Mechanical and Thermal Properties of Biocomposites Based on Polyethylene from Renewable Resources Modified with Ionic Liquids

Biocomposites based on polyethylene from renewable resources derived from sugar cane as raw material were modified with phosphonium ionic liquids. Mechanical properties and thermal behavior of modified biocomposites in air atmosphere were studied. The influence of ionic liquids (IL) on thermal degradation of biocomposites based on polyethylene from renewable resources was studied by thermogravimetric analysis (TGA). Three phosphonium ionic liquids containing phosphorus both in cation and anion segments were used. Biocomposites were filled with 10 wt% and 20 wt% hemp fiber. In general, modification of biocomposites reinforced with 20 wt% hemp fiber with phosphonium ionic liquids resulted in improvement of tensile properties, i.e. tensile strength, as well as impact strength and hardness, whereas Young’s modulus decreased compared to unmodified biocomposites. Thermal degradation of biocomposites modified with phosphonium ILs containing phosphate anion proceeds in two steps corresponding to overlapping processes of degradation of polymer matrix and decomposition of hemp fibers components. Conversely, biocomposites modified with ionic liquid based on phosphinate anion exhibit more complex degradation behaviour, as well as slightly enhanced thermal stability. It may indicate that anion segment of ionic liquids influences the thermal behavior of ILs modified biocomposites.