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采用傅里叶变换红外光谱、核磁共振波谱和紫外-可见吸收光谱3种表征方法 ,对热塑性聚氨酯弹性体(TPU)在紫外光老化、微波老化和热氧老化条件下的老化行为进行了研究,探讨了TPU的老化机理.研究结果表明:在微波老化和热氧老化中,TPU有着相同的老化机理,初期因热导致TPU样品的后熟化,使样品中残余的异氰酸酯与水解得到的伯胺反应生成脲基,并进一步反应生成缩二脲基团.延长微波老化时间至30min后,大部分的TPU硬段分解,主产物为TPU链段组成之一的聚己二酸丁二醇酯(PBA).微波老化可明显加快热氧老化进程,TPU在微波下老化15min等效于热氧老化600h.TPU在紫外光下老化,其化学结构无明显变化,随老化时间的延长,氢键化的氨酯基增多,氢键含量增大,仅少量氨酯键断裂,生成烯胺,导致外观变黄.
The aging behavior of thermoplastic polyurethane elastomer (TPU) under ultraviolet light aging, microwave aging and thermo-oxidative aging was studied by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy and UV-Vis absorption spectroscopy. The mechanism of TPU aging was discussed.The results show that TPU has the same aging mechanism in microwave and thermo-oxidative aging. The initial aging of TPU caused by the heat causes the residual isocyanates in the sample to react with the hydrolyzed primary amines Urea group was formed and further reacted to form biuret group.After prolonging the aging time of microwave to 30min, most of TPU hard segment was decomposed and the main product was polybutylene adipate (PBA ) .The microwave aging can obviously accelerate the process of thermo-oxidative aging, the aging of TPU under microwave for 15min is equivalent to thermo-oxidative aging 600h.TPU ages under UV light, its chemical structure has no obvious change, with the aging time prolonging, hydrogen bonding Increased urethane group, hydrogen bond content increased, only a small amount of urethane bond cleavage, enamines, resulting in the appearance of yellow.