Effect of long‐chain branching structures on supercritical CO₂ foaming behavior of iPB‐1 with different crystalline form ratios

AbstractTo solve the poor cellular morphology of linear iPB‐1 during supercritical CO2 foaming, the modification and the special crystalline transition behavior of iPB‐1 were used to improve its foaming performance. Based on free radical polymerization, long‐chain branching iPB‐1 is achieved. Long‐chain branching structures not only reduce crystallinity of iPB‐1, but also increase the crystallization temperature. Long‐chain branching structures can accelerate the crystalline transformation rate of iPB‐1. After annealing at room temperature for 24 h, the crystalline transformation of the raw iPB‐1 material is completed by 14%, while long‐chain branching iPB‐1 reaches 33%. The crystalline transformation of the modified iPB‐1 is completed by 85% after annealing for 48 h. Compared with the raw iPB‐1 material with crystalline form I, the introduction of long‐chain branching structures is favorable for broadening the foaming temperature interval from 10 to 20°C, while the foaming temperature interval of the long‐chain branching iPB‐1 with crystalline form II increases to 25°C. The iPB‐1 with high content of crystalline form I and long‐chain branching structures are conductive to the formation of uniform cells. This will broaden the application of iPB‐1 foam in automotive interiors, packaging, and transportation fields.