Preparation And Properties Of Carbon Nanotubes/Montmorillonite Reinforced Poly (Ether Ether Ketone) Nanocomposites

Poly(ether ether ketone)(PEEK)is an important high-performance semi-crystalline polymer that can be used for long periods up to 250 ?.The addition of nanofillers such as carbon nanotubes(CNTs)is an important means to further enhance its performance.However,since PEEK is insoluble in organic solvents,how to solve the problem of agglomeration of CNTs in PEEK is still a challenge.This paper introduces montmorillonite(MMT)as a second filler to promote the dispersion of CNTs,improve PEEK performance and reduce costs.The main results are as follows:(1)Preparation and properties of PEEK nanocomposites.The CNTs/MMT hybrids were obtained by ultrasonic treatment of the aqueous solution containing CNTs and MMT.The PEEK powder was added to the solution,then stirred,dehydrated and dried to obtain PEEK/CNTs/MMT masterbatch.PEEK/CNTs/MMT nanocomposites with different MMT contents were prepared by melt mixing.The results of the sedimentation experiment and the zeta potential show that the introduction of MMT improves the dispersion stability of CNTs.The CNTs/MMT hybrids were maintained in PEEK nanocomposites as demonstrated by transmission electron microscope(TEM)and scanning electron microscope(SEM).Tensile tests show that the introduction of CNTs and MMT increase the tensile modulus and tensile strength of PEEK,and the elongation at break decreases.Dynamic mechanical analysis(DMA)shows that the storage modulus of PEEK nanocomposites containing 0.5 wt%CNTs and 2 wt%MMT at 240 ? increases by 48.1%compared to pure PEEK.(2)Wide-angle X-ray diffraction(WAXD)was used to observe the structural evolution of PEEK nanocomposites at high temperatures(170.210 and 250 ?).The tensile results show that the addition of nanofillers tends to increase the modulus of the PEEK nanocomposite at each temperature.The WAXD results show that the orientation function decreases at the early stage of stretchincg reflections and then increases again.On the other hand.the intensities of the diffractions get lower and the widths get wider with the proceeding of tensile,indicating that partial crystals are fratured and finer microcrystals are formed.(3)The crystallization behavior of PEEK/CNTs/MMT nanocomposites.The effect of nanofillers on the crystal structure and long period of PEEK was investigated by WAXD and small angle X-ray scattering(SAXS).WAXD results show that the introduction of CNTs and MMT does not change the crystal structure of PEEK.SAXS results reveal that the long period increases with the addition of CNTs while decreases with further addition of MMT.The non-isothermal crystallization behavior the nanocomposites was studied by differential scanning calorimetry(DSC).The results show that CNTs promotes the crystallization of PEEK,and further addition of MMT inhibits the process.The nucleation activity of the fillers was also evaluated by the Dobreva method.