In-situ polymerization and characterization of poly (ε -caprolactone) urethane/ SiO₂ nanocomposites

Nanocomposites of poly(ε -caprolactone) (PCL) castable polyurethane elastomer (CPUE) with nano-SiO₂ particles of different surface properties were prepared via in-situ polymerization. An electronmechanical universal testing machine, a durometer, a rubber resilience experimental machine, a dynamic-mechanical analyzer, a thermogravimetric analysis and a scanning electron microscope were used to investigate the macro -static/dynamic mechanical properties, micro-dispersed state and thermostability. The results showed that the modulus at 100% and 300%, elongation at break, tensile strength and tear strength of poly(ε -caprolactone) urethane nanocomposites were increased by introducing a certain amount of nano-SiO₂. Especially the tensile strength and tear strength at 100 °C of the PCL CPUE with 5% nano-SiO₂ pretreated by γ-glycidochloropropyl methyl trimethoxy silane (trade name A-187) were 1.50 and 1.94 times than those of the pure PCL CPUE, respectively. The addition of the nano-SiO₂ had little effect on the hardness, but the impact resilience decreased slightly. The loss factor peaks of two nano-SiO₂ polyurethane composites were higher obviously than the pure PCL CPUE and the glass transition temperature (T_g) of the two nano-SiO₂ polyurethane composites increased to higher temperature region. The surface treatment by the optimum silane coupling agent influenced the dispersibility of nano-SiO₂ in the PCL CPUE distinctly. The agglomerating phenomenon, and even some nano-agglomerates with more than 1 μm diameter can be observed in the PCL CPUE with 5% untreated nano-SiO₂, but the nano-SiO₂ pretreated by A-187 was dispersed in the PCL CPUE at nano-scale.