Nylon 6 (PA6) is a widely used engineering plastic. However, its poor toughness limits its applications. Therefore, toughening PA6 has been a point of interest in the field of PA6 modification. Generally, toughening a plastic with an elastomer reduces the stiffness and heat distortion temperature of the matrix. It has been an important goal of polymer researchers to find a way of toughening PA6 without reductions in its stiffness and heat distortion temperature. In this study, a new kind of material-an ultrafine, fully vulcanized acrylate powdered rubber (UFAPR)-was used to toughen PA6 through melt blending. The influence of UFAPR on the isothermal crystallization kinetics and nonisothermal crystallization behavior of PA was studied with differential scanning calorimetry. The results showed that, with the addition of a little UFAPR, the crystallization rate of PA could be increased, the crystallization temperature could be augmented, and the crystal size distribution of the crystal grain could be narrowed. The changes in the free energy perpendicular to the crystal nucleus were consistent with the results of an Avrami equation according to the theory of Hoffman. The unit surface free energy of the radially developing crystal spherulites decreased with an increasing amount of UFAPR. The results for the mechanical properties, crystalline structure, and crystallization kinetics of PA6/UFAPR composites showed that UFAPR was not only a good toughening agent for PA6 but also an excellent nucleation agent for PA6.
The key for gel-casting is the preparation of ceramic aqueous slurries with excellent rheological properties. The effect of ammonium polyacrylate and pre-oxidation on rheological properties of Si3N4 slurries was investigated. The Si3N4 isoelectric point (IEP) is between 3 and 4 in premix solution and particle surface potential is maximum at pH between 9.5 and 10.5. PAA-NH4 of dispersant can obviously decrease the viscosity of Si3N4 slurries, and the optimal dosage is about 1.6wt% of Si3N4 powders. Meanwhile, the Si3N4 slurries exhibit pseudoplastic fluid with the characteristic of shear-thinning behavior. Due to the improvement of powder surface characteristic, the pre-oxidation significantly improve the rheological properties of the Si3N4 slurries.
The microstructure and dielectric properties of the graphene–epoxy composites prepared by cryomilling at liquid nitrogen temperature were studied by SEM and RF impedance material analyzer. The result indicated that both the dielectric constant and conductivity of the composites increased with the increase of the graphene content. The value of the dielectric constant of the composite with about 8 wt % of graphene was as high as 200. Moreover, the frequency dispersion behaviors of the conductivity within a certain frequency range accorded with the Jonscher's power law demonstrating that the conductive mechanism is hopping conduction. The negative reactance decreased with the increase of the testing frequency which indicated a capacitive character
M-type barium ferrite (BaFel2O19) receives much attention due to the remarkable properties of the bulk materials: large magnetic anisotropy, sufficient saturation magnetization, non-toxic, excellent chemical stability and good corrosion resistivity. Using stoichiometric amounts of iron nitrate, barium nitrate and sodium hydroxide as the starting materials, we have prepared BaFel2O19 by hydrothermal synthesis method. The results show that when the n (Fe3+)/n (Ba2+) ratio of 6 and n (OH−)/n (NO3−) ratio of 2, the morphology of BaFe12O19 is hexagonal platelets which approximately 800 nm in length and 50 nm in thickness. The coercivity of BaFe12O19 is 1286 Oe and the saturation magnetization is 23.7 emu/g. The BaFe12O19/phenolic resin composite has been prepared and the permeability of the BaFel2O19/phenolic resin composite was measured.
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