Study On The Interfacial Crystalline Morphology Of PA66Nanofiber/iPP Composites

This study is mainly about the interfacial crystalline morphology of polymer nanofiber reinforced isotactic polypropylene (iPP). It contains three aspects:first, polymer nanofibers were prepared through electrospinning technique and the collection setup and processing parameters were varied to change the arrangement and morphology of the as-electrospun nanofibers; second, the nylon66(PA66) nanofiber/iPP composites were prepared through isothermal solution crystallization and finally, the kinetic of the transcrystallization induced by PA66nanofiber bundle was studied. In addition, the iPP matrixes with different molecular weight were adopt to study the effect of matrix molecular weight on the transcrystallization kinetics.The results of this study have shown that:1. By varying the collection setup, the pattern of the PA66nanofiber arrangement could be changed a lot, e.g. the nanofibers were randomly arranged when the stainless aluminum plate was used as the collection setup, but the nanofibers would arranged as a bundle when the rotation needle as the collection setup. In addition, when the roller was adopted, the well aligned nanofibers pat would be achieved. Through changing the electrospinning voltage, the morphology of the as-electrospun nanofibers can be modified. Furthermore, only the voltage higher than a certain value can the PA66solution be electrospun into nanofibers. Though the productivity of the nanofibers was very low, the problem of polymer solution storage should be considered. If the solution was stored too long, the as-electrospun nanofibers were easier to bifurcate and stick to the others and these phenomenons can influence the usage of nanofibers.2. Glass slide was adopted to collect the as-electrospun nanofibers. Then, dip the glass slide into the iPP solution. After several minutes, the glass slide was taken out and a structure called "nano-hybrid shish-kebab" could be detected. The PA66nanofiber served as the "shish" and the iPP lamellae acted as "kebab" in the nano-hybrid shish-kebab. By varying the concentration of the iPP solution, the morphology of iPP lamellae could be changed a lot which is much wider than that prepared with carbon nanotube as the shish. In addition, the morphology of the iPP lamellae could be changed by varying the crystallization time and temperature.3. Through changing the collection method, PA66nanofiber bundle could be prepared. The nanofiber bundle was introduced into the iPP melt and the interface of the nanofiber bundle and iPP matrix was observed by polarized optical microscopy. In the presence of PA66nanofibre bundle, the heterogeneous nucleation distinctly happened in iPP melts and a layer of transcrystalline was developed. Moreover, to reveal the effect of matrix molecular weight on the kinetics of the transcrystallinity, three kinds of iPPs with different molecular weight were adopted. It was found that the higher the iPP Mn, the denser the nuclei. Both a decrease in matrix Mn and an increase in isothermal crystallization temperature led to an increase in the induction time. The maximum temperature (Tmax) at which the transcrystalline layer can be optically observed increased with the increase of Mn. The growth rate of transcrystallinity decreased with increasing Mn and crystallization temperature. Moreover, selective melting of the transcrystalline layers confirmed that it was merely composed of a form crystal for all composites.