Synthesis of polyether imidazole ionic liquid and its modification on polypropylene crystal structure and mechanical properties

Abstract

Polyether imidazole ionic liquid (PIIL) was synthesized from N-ethyl iminazole and hydroxyl-terminated polyepichlorhydrin, produced through cationic ring-opening polymerization of epichlorohydrin using Et2O·BF3 as catalyst, and utilized for the modification of polypropylene (PP) by the method of melt blending. The prepared PIIL was characterized by Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy. The resulting composite of PP and PIIL was characterized by differential scanning calorimetry and X-ray diffraction analyses. With PIIL acting as a nucleating agent, the crystal structure of PP transformed from α to β crystalline form after modification, while crystallization peak temperature was kept unchanged. Comparison test of the mechanical properties of pure PP and PP/PIIL proved that the long flexible chain of PIIL achieved good compatibility with PP and had reinforcing and toughening effects on PP. With the increase of ionic liquid in PP, both the impact strength and the breaking elongation of the PP/PIIL composite were significantly improved.