The Research On Aging Of Polypropylene/Montmorillonite Nanocomposites

Based on pristine montmorillonite (MMT) and two kinds of organophilic-modified montmorillonite (OMMT1, OMMT2), polypropylene/montmorillonite nanocomposites were synthesized successfully by direct melt intercalation techniques. Thermal oxidative aging, thermal oxidative aging kinetics and hygrothermal aging of polypropylene/montmorillonite nanocomposites was especially investigated.The effect of different kinds of and different contents of montmorillonite on the structure of nanocomposites was studied. The X-Ray Diffraction (XRD), Transmission Electron Microscope (TEM) and Fourier Transition Infrared (FTIR) characterization of nanocomposites suggest that the chains of polypropylene have been successfully intercalated into the layers of montmorillonite and the intensities of peaks have become weakened, both of PP/MMT and PP/OMMT1 don't appear conspicuous diffraction peaks, which means exfoliated nanocomposites; The position of the diffraction peak of 0MMT2's 001 profile excursed to left (which means that the distance between layers has broadened), PP/OMMT2 belongs to intercalated nanocomposite. FTIR suggest that both of OMMT1 and OMMT2 can interact with PP strongly.The effect of different kinds of and different contents of montmorillonite on the mechanical properties of nanocomposites was studied. The results show that the tensile strength and impact strength of nanocomposite firstly increases and then decreases with the contents of montmorillonite increase. The mechanical properties of nanocomposites are best when the of content of montmorillonite is 1.5 percent to 4.0 percent.Thermal oxidative aging of polypropylene/montmorillonite nanocomposites was investigated under the condition of 100℃. The results show that incorporation of a small amount of montmorillonite not only can enhance mechanical properties, but also can improve the thermal oxidative aging performance of polymer-matrix dramatically. FTIR, TGA, DSC and surface morphology analysis suggest that the kinds of montmorillonite, the effect of intercalation and the contents of montmorillonite have a little influence on the thermal oxidative aging performance of polypropylene/montmorillonite.Hygrothermal aging of polypropylene/montmorillonite nanocomposites was investigated. The results show that incorporation of a small amount of montmorillonite can improve hygrothermal aging performance of PP-matrix dramatically. The results showed the hygrothermal aging of the composites lied in the combination of thermal degradation,hydrolysis and damage of the interface.Thermal oxidative aging of pure PP and polypropylene/montmorillonite nanocomposites (the content of montmorillonite is 4.0wt%) was studied under the condition of different temperature (100℃, 110℃ and 120℃). The results show that the mechanical properties of materials decrease gradually as aging time lasts and aging temperature improves, comparatively speaking, aging temperature has more influence on the degradation of materials than aging time. And the higher temperature improves, the worse the degradation of materials.At last. Thermal oxidative aging kinetics of polypropylene/montmorillonite nanocomposites was investigated. The results show that Thermal oxidative aging of polypropylene/montmorillonite nanocomposites belongs to the first order reaction. The first order aging kinetic model based on tensile strength data was set up to investigate the anti-aging performance of polypropylene/montmorillonite. It shows that the aging kinetic model demonstrates preferably PP-matrix composites aging process, and kinetic parameters were obtained. The low reaction rates (k) and high activation energy (E_α) is of great benefit to improve the thermal oxidative aging performance of PP-matrix. The higher activation energy, the more sensitivity the aging reaction to temperature.