PDF(Pubmed)
Abstract：
The benefit of being acquainted with thermal properties, especially the thermal stability of polyurethanes (PU), and simplified methods for their improvement is manifold. Considering this, the effect of embedding different amounts of unmodified and surface-modified TiO2 nanoparticles (NPs) within PU, based on polycaprolactone (PCL) and Boltorn® aliphatic hyperbranched polyester, on PU properties was investigated. Results obtained via scanning electron microscopy, swelling measurements, mechanical tests and thermogravimetric analysis revealed that TiO2 NPs can be primarily applied to improve the thermal performance of PU. Through surface modification of TiO2 NPs with an amphiphilic gallic acid ester containing a C12 long alkyl chain (lauryl gallate), the impact on thermal stability of PU was greater due to the better dispersion of modified TiO2 NPs in the PU matrix compared to the unmodified ones. Also, the distinct shape of DTG peaks of the composite prepared using modified TiO2 NPs indicates that applied nano-filler is mostly embedded in soft segments of PU, leading to the delay in thermal degradation of PCL, simultaneously improving the overall thermal stability of PU. In order to further explore the thermal degradation process of the prepared composites and prove the dominant role of incorporated TiO2 NPs in the course of thermal stability of PU, various iso-conversional model-free methods were applied. The evaluated apparent activation energy of the thermal degradation reaction at different conversions clearly confirmed the positive impact of TiO2 NPs on the thermal stability and aging resistance of PU.
摘要：
熟悉热特性的好处，特别是聚氨酯(PU)的热稳定性，简化的改进方法是多方面的。考虑到这一点,在PU中嵌入不同量的未改性和表面改性的TiO2纳米颗粒（NPs）的效果，基于聚己内酯（PCL）和Boltorn®脂肪族超支化聚酯，对PU性能进行了研究。通过扫描电子显微镜获得的结果，膨胀测量，力学测试和热重分析表明，TiO2NPs可以主要用于改善PU的热性能。通过用含有C12长烷基链的两亲性没食子酸酯（没食子酸月桂酯）对TiO2NP进行表面改性，与未改性的PU相比，改性TiO2NP在PU基质中的分散性更好，对PU热稳定性的影响更大。此外，使用改性TiO2NP制备的复合材料的DTG峰的明显形状表明，所应用的纳米填料主要嵌入PU的软段中，导致PCL的热降解延迟，同时提高PU的整体热稳定性。为了进一步探索制备的复合材料的热降解过程，证明掺入TiO2NPs在聚氨酯热稳定性过程中的主导作用，应用了各种等转换无模型方法。在不同转化率下评估的热降解反应的表观活化能清楚地证实了TiO2NP对PU的热稳定性和耐老化性的积极影响。
