The Influence of Epitaxial Crystallization on the Mechanical Properties of Polyamide 66/Reduced Graphene Oxide Nanocomposite Injection Bar

Abstract

Polyamide 66 (PA66) was chosen as the representative of hydrophilic polymers, to investigate the influence of epitaxial crystals in semi-crystalline polymers/reduced graphene oxide nanocomposite injection-molding bars. A differential scanning calorimeter was used, and the two-dimensional wide-angle X-ray diffraction technique, as well as the two-dimensional small angle X-ray scattering technique, were used to research the crystallization behavior in PA66/RGO nanocomposites. The results indicated that RGO was an effective nucleation agent for PA66. The presence of RGO could enhance the orientation degree of the PA66 crystals and did not influence the crystal structure of the PA66. The non-epitaxial crystals and the epitaxial crystals existed in PA66/RGO nanocomposites. The size of epitaxial crystals was much greater than that of the non-epitaxial crystals. Tensile test results showed that the presence of fewer epitaxial crystals can improve the mechanical properties of a polymer.

In Situ SAXS and WAXD Investigations of Polyamide 66/Reduced Graphene Oxide Nanocomposites During Uniaxial Deformation

“…Because of the addition of RGO, the unstretched sample possesses orientation. 20 As can be seen in Figure 3 , the nonuniform diffraction ring of the (010) + (110) lattice plane becomes more focused and the elliptic 2D SAXS signal is stretched during the stretching process. In Figure 4 a, the positions of WAXD peaks do not change, indicating that the crystal form of PA66 is maintained during the elastic deformation process.…”

“…The Lorentz-corrected 1D SAXS curves of pure PA66 only have one slight peak located at the q 2 position ( q 2 peak) throughout the stage I ( Figure 2 b), which accords with our previous work which indicated that the scattering peak of the pure PA66 sample is at q = 0.80 nm –1 . 20 Although we only obtain the partial q 2 peak, its variation trend can be distinguished. With the increase of strain, the peak intensity of the q 2 position continually slightly increases and the q 2 peak slightly moves toward a lower q value.…”

“…In our previous work, we have obtained the PA66/RGO1.0 nanocomposite containing more epitaxial crystals and few non-epitaxial crystals. 20 Therefore, we study the structural evolution of epitaxial crystals in the PA66/RGO1.0 nanocomposite during uniaxial deformation in this section. As shown in Figure 3 , the PA66/RGO1.0 nanocomposite breaks when the strain is about 50%.…”

“…In our previous paper, 20 we have studied the structure and mechanical properties of the PA66/RGO nanocomposite. Because of the existence of H-bonds, RGO more easily absorbs the chains of hydrophilic PA66.…”

A Review of Current Development of Graphene Mechanics

“…Graphene oxide (GO), including reduced graphene oxide (RGO) and thermally reduced GO (TRGO), is typical graphene materials with topological defects in their periodic structures [150,151], shown in Figure 16. GO exhibited an extra Raman peak below the G band (about 1600 cm −1 ) in Figure 16b, which was ascribed to the oxidation of graphite and the subsequent introduction of defects in the graphitic planes.…”