no strain hardening, but physical foaming using supercritical carbon dioxide (CO2) could still occur, and the operating conditions to obtain various foamed structures were determined. We also compared the effects of one-directional against three-dimensional expansion. Overall, the concentration of CO2 in PLA and crystallinity of the foams are the two key variables to describe the bulkiness of foams. Surprisingly, the lower the CO2 concentration, the bulkier the foams at any sorption temperature and pressure.

Description
Citation
Lin L, Lee Y, Park HE (2021). Recycling and rheology of poly(lactic acid) (PLA) to make foams using supercritical fluid. Physics of Fluids. 33(6). 067119-067119.
Keywords
Ngā upoko tukutuku/Māori subject headings
ANZSRC fields of research
01 Mathematical Sciences
02 Physical Sciences
09 Engineering
Fields of Research::40 - Engineering::4011 - Environmental engineering::401106 - Waste management, reduction, reuse and recycling
Fields of Research::40 - Engineering::4004 - Chemical engineering::400403 - Chemical engineering design
Fields of Research::40 - Engineering::4016 - Materials engineering::401609 - Polymers and plastics
Fields of Research::34 - Chemical sciences::3403 - Macromolecular and materials chemistry::340305 - Physical properties of materials
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