Effect of carbon dioxide on lamellar arrangement in poly(lactic acid) ring band spherulites

Abstract

In this research, the formation of ring band spherulite of poly(lactic acid) (PLA) under carbon dioxide (CO2) was in‐situ studied and the internal lamellar arrangement of ring band spherulite formed under CO2 was revealed for the first time. The spherulites by PLA crystallized under air and different CO2 pressures have been studied, and the surface and internal lamellar arrangement of the ring band spherulites have also been analyzed in detail. It was found that PLA would form ring band spherulite under air and 6 MPa CO2, while the internal structures of the two types of ring band spherulites were different. The surface height difference of ring band spherulites formed under air was small, at 278.9 nm, and the twisting angle of the lamellae was also small. However, the difference in the surface height of the ring band spherulite formed under 6 MPa CO2 was big, reaching 778.3 nm. Through analysis on the internal lamellar arrangement of the ring band spherulite, it was found that the valley for the ring band spherulites formed under 6 MPa CO2 was composed of flat‐on lamellae, the ridge was composed of edge‐on lamellae and the sudden twist occurred between the flat‐on lamellae and edge‐on lamellae.

Preparation of Controllable and Repeatable Crystalline States through Step-by-Step Self-Nucleation Programming and Its Application for Improving the PTC Reproducibility of trans-1,4-Polyisoprene/Carbon Black Composites

“…Figure a shows the crystallization state of TPI obtained after quenching from the molten state to 40 °C and annealing for 30 min, which then begins to cool down and is sequentially recorded in Figure b,c. POM can be used to observe and obtain information about crystals, including nucleation and growth processes. − Taking the crystals in the yellow box as an example, many new crystals nucleate rapidly around their surfaces and are used to characterize the role of the original crystal as a “nucleating agent” in the subsequent nonisothermal crystallization process, thereby expressing the effect of SN on the increase of nucleation density in the system. The POM image of the crystalline state after annealing for 5 min at T s = 60 °C is displayed in Figure d.…”