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Ionic liquids (ILs) are liquid salts at ambient or lower temperatures and consist of ions and short-lived ion pairs. They are potential alternatives to toxic, hazardous, highly flammable, and volatile solvents for preparing solutions, dispersions, gels, composites, and polymeric melts. ILs have some very interesting and unique characteristics like good chemical and thermal stability and very low vapor pressures. They have good solvation interactions with a wide range of organic, inorganic, and polymeric compounds. They can enhance colloidal stability and the elasticity range of polymers. ILs are environmental friendly, easily recyclable, and structurally similar to the conventional solvents. For optimal performance, it is necessary to fully understand the rheological properties of ILs and their different systems for academic interests such as understanding the ability of ILs as processing aids particularly in film casting, fiber spinning and spraying, comprehension of thermodynamics and dynamics of polymer chains in ILs, analyzing the hydrodynamic volume of dispersed polymer, polymer–ILs interactions, characterizing the viscoelastic properties and nanophase–ILs interactions in nanocomposite systems, analyzing the plasticization efficiency, and the final properties of the composite system. The rheological analysis is also important for industrial purposes particularly for designing processing techniques and suitable operating conditions for IL based systems. The aim of this review is to give an overview of the rheological properties of pure ionic liquids and solutions, dispersions, gels, composites, and melts based on ionic liquids.

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Abstract-Used cooking oils are of increasing interest as inexpensive feedstock for biodiesel production. In this work, we characterized the used cooking oil collected from the cafeteria in Universiti Teknologi PETRONAS. The spectroscopic analysis was performed for the used and unused cooking oil samples. Comparison of the data indicated that no significance spectroscopic and structural changes occurred for used and unused oil samples. The results indicate high degree of saturation and mono unsaturated fatty acids in the oil. The viscosity and acid value of the used oil was considerably higher than the unused oil. It can be concluded on the basis of our results that the difference in the behaviour and performance of oil is not only due to the main components (triglycerides) but also due to minor components (Vitamin E).Index Terms-FTIR, 1 HNMR, TGA, triglycerides, unused and used palm oil.