Increased expansion ratio, cell density, and compression strength of microcellular poly(lactic acid) foams via lignin graft poly(lactic acid) as a biobased nucleating agent

Abstract

Green and renewable foaming poly(lactic acid) (PLA) represents one of the promising developments in PLA materials. This study is the first to use the lignin graft PLA copolymer (LG‐g‐PLA) to improve the foamability of PLA as a biobased nucleating agent. This agent was synthesized via ring‐opening polymerization of lignin and lactide. The effects of LG‐g‐PLA on cell nucleation induced by the crystallization, rheological behavior, and foamability of PLA were evaluated. Results indicated that LG‐g‐PLA can improve the crystallization rate and crystallinity of PLA, and play a significant nucleation role in the microcellular foam processing of PLA. LG‐g‐PLA improved the foam morphology of PLA, obtaining a reduced and uniform cell size as well as increased expansion ratio and cell density. With the addition of 3 wt% LG‐g‐PLA content, the PLA/LG‐g‐PLA foams increased the compressive strength 1.6 times than that of neat PLA foams. The improved foaming properties of PLA via a biobased nucleating agent show potential for the production and application of green biodegradable foams.

Relationship among Extrusion Conditions, Cell Morphology, and Properties of Starch‐Based Foams—A Review

“…Under this condition, the mechanical energy (SME) is reduced because the higher starch granule disruption and the viscosity diminishes. However, above 18 wt% water content, ER decreases following an inversely proportional relationship with foam density [ 64 ] because a greater water vapor content is released from the starch matrix. This effect was also reported by Shi et al.…”

Effect of nano TiO2 on the cellular structure and mechanical properties of wood flour/polypropylene composite foams via mold‐opening foam injection molding

“…1,2 The introduction of a microcellular structure can greatly reduce the polymer density and improve its ductility and impact resistance, thus achieving the effects of both lightweight and high strength WPC products. [3][4][5][6][7] And these products can potentially be developed as energy absorbing materials, which are extensively used in automotive, building, packaging and other industries. [8][9][10] Recently, foaming technology using supercritical fluid (typically CO 2 and N 2 ), an ideal and environmental-friendly method, has received broad consideration for the fabrication of microcellular WPCs via extrusion and injecting molding.…”

“…However, applications for traditional WPC production have been limited, due to their high density and brittleness and poor impact resistance 1,2 . The introduction of a microcellular structure can greatly reduce the polymer density and improve its ductility and impact resistance, thus achieving the effects of both lightweight and high strength WPC products 3–7 . And these products can potentially be developed as energy absorbing materials, which are extensively used in automotive, building, packaging and other industries 8–10 .…”

Poly(Lactide)-Modified Lignin Nanofibers: Investigating the Role of Polymer Tacticity on Fiber Properties and Filtration Efficiency

“…We were interested in the study by Sattely and co-workers who used graft copolymerization of lignin and PLA to overcome the challenge of their different solubilities in pristine forms . Since this pioneering study, others have also developed methodologies for the synthesis of lignin- graft -PLA copolymers through ring-opening polymerization of rac -lactide ( rac -LA), l -lactide (L-LA), and d -lactide (D-LA), yielding corresponding PDLLA, PLLA, and PDLA grafts. ,,,− Many studies used them as compatibilizers to toughen PLA by improving the dispersion of lignin. − ,− These lignin- graft -PLA/PLA composite materials were suitable for ultraviolet (UV) blocking, active food packaging, and biomedical applications. ,,,,,, …”