Synthesis And Properties Of The Casting Nano-Silica/ Polyurethane Composite

The purpose of the paper is enforcing the PUR elastomer through nano-SiO₂ modification, and improving the mechanical properties, heat-resisting properties and dumping proprieties.In this paper the effects of composes and synthesis parameters on polyurethane properties have been studied, nano-SiO₂/PUR composites through in-situ polymerization have been synthesized, and the effects of different synthesis process,composes and synthesis parameters on the performances of Nano-composites have been studied.The results of the study indicate:(1)The properties of PUR can increased obviously by optimizing composes and synthesis parameters. After all-around consideration, when the TDI/ PBAG ratio at 3.5,NH2/NCO ratio at 0.95,sulfuration temperature at 100℃and sulfuration time at 16h,the PUR have the best tensile proprieties.(2)The nano-SiO₂/PUR composites have been synthesized by in-situ polymerization and prepolymer polymerization. The SEM photos show the nano-SiO₂ dispersed in the composites synthesized by in-situ polymerization homogeneously,the size of most nano-SiO₂ is under 50nm.(3)FTIR spectrums show: the absorbing peak value of–NHCO– decreased because of the chemical reaction between nano-SiO₂ and TDI; the absorbing peak value of Si-O-C comes out because of the chemical reaction between nano-SiO₂ and PUR elastomer.(4)The nano-SiO₂/PUR composites synthesized by in-situ polymerization have improved tensile properties and hardness compare to the pure PUR; as the content of nano-SiO₂ increase, the tensile strength has increased greatly, the elongation at break and the hardness have also improved, the nano-composites have the best mechanical property When the nano-SiO₂ content at 2.0wt%.KH-550 have a positive effect on the mechanical property of nano-composites, nano-composites have the best mechanical property When the KH-550 content at 2.0wt%-2.5wt%.(5)The Tg increases when the the content of nano-SiO₂ have increased. When the content of nano-SiO₂ at 2.0wt%, the Tg increased 16.2K compare to the pure PUR. So the heat-resisting properties of nano-composites have improved; and the effective temperature span have enlarged.(6)The nano-SiO₂/PUR composites have higher reserve energy modulus and tanδthan the pure PUR elastomer, the reserve energy modulus and tanδincrease as the content of nano-SiO₂ have increased; sothe damping performances of PUR have been improved. The shape of DMA curves is almost the same, because the nano-SiO₂ particles do not change the proportion of soft sections and hard sections, just change the force between the hard sections.The innovations of the paper: The combination of in-situ polymerization and casting molding, it makes the nano-sized SiO₂ dispersed in the PUR homogeneously; it improves the mechanical properties, heat-resisting properties and dumping proprieties; and predigests the synthesis process.