Study On Preparation, Structure And Mechanical Properties Of MC Nylon 6/TiO₂ In-situ Nanocomposites

MC nylon 6/TiO2 nanocomposites have been prepared by means of anion in-situ polymerization. The dispersity of nano-TiO2 in nylon 6 was studied by TEM, and the crystallization and melting behavior, structure and mechanical properties of nanocomposites was studied by DSC, XRD and mechanical properties methods. The conclusions as follows:(1). When the nano-TiO2 content <1%, it has a good dispersity. When the nano-TiO2 content >1%, it begin to cluster. Nano-TiO2 doesn't influence on the crystal style of MC nylon 6.(2). The results of isothermal DSC of nylon6 and nanocomposites show that nano-TiO2 influenced the behavior of isothermal crystallization of nylon 6. The results of Avrami equation show that nano-TiO2 were nucleation reagent of nylon 6, which raised the crystallization rate and decreased the half time of isothermal crystallization. The values of Kg of nanocomposites througing Hoffman equation increased with the increase of nano-TiO2 content.(3). The results of non-isothermal DSC of nylon6 and nanocomposites show that nano-TiO2 influenced the behavior of non-isothermal crystallization of nylon 6. The non-isothermal crystallization of nylon 6 and nanocompsoites was analyzed by the methods of Ozawa, Jeziomy and Mo, the results show that the method of Mo is optimal method for nylon 6 and nanocompsoites. The results of the non-isothermal crystallization kinetics show that nano-TiO2 were nucleation reagent of nylon 6, which changed the nucleate mechanism of nylon 6 and increased the crystallization activation energy, indicating the nano-TiO2 baffled the movement of molecular segments of nylon 6.(4). The isothermal and non-isothermal melting behaviors of nylon 6 and nanocomposites have been studied by means of DSC. The results show that the isothermal melting curves have three peaks and non-isothermal melting curves have two peaks. The values of temperature of the low temperature peaks increased and the high temperature peaks invariable, indicating that nano-TiO2 enhanced the perfection of crystal of nylon 6.(5). Nano-TiO2 increased thermal stability of composites and mechanical properties, but decreased elongation at break, which indicate nano-TiO2 has strengthening and toughening ability. The results of UV-irradiation show that the mechanical properties of nylon 6 and nanocomposites decreased with the increase of UV-irradiation time at the beginning, but when the UV-irradiation time is 21 day which leaded to crosslink and made the mechanical properties of nylon 6 and nanocomposites increased. The nanocomposite with 1% TiO2 is the optimal composite to resist UV-irradiation.