Smorawska Joanna, Włoch Marcin, Głowińska Ewa
Department of Polymers Technology, Faculty of Chemistry, Gdansk University of Technology, 11/12 Gabriel Narutowicza Street, 80-233 Gdansk, Poland.
Materials (Basel). 2023 Sep 17;16(18):6246. doi: 10.3390/ma16186246.
Currently, the growing demand for polymeric materials has led to an increased need to develop effective recycling methods. This study focuses on the multiple processing of bio-based thermoplastic polyurethane elastomers (bio-TPUs) as a sustainable approach for polymeric waste management through mechanical recycling. The main objective is to investigate the influence of two reprocessing cycles on selected properties of bio-TPUs. Two series of bio-based TPUs were synthesized via a solvent-free two-step method with the use of hexamethylene diisocyanate or hexamethylene diisocyanate/partially bio-based diisocyanate mixtures, bio-based poly(triamethylene ether) glycol, and bio-based 1,3 propanediol. Both the raw bio-TPUs and those subjected to two reprocessing cycles were examined with respect to their chemical, physical, thermal, thermomechanical, and mechanical properties. The conducted research revealed that reprocessing led to changes in the phase separation between the hard and soft segments, thereby affecting the bio-TPUs' properties. Both series of materials showed similar chemical structures regardless of reprocessing (slight changes were observed in the range of carbonyl peak). The thermal properties of TPUs exhibited slight differences after each reprocessing cycle, but generally, the non-processed and reprocessed bio-TPUs were thermally stable up to about 300 °C. However, significant differences were observed in their mechanical properties. The tensile strength increased to 34% for the twice-reprocessed bio-TPUs, while the elongation at break increased by ca. 200%. On the other hand, the processing cycles resulted in a decrease in the hardness of both bio-TPU series (ca. 3-4 °ShA). As a result, the prepared bio-TPUs exhibited characteristics that were closer to those of the sustainable materials model, promoting the circular economy of plastics, with environmental benefits arising from their recyclability and their high content of bio-based monomers (78.4-78.8 wt.%).
目前，对聚合物材料不断增长的需求导致开发有效回收方法的需求增加。本研究聚焦于生物基热塑性聚氨酯弹性体（生物基TPU）的多次加工，作为通过机械回收进行聚合物废物管理的可持续方法。主要目的是研究两个再加工循环对生物基TPU选定性能的影响。通过无溶剂两步法，使用六亚甲基二异氰酸酯或六亚甲基二异氰酸酯/部分生物基二异氰酸酯混合物、生物基聚（三亚甲基醚）二醇和生物基1,3 - 丙二醇合成了两个系列的生物基TPU。对原始生物基TPU和经过两个再加工循环的TPU的化学、物理、热、热机械和机械性能进行了检测。进行的研究表明，再加工导致硬段和软段之间的相分离发生变化，从而影响生物基TPU的性能。无论是否再加工，两个系列的材料都显示出相似的化学结构（在羰基峰范围内观察到轻微变化）。每次再加工循环后，TPU的热性能表现出轻微差异，但一般来说，未加工和再加工的生物基TPU在高达约300℃时热稳定。然而，它们的机械性能存在显著差异。两次再加工的生物基TPU的拉伸强度提高到34%，而断裂伸长率增加了约200%。另一方面，加工循环导致两个生物基TPU系列的硬度降低（约3 - 4°ShA）。结果，制备的生物基TPU表现出更接近可持续材料模型的特性，促进了塑料的循环经济，因其可回收性和高含量的生物基单体（78.4 - 78.8 wt.%）而具有环境效益。
