Polylactic Acid Chemical Foaming Assisted by Solid-State Processing: Solid-State Shear Pulverization and Cryogenic Milling

Semi-conductive foams based on low-density polyethylene/ethylene-vinyl acetate copolymer (LDPE/EVA) blends in the presence of carbon nanotubes (CNTs) were prepared using a twin-screw extrusion process. The effects of CNTs content and localization state in the binary mixture on the physical and structural properties of LDPE/EVA/CNT foams were investigated. The results confirmed that the void fraction, cell density, bubble size and cell size distribution of foams are optimal against CNT loading. The lightest LDPE/EVA/CNT foam was obtained by the CNT localization in the LDPE matrix. This foam containing 2.5 phr of CNT had smaller cells and more uniform cell size comparing to the pure blend foam. The cell density of this foam was 1.598 × 106 cells/cm3, which is much larger than that for the blend foam, 8.64 × 105 cells/cm3. However, the CNT localization state in the dispersed EVA domains resulted in lower void fractions and cell densities comparing with the LDPE/EVA blend foam. The findings clarify the profound impact of the nanofiller localization state on the foam properties of the binary polymeric systems. Light semiconductive LDPE/EVA foams with small cells, uniform cell size and high cell densities were achieved by localizing and dispersing the CNT nanoparticles in the LDPE matrix phase.

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“…The void fraction (Vf) of sample foams was calculated based on ASTM D2734 using the following equation: 31,32 …”

Section: Methodsmentioning

confidence: 99%

Extrusion foaming of multiphasic polyethylene/ethylene-vinyl acetate copolymer/carbon nanotube mixtures: Tailoring foam properties by selective localization of nanoparticles

Ghanemi

Mousavi

Qewami

et al. 2023

Journal of Cellular Plastics

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“…Onffroy et al [19] presented an effective chemical foaming process of polylactic acid (PLA) via the solid-state processing methods of solid-state shear pulverisation (SSSP) and cryogenic milling. The effects of the pre-foaming solid-state processing method and chemical foaming agent (CFA) concentration were investigated.…”

mentioning

confidence: 99%

Advances in Sustainable Polymeric Materials

Cazan

2022

Polymers

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Cryogenic Impact-Induced Pulverization Process for Fast, Highly Crystallized, and Nucleating Agent-free PLA with High Heat Resistance

Lee,

Ko,

et al. 2024

ACS Appl. Polym. Mater.

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Biodegradable polymers such as poly(lactic acid) (PLA) are expanding into wider fields as substitutes for nonbiodegradable plastics. However, a viable option to improve the crystallization and heat resistance properties of PLA in the industry is the use of nonbiodegradable nucleating agents. Thus, this study presents a preprocessing method for enhancing PLA properties while maintaining biodegradability without using nucleating agents. The PLA preprocessed with cryogenic impactinduced pulverization (CIIP) demonstrates a self-nucleation (SN) behavior. This SN effect was systematically investigated by examining the crystallization during the molding process under various CIIP conditions. As a result, the crystallinity of CIIPtreated PLA increased by 36.2% through densely organized nucleation sites, and the crystallization rate was 80.1% faster at 8.5 min compared to pellet-type PLA (42.8 min). Additionally, the SN effect induced through the CIIP process preserved the stable crystal structure, improving crystallization even with repeated melting. The improved melt-recrystallization behavior by SN agents was evident in injection molding. Consequently, the heat distortion temperature (HDT) increased, improving heat resistance by up to 81.3%. These effects are expected to be practical for improving productivity and quality during the injection molding process. Therefore, this study can expand the scope of biodegradable and sustainable materials by applying PLA with the SN effect realized through the CIIP process to various fields.

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Polylactic Acid Chemical Foaming Assisted by Solid-State Processing: Solid-State Shear Pulverization and Cryogenic Milling

Cited by 3 publications

References 67 publications

Extrusion foaming of multiphasic polyethylene/ethylene-vinyl acetate copolymer/carbon nanotube mixtures: Tailoring foam properties by selective localization of nanoparticles

Extrusion foaming of multiphasic polyethylene/ethylene-vinyl acetate copolymer/carbon nanotube mixtures: Tailoring foam properties by selective localization of nanoparticles

Advances in Sustainable Polymeric Materials

Cryogenic Impact-Induced Pulverization Process for Fast, Highly Crystallized, and Nucleating Agent-free PLA with High Heat Resistance

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