Study of microstructure, thermal behavior, and mechanical properties of injection molded pa6 microcellular nanocomposites

Microstructure, thermal behavior, and mechanical property of microcellular polyamide 6 (PA6) /montmorillonite (MMT) nanocomposites have been studied. The addition of nanoclay at a proper loading level led to much higher cell densities and smaller cell sizes in microcellular injection molded components and facilitated the formation of small -phase PA-6 crystalline structures. Microcellular PA-6 nanocomposites also possessed higher tensile strengths in comparison with microcellular PA-6 neat resin samples. Microcell wall structure and smoothness were determined by the size of the crystalline structure, which, in turn, were based on the material system and molding conditions. The correlation between cell density and cell size of the materials studied followed an exponential relationship. In the crystallization kinetics study, the Avrami equation and the modified Ozawa equation were used for isothermal and nonisothermal crystallization processes, respectively. The activation energies determined using the Arrhenius relation for isothermal crystallization and the Kissinger method for nonisothermal crystallization agree with each other well. The existence of nanoclay increases the magnitude of the activation energy. Nanocomposite with an optimal amount of nanoclay has a high nucleation activity. Both the nanoclay and the dissolved gas reduced the overall crystallinity of the microcellular injection molded nanocomposite parts. Solid nanocomposite parts, microcellular neat resin parts, and microcellular nanocomposite parts all have lower crystallinity in the core and higher crystallinity near the skin. The collective effect of the dissolved gas and nanoclay is to shorten the molding cycle time greatly.