Zhou Nan-qiao

Batch Foam Processing of Polypropylene/Polydimethylsiloxane Blends

Batch foaming processes were employed to prepare plastic foams from polypropylene (PP)/polydimethylsiloxane (PDMS) blends. Various amounts of PDMS were added to a PP matrix, and the resulting blends were batch foamed at different saturation pressures using carbon dioxide (CO2) as the blowing agent. Ultimately, the blend foams exhibited better cell morphologies and higher cell densities in comparison with those prepared from PP alone. The increased solubility of CO2 in PDMS made it as a CO2 reservoir to induce more nucleation. When the PDMS content exceeded a certain level, however, it exerted a negative influence on cell density. Moreover, as the saturation pressure was raised, the cell density of the blend foams increased significantly. It was also noted that the addition of PDMS to the PP matrix generated some very small cells in the larger cell walls.

Study on the Effect of Axial Vibration of Screw in Plasticating Process (Extrusion Part)

To improve the conformation of polymers, axial vibration is offered in the entire polymer process. Two sections, the axial shearing section and the axial pressing section, exert the effects of vibration on the melt. In the axial shearing section, with the effect of vibration, molecular chain orientations in the direction of flow and vibration produce the network frame, which ameliorates the mechanical properties, especially in the transverse direction, of the polymer product. The vibration can promote the disentanglement of molecular chains, which leads to a decrease in the viscosity and an increase in the flowability of melt. At the same time, it can ameliorate the blend quality of the filling system. Some experiments on extruded film, sheet, pipe, foam, and filling systems prove that the analyses are correct.

Study of Vibration Field on Microcellular Foaming in Nucleating Agents

A novel microcellular processing experimental setup was developed in which various nucleation agents were added to foaming material (Polystyrene). The effect of the nucleation agents on cell morphology of foam plastics was studied in the vibration field. The effects of the processing conditions such as nucleating agents, particle size of the nucleating agents, content of the nucleating agents, and the vibration parameters on polystyrene cell morphology were investigated. The cell morphology was analyzed with a scanning electron microscope. The results showed that the samples blown with nucleating agents, in general, had larger cell density and much smaller cell size than the ones without nucleating agents. It is believed that the smaller nucleating agents will be helpful for the larger bubble densities and the smaller cell size. There is the optimum content range for the maximum bubble densities and the minimum average cell diameter in foaming processing with nucleating agents. In the range of vibration parameter, the cell density increases with an increase of frequency and amplitude, and the cell size is the reverse.