To Effectively Tune the Cell Structure of Poly(ethylene 2,5-furandicarboxylate-co-ethylene terephthalate) Copolyester Foams via Conducting a Prior Isothermal Melt Crystallization

The objective was to effectively tune the cell structure of poly(ethylene 2,5-furandicarboxylate-co-ethylene terephthalate) (PEFT) copolyester foams via creatively conducting isothermal melt crystallization prior to batch foaming. First, the chemical structure of PEFT was characterized. Second, isothermal melt crystallization at 220 degrees C was conducted to explore its effect on the foaming behavior of poly(ethylene terephthalate) (PET), PEFT5%, and PEFT10%. Third, isothermal melt crystallization at various temperatures was conducted to reveal its effect on the cell structure. Fourth, the cell structure variation with the crystallinity was studied. Fifth, the effect of isothermal crystallization on thermal insulation of PEFT foams was studied. It was found that different proper temperatures are required for PET, PEFT5%, and PEFT10% to conduct isothermal melt crystallization. The cell structure parameters including the cell size, cell density, and expansion ratio show similar variation trends with the isothermal crystallization temperature or with the crystallinity for all three samples, and the general rule of the cell structure variation with the crystallinity is proposed. Based on this, cell structure-tunable PEFT foams are fabricated, showing good thermal insulation performance. This study is of great importance for effectively tuning the cell structure and expanding the applications of PEFT foams.