Compositional elements of thermoplastic polyurethanes for reducing the generation of acetaldehyde during thermo-oxidative degradation

Volatile organic compounds (VOCs) have been become of prime importance in polymer industry due to the increased concerns regarding their effects on the environment and health. Comprehensive understanding of the factor controlling the generation of VOCs and the development of a quantitative analytical tool for tracking the generation of VOCs have thus been an important topic for researchers. In this study, thermoplastic polyurethanes (TPUs) composed of different polyols, diisocyanates, and chain extenders were carefully synthesized to investigate the effect of the compositional factors on the generation of VOCs, especially acetaldehyde (AA). Headspace-gas chromatography equipped with simple flame-ionization detector (HS-GC-FID) was successfully set-up for the quantitative monitoring of the generation of AA at different thermal treatment temperatures and times. The generation of AA was accompanied by the degradation of TPU chains during the thermal treatments, as evidenced by the decreased molecular weight of the TPUs. Interestingly, TPUs with polyester- and polycarbonate-based TPUs exhibited a significant reduction of AA emissions, compared with TPUs with typical polyether-based polyols, poly(propylene glycol). TPUs with aromatic diisocyanates and chain extenders also emitted much less AA during the thermal treatments than TPUs with aliphatic diisocyanates and chain extenders. These results indicated the importance of the compositional factors of the TPUs for the generation of AA. Understanding and optimization of the compositional factors of the TPU by using HS-GC-FID can be a useful tool for reducing the generation of AA.