Article ID Journal Published Year Pages File Type
6465125 Chemical Engineering Journal 2017 12 Pages PDF
Abstract

•Fully-biobased PLA foam was successfully obtained via easily scaled-up extrusion.•SC crystallites and dissolved gas synergistically promoted the crystallization of PLA.•Introduced SC crystallites endowed PLLA/PDLA foams with very high expansion ratio.•The obtained PLLA/PDLA foams exhibited smaller cell sizes and higher cell densities.

Success in the typical extrusion foaming process is always achieved by adding inorganic/organic fillers, which inevitably sacrifice poly(lactic acid) (PLA)'s green nature. Herein, we successfully fabricated well-defined cell structures of fully bio-based PLA foams using a series of asymmetric biodegradable poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) blends with small amounts of PDLA. We obtained large-scale PLLA/PDLA blends using a continuous melt compounding technique. The crystallization kinetics in the presence of dissolved carbon dioxide (CO2) under high pressures was investigated by using regular and high-pressure DSC. The PLA's crystallization rates were notably accelerated due to the significant synergy of the dissolved CO2 and the reserved SC crystallites. The continuous extrusion process, which could be easily scaled-up to industry, was used to fabricate the PLLA/PDLA blended foams. Using the neat PLLA foam, we successfully demonstrated how to make fully bio-based PLA foams with three orders of magnitude increased cell density, an enhanced expansion ratio over ten-fold, and increased crystallinity by 15%. Such a high cell density, a high expansion ratio and a high crystallinity are unprecedented in the continuous processing of fully green PLA foams. They possess great potential for use as a sustainable product in thermoformed food packaging applications.

Graphical abstractPLA crystallization rates were promoted due to the synergy of dissolved CO2 and reserved SC crystallites, which was favorable for the formation of fully bio-based PLA foams with much smaller cell sizes and high expansion ratio.Download high-res image (173KB)Download full-size image

Related Topics
Physical Sciences and Engineering Chemical Engineering Chemical Engineering (General)
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