Effects of in-situ crystallization on poly (lactic acid) microcellular foaming: Density functional theory and experiment. (18th June 2020)

• Record Type: Journal Article
• Authors: Yu, Kesong; Ni, Jingyue; Zhou, Hongfu; Wang, Xiangdong; Mi, Jianguo
• Is Part Of: Polymer. Volume 200(2020)
• Publication Date: 2020-06-18
• Subjects: Poly(lactic acid) -- In-situ crystallization -- DFT bubble Nucleation; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2020.122539
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: In this work, poly(lactic acid) (PLA) crystallization was induced during the saturating process as a nucleation agent to prepare CO2 blown PLA foam. To explore the foaming mechanism, the density functional theory (DFT) approach was applied. The unit cell structure of PLA crystal was carefully considered. Calculated density profile and energy barrier showed that the induced crystals had a large effect on improving CO2 local density and decreasing the nucleation energy barrier. Then, cellular density was obtained through quantitive calculation, and the influence of crystallinity on bubble nucleation was measured qualitatively. To verified theoretical calculation, corresponding foaming experiments were also adopted. The comparison of calculation and experiments showed the bubble nucleation efficiency was significantly enhanced, around 5 orders of magnitude, when assisting with in-situ PLA crystals. The consistent theoretical and experimental data demonstrated that DFT can be applied to make deeper comprehension of the nucleation mechanism of the microcellular foaming of PLA. Graphical abstract: Image 1 Highlights: Unit cell structure and crystallinity/crystalline lamella of PLA crystals are considered within the DFT approach. Nucleation energy barriers crystals are calculated quantitatively and cellular density is predicted qualitatively. Influence of PLA crystals on bubble nucleation is tested by experimental data.