Effect of the interchain interaction on the crystallization kinetics and crystal structure of polylactic acid under nitrogen

In order to prepare polylactic acid (PLA) foam material with excellent performance by utilizing nitrogen (N₂), the crystallization behavior of PLA under N₂ needs to be urgently studied. This article in situ investigated for the first time the impact of N₂ on the crystallization kinetics of PLA. Meanwhile, the influence of N₂ on the crystal structure and crystallization process of PLA was studied. Research has shown that at different crystallization temperatures and N₂ pressures, N₂ exhibited different effects on the crystallization kinetics and crystal structure of PLA. At low crystallization temperature and N₂ pressure, N₂ promoted the growth of PLA spherulites. As the crystallization temperature increases, the maximum N₂ pressure that could accelerate the spherulite growth rate of PLA was also higher. Furthermore, under experimental pressure, N₂ would cause more α′ crystals to form in PLA at low crystallization temperatures. At high crystallization temperatures, the N₂ pressure showed much less impact on the crystalline structure of PLA than that of temperature. In addition, N₂ inhibited the cold crystallization of PLA, reducing the crystallization temperature range and cold crystallization enthalpy.