Study Of Structure, Morphology And Properties On Polypropylene/Nylon6 In-situ Fibrillation Composite Under Shear Force

As one of the most important methods to reinforce mechanical properties of polymer, In-situ fibrillation has attracted a great deal of interests. While according to the method of introducing shear force field to induce macromolecular chain orientation is also an important method to improve the mechanical properties of polymer composite. In this paper, by combining in-situ fibrillation with shear force field together to enhance their reinforcement ability, the properties of the composite are expected to increase greatly. Based on such plan, Our purpose in this study was to determine the effect of shear on the fiber orientation and interfacial adhesion in polypropylene/nylon6 fiber composites via dynamic packing injection molding (DPIM) , in which the melt is first injected into the mold and then forced to move repeatedly in a chamber by two pistons that move reversibly with the same frequency as the solidification progressively occurs from the mold wall to the molding core part. SEM, 2d-WAXD, FTIR, DSC and mechanical testing were used to characterize the samples obtained. The main results are as follows:(1) With the content of PA6 increasing from 10% to 40%, effect of fibril enhancement first increased and then decreased. It has been reached an optimum effect about the PA6 content of 20wt%. There are different results of fibril formation with the PA6 content changing. Only when PA6 content is 20wt% or 30wt% in PP/PA6 composites, there shows better PA6 fibril formation and better dispersion in PP matrix. There are different fibril morphologies on the different zones of injection-molded samples. The fibril became thinner and shorter in the core layer of the sample with bad fibril orientation. The PA6 fiber could confine the orientation of PP molecular chain. The orientation of PP chain is almost totally limited at the 30wt% of PA6 content. Combined the morphology of PA6 fibril with PP orientation, an integrative improvement of PP/PA6 fiber composites' properties is achieved when the PA6 content is 20wt%.(2) The addition of CNT takes a little effect on the tensile strength of static specimen. While according to combining the shear force field with CNT, the polo(propylene) and nylon6 fiber take orientation together. Their synergetic effect makes dynamic samples have a better tensile strength than static ones. And the tensile strength first increases and then decreases, that's because High loading of CNTs will cause a decrease of strength because of their brittleness, poor dispersion in the PA6 fibers and poor compatibility with them. The load of CNTs has little influence on the impact strength in static specimens, the increase of impact strength in dynamic specimens attributes to the orientation induced by shearing during dynamic packing injection molding. Besides this, the shear force also makes the CNT expose on the surface of the fiber, and makes the PA6 fiber orient more regularly. By forming interconnection network structure, the conductive properties of the composite increased greatly.