A method for regulating crystallization was developed to prepare micro- and nano- cellular foams of polybutylene terephthalate (PBT) using supercritical CO₂ (scCO₂). This method involves the formation of branching and crosslinking structures in PBT. After modification, the crystallization temperature of PBT increased from 191.7 to 195.8 °C, while its enthalpy of crystallization decreased from 46.8 to 41.3 J/g and disordered lamellar crystals were formed, particularly, in the case of PBT with a crosslinking structure. In addition to enhanced viscosity and heterogeneous nucleation owing to lamellar crystals, a transition from microcellular foam to nanocellular foam was achieved after the modification of PBT. Interestingly, the transition was only observed in PBT with a crosslinked structure because of its significantly reduced crystallinity, which prevented the appearance of large unfoamed areas. As a result, microcellular PBT foams transformed to nanocellular PBT foams with a cell size of 0.33 µm and cell density of 6.37 × 10¹³ cells/cm³ upon optimizing the polymer chain structure and supercritical CO₂ foaming conditions such as the saturation temperature and saturation time.

开发了一种调节结晶的方法，以使用超临界 CO ₂ (scCO ₂）。该方法涉及在 PBT 中形成支化和交联结构。改性后，PBT的结晶温度从191.7升高到195.8°C，而其结晶焓从46.8降低到41.3 J/g，形成了无序的层状晶体，特别是在具有交联结构的PBT的情况下。除了由于层状晶体提高粘度和异相成核外，PBT 改性后还实现了从微孔泡沫到纳米孔泡沫的转变。有趣的是，这种转变仅在具有交联结构的 PBT 中观察到，因为它的结晶度显着降低，这阻止了大面积未发泡区域的出现。结果，微孔 PBT 泡沫转变为孔尺寸为 0 的纳米孔 PBT 泡沫。在优化聚合物链结构和超临界CO ₂发泡条件（如饱和温度和饱和时间）后，^{13 个孔}/cm ³。