Plasticization of flame-retardant and non-flame-retardant compounds based on Thermoplastic Polyurethane

The objective of this work is to investigate the plasticization of polyether-based thermoplastic polyurethane (TPU) using plasticizers with varying chemical characteristics, specifically benzoate-type and phosphate-type plasticizers. The formulations of plasticized TPU were assessed from both thermal and mechanical perspectives to determine the effects of plasticization on these properties. Comparisons were made between benzoate-based and phosphate-based plasticizers to highlight how their distinct chemical structures influence the material’s behaviour. Additionally, a bio-based plasticizer was studied to identify a more sustainable alternative compatible with the TPU-polyether matrix. The mechanical and thermal properties of the bio-based plasticizer were evaluated and compared with existing results. A key focus of this thesis was the examination of the flame-retardant properties of polyether-based TPU compounds using an industrially utilized flame retardant. Both benzoate-based and phosphate-based plasticizers were analysed to understand how their structural differences affect fire resistance, with particular attention given to the potential advantages of phosphate-based plasticizers in enhancing flame retardancy. Benzoflex 2088, the industry standard plasticizer for TPU matrices, served as a reference for comparison with the other plasticizers. The findings indicate that the choice of plasticizer significantly influences the mechanical and thermal properties of TPU-polyether. The low molecular weight benzoate-based plasticizer emerged as a strong substitute for Benzoflex 2088, offering nearly identical properties while providing the advantage of being a solid plasticizer. In contrast, the high molecular weight benzoate-based plasticizer consistently delivered inferior results compared to the reference. The phosphate-based plasticizers exhibited lower performance relative to Benzoflex 2088; however, the liquid phosphate-based plasticizer demonstrated significant advantages in flame-retardant compounds. In flame-retardant systems, this liquid phosphate-based plasticizer exhibited strong synergy with the industrially used flame retardant chosen for this work, resulting in enhanced fire resistance and achieving a V-0 classification in the UL-94 standard test. This was accomplished without compromising the mechanical and rheological properties of the TPU. The study also explored eco-friendly alternatives, particularly a 100% bio-based plasticizer, which showed promising results at concentrations below 30%. However, its performance diminished due to saturation effects beyond this concentration. Overall, the research underscores the importance of selecting and optimizing plasticizers to tailor TPU properties for specific industrial applications, such as the manufacturing of electrical cables for automobiles.