Study On The Confined Crystallization Behavior Of PA6 And Its Effect On The Properties Of Composite Materials

The aggregation state of the polymer has great influence to its performance,especially the semi-crystalline polymer of PA6. The phase structure and phase behavior of restricted polymer has many differences with unrestricted polymer. In this paper, PA6/LiCl composites, PA6/layered silicate clay nano-composites and PA6/layered silicate clay/LiCl composites were prepared respectively by melting extrusion.The complexing restricted mechanism and effect of complexing restricted on the properties of composites were researched by adding complexing agent and inorganic filler. By the way, the dispersing mechanism of layered clay and the effect of layered clay on the crystallization behavior and rheological properties of PA6 were studied. At last, crystallization behavior and performs of PA6 were researched when complexation and layered clay simultaneously exist. The main research content was as follows:First of all, different concentration of LiCl was used to modify PA6. The effect of water absorption on the confined crystallization mechanism and rheological properties of PA6/LiCI composites was performed by Fourier infrared(FT-IR), X-ray photoelectron spectroscopy(XPS), dynamic rheometer, differential scanning calorimetry(DSC), wide-angle X-ray diffraction(XRD) characterization methods.Results show that Li+ can ligand with oxygen atoms, Cl- and N-H bonds form hydrogen bond, which destroyed the hydrogen bonding between PA6 molecules.When the content of LiCl was 6%, LiCl/PA6 composites have been rendered amorphous state. When LiCl/PA6 composites absorbed water, the complexation between LiCl and PA6 was damaged. The crystallinity of composites was higher.However,the tensile strength and impact strength were decreased, when the absorbing water treatment of samples had been dried.Secondly, the method of solution was used and orthogonal experiment was designed to organic modification of hectorite. Then PA6/organic hectorite composites and PA6/organic montmorillonite(OMMT) composites were prepared by melt extrusion method. The effect of hectorite and OMMT content on the properties ofPA6/layer clay composites had been researched. The dispersing mechanism of layered clay was discussed as well. Results showed that, the crystallinity of organic hectorite/PA6 composites and OMMT/PA6 composites were decreased with the increase of clay content. The initial crystallization temperature of layer clay/PA6 composites was less than pure PA6. However the crystallinity of organic hectorite/PA6 composites dropped more apparently. It indicated that hectorite in the PA6 have not acted as the nucleating agent. The layer of hectorite restricted PA6 molecular chain and confined crystallization of PA6. The tensile strength and bending strength of layer clay/PA6 composites were higher than pure PA6, but tensile strength and bending strength of organic hectorite/PA6 composites increase more obviously.Finally, fixed LiCl content was 3%, different content of organic hectorite,OMMT were added to PA6/LiCl composites, respectively. The effect of different clay and complexation on the properties of PA6 composites were discussed by crystallization properties, rheological properties, scattered distribution, and mechanical property. Results showed that the crystallization temperature(Tc) and crystallinity(?Xc) of LiCl/hectorite/PA6 composites first increaseed then decreased with the increase of hectorite content. When the content of hectorite was 5%, the?Xc and Tc was largest, but smaller than the content of hectorite was 0%, which suggested that the hectorite and LiCl had played a synergy in the limited crystallization of PA6. However, the Tc and ?Xc of LiCl/OMMT/PA6 composites were first decreased then increased with the increase of OMMT content. The minimum was reached when OMMT content was 5%. In addition, the movement of molecular chain was restricted and flow resistance in LiCl/PA6/layered clay composites with the increase of hectorite content, so that the G? was increased. But the G?? of LiCl/hectorite/PA6 composites were higher than LiCl/PA6 composites, and the G?? of LiCl/OMMT/PA6 composites were smaller than LiCl/PA6 composites.