Study On Reinforced Antistatic PA11/T-ZnOw Composites

In order to overcome the bad mechanical properties of traditional anti- static composites, Tetrapod-shaped ZnO whisker (T-ZnOw), a kind of semiconductor, was used as the antistatic filler and to enhance the mechanical properties of the composites profiting from its unique three dimensional needlelike shapes and its high modulus and strength. In this dissertation, polyamide 11 (PA11)/T-ZnOw composites were produced by extruding mixture and their crystallization behaviors, Rheological behaviors, mechanical properties and electrical properties were investigated by differential scanning calorimetry (DSC), wide angle X-ray diffraction(WAXD), polarized optical microscopy, scanning electron microscopy and capillary rheometer.The analysis of isothermal crystallization behavior indicated that the Avrami equation can perfectly describe the isothermal crystallization of nylon 11 and its composites. The T-ZnOw serves as nucleating agent and increases the crystallization rate of the composites. The mode of the nucleation and growth of nylon 11 and its composites may be two-dimensional and three dimensional space extension. The equilibrium melting point of PA11/T-ZnOw composites obtained by the Hoffman-Weeks theory is higher than that of neat PA11. All the isothermally crystallized samples exhibit double melting endotherms at higher crystallization temperature and triple melting endotherms at lower crystallization temperature.The investigation of non-isothermal crystallization showed that Ozawa equation is not sutibale to describe the non-isothermal crystallization process, while the modified Avrami and Mo equations take great advantages over treating the non-isothermal crystallization kinetics. The incorporation of T-ZnOw into PA11 not only increases the crystallization rate of PA11 in the composites, but also changes the mechanism of nucleation and the growth of PA11 crystallites. All the isothermally crystallized samples exhibit single melting endotherm or double melting endotherms and the incorporation of T-ZnOw promotes the formation of single melting endotherm. The Hoffman-Lauritzen theory and its deduction reveal that the addition of T-ZnOw increases the folding surface free energy and the absolute values of effective activation energy indicating that T-ZnOw restricts the movement of chain segments.The results of POM (Polarized Optical Microscopy) showed that the domain of nylon 11 spherulites decreased while the number of nylon 11 spherulites increased in the composites. WAXD revealed that the incorporation of T-ZnOw did not change the crystalline forms of PA11 in the composites but few T-ZnOw could induceδform of PA11.The experimental research results of rheological behaviors revealed that both PA11 and its composites are pseudo-plasticity fluid. The fact that the non-Newtonian exponents of composites are higher than that of PA11 indicated that the composites are less sensitive to the shear rate. At the same shear rate, the apparent viscosity increased initiately and then decreased with the increasing content of T-ZnOw. The coated T-ZnOw could reduce the apparent viscosity of the composites. The flow activation energy for composites is higher than that for pure PA11, which is indicated that the flow activation energy of composites is more sensitive to the temperature.It was found that the coated T-ZnOw take advantages over enhancing the mechanical properties of the composites but disadvantages over reducing the electrical property of the composites. With the increasing load of T-ZnOw, the mechanical properties of all materials increased initiately and then decreased. In comparison with pure PA11, the tensile strength, normal temperature impact strength, low temperature impact strength, flexural strength and flexural yield strength increase 15.7%, 281%, 60.4%, 19.1% and 32.1% when the addition of T-ZnOw is 15, 8, 3, 10 and 8 share, respectively. The surface resistance and volume resistance of composites reduced to 1×10¹²Î©and 1×10¹²Î©as the T-ZnOw content is 8 shear and 5 shear, respectively.