Effect of bio-based components on the chemical structure, thermal stability and mechanical properties of green thermoplastic polyurethane elastomers

Abstract

It seems to be obvious that conditions changes during polyols synthesis have impact on the polyols properties. Even the chemical formula is the same or similar, physicochemical properties and also molecular weight of polyols might be different and are significant in term of future polyurethanes properties and processing. In this work, fully bio-based poly(propylene succinate)s synthesized at different temperature conditions were used as a polyol in thermoplastic polyurethane elastomers (TPU) synthesis. Novel bio-based TPUs were synthesized with the use of mentioned bio-based linear polyester polyols, poly(propylene succinate)s and also 4,4-diphenylmethane diisocyanate (MDI) and a chain extender 1,4-butanediol (BDO) or 1,3-propanediol (PDO), both with the natural origin. Influence of synthesized bio-based polyols on thermoplastic polyurethane elastomers characteristic was determined based on investigation of chemical structure, thermal, thermomechanical, mechanical and physical properties of synthesized bio-based TPU. Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H NMR) were applied to the chemical formula determination. Thermogravimetry was supportive in thermal analysis, dynamic mechanical analysis (DMA), tensile test and hardness were used to determine thermomechanical behavior and mechanical properties at static and dynamic condition. The density of the obtained materials was also measured. It was established that using obtained fully bio-based polyester polyols the thermoplastic polyurethane elastomers can be synthesis without catalyst usage. Based on the results demonstrated greater influence of type of chain extender on bio-based TPU properties than condition of bio-based polyester synthesis. Each sample was characterized by glass temperature (Tg) ca. 0–5 °C and similar thermal stability ca. 320 °C. The tensile strength of prepared bio-based TPUs reach even 30 MPa with an elongation at break ca. 550%.