Effect of Resin Viscosity on Cell Nucleation and Growth

In this study, resins with different viscosities were prepared by melt blending in an extruder and chemically foamed using an injection molding machine. The nucleation and growth process of the cell was monitored using visual equipment, and the results were analyzed and fitted. The experimental results showed that as the resin viscosity increased, the cell density gradually decreased while the average cell size increased. Higher resin viscosity hindered the diffusion of gas, raising the cell nucleation energy barrier. Furthermore, it delayed the appearance time of cells, reducing a slower formation and growth of cells, leading to uneven cell distribution and a tendency for larger cells to form. In contrast, lower resin viscosity reduced the resistance to nucleation, promoting the formation of more cells at a faster rate and enhancing the growth rate of the cells. The N-t and D-t curves of resins with different viscosities exhibited a “half S” shape. Cells formed and grew rapidly in the early stages of foaming, but both nucleation and growth rates slowed in the later stages, eventually stabilizing.