Polyester Fiber Fabric Reinforced Polyurethane Composites Preparation And Properties

Polymeric composites have been widely focused by researchers due to its excellent properties, such as mechanical, tribological, electrical, thermal and optical properties. So the fabric composites based on the complex structure of the fabrics, not only have excellent ductility and lubricant property of polymers, but also have high specific strength, wear resistance and thermal resistance of fabrics. The attractiveness of polyurethane (PU) to be the matrix of composites stems from its excellent processability, standout bonding to different substrates, absence of volatile organic compounds (VOC), and favorable economics. Whereas, the tribological property of PU is not good enough. In this thesis, the polyurethane matrix has been modified and reinforced by the polyester fabrics in order to improve its thermal, mechanical and tribological performance. Firstly, the components of the PU adhesives and their influence on the performance of the whole composites were studied; secondly, the micro-scale solid lubricant and nano-scale fillers were chosen to modify the polyester (PET) reinforced polyurethane (PU) composites, and studied on the aspects of mechanical and tribological properties. Furthermore, SEM, OM and FT-IR were used to detect the micro-morphology and the chemical structure of the modified composites. The results showed that:1) As the content of the component-NCO-in the PU matrix increased, the thermal stability became worse, but the tensile property, hardness and the tribological resistance were all improved.2) When the MoS2 fillers were used to modify the composites, the thermal stability decreased with the increase of the MoS2 fillers. But due to the polar bonds on the surface of the molecule and the flexible lamella structure, both of the tensile and the tribological performance were improved.3) When the nano-Al2O3 fillers were used to modify the composites, the tensile performance was a little improved but not as excellent as that of MoS2. Under the condition of dry sliding, the agglomerated nano fillers acted as the abrasive particles which aggravated the wear; when the lubricant oil was added to the worn surface, the nano-Al2O3 modified composites presented the excellent tribological performance, because the nano particles with the high surface energy combined with the lubricant oil, together acting as the transfer film which protected the wear surface of the composites.4) On the basis of the results above, fabrication of an optimal PU based polyester fabric composite was proposed to take into account the ratios of the bi-component PU adhesives and the structures of fillers. To sum up, PU based PET composites with relatively low content of crosslink groups tends to have better thermo-stability. The PET fabric reinforced PU composites modified by MoS2 have good tensile property and tribological performance under dry sliding, but relatively bad thermal performance. And under the oil lubrication, nano-Al2O3 fillers can make the composites reach the relatively higher tribological performance.5) Furthermore, the loading direction and the friction direction of the composites also have been studied in this thesis. When the loads and frictions are on the on-axis directions, PET fabric reinforced PU composites have better tensile and tribological performance than those when the loads and frictions are on the off-axis directions. Furthermore, the best tensile and tribological resistance of the composites has been attained along the warp direction.