Crystalline transition and morphology variation of polyamide 6/CaCl2 composite during the decomplexation process

In this work, we developed a new method to prepare porous PA6 with different morphologic feature and crystalline forms via the decomplexation of PA6/CaCl2 composite. The structures and morphology of thus obtained materials were characterized by vibrational spectroscopy (FT-IR and Raman) and scanning electron microscope (SEM) method. When amorphous PA6/CaCl2 composite films were treated in water at room temperature, PA6 re-arranges into γ form. However, decomplexation of the PA6/CaCl2 composite in boiling water produces PA6 in α crystalline form. If the PA6/CaCl2 composite is soaked in methanol, part of PA6 is dissolved or swollen in methanol/metal salt solutions. As a result, a dissolve/precipitation process occurred during the decomplexation process, which led to the formation of PA6 in α crystalline form. Further investigation demonstrates that the morphologies of the porous PA6 could be adjusted by using different solvents and/or different decomplexation conditions.