Molecular Dynamics Simulation of the Synergistic Effect of Alkali/Surfactant/Polymer on the Formation and Stabilization of Water-Based Foam Systems

The stable maintenance effect of a chemical oil displacement agent on a foam liquid film usually creates problems with the oilfields surface system. To achieve comprehensive insights into the influence mechanism of these chemical agent components on the foam liquid film, an "SDBS/HPAM/OH^-" water-based foam simulation system and corresponding control systems were constructed by adjusting the categories and quantities of component molecules by molecular dynamics (MD) simulation. The simulated results indicated that the foam stability follows the order of "SDBS/HPAM/OH^-" system > "SDBS/HPAM" system > "SDBS" system. The smaller the inclination angle of the SDBS molecular tail chain, the greater the tendency of the SDBS molecular configuration to be "upright" at the gas-liquid interface, which is not conducive to preventing the aggregation and penetration of gas molecules at the gas-liquid interface. Although the presence of HPAM molecules can significantly enhance the stability of the liquid film by restricting the liquid film's drainage and the diffusion of gas molecules, the addition of HPAM molecules would weaken the formation ability of the foam liquid film. Through decreasing the aggregation of cations around the co-adsorption layer, OH^- not only enhances the interfacial activity of SDBS molecules, but also reduces the electrostatic repulsion between -COO^- groups on the HPAM molecular chain, which makes the foam more stable. With an increase in the pH, SDBS concentration, and HPAM concentration, the stability of foam liquid film was strengthened. These results are helpful in facilitating new insights into the formation and stabilization mechanism of water-based foams. In particular, they provide support for the development and application of new defoaming technologies.

Deformation and Simulation of the Cellular Structure of Foamed Polypropylene Composites

Foamed Polymer is an important polymer material, which is one of the most widely used polymer materials and plays a very important role in the polymer industry. In this work, foamed polypropylene (PP) composites are prepared by injection molding, and the cell deformation process within them is studied by combining visualization technology and COMSOL software simulation. The results shows that the deformation of isolated cells depends in temperature, and there is no macroscopic deformation. There was no significant difference between the stress around adjacent cells at different temperatures, but the stress at different positions around the adjacent cells has obvious changes, and the maximum stress at the center of the adjacent cells was 224.18 N·m^-2, which was easy to cause a lateral deformation of the cells. With the increase in temperature, the displacement around the adjacent cell gradually increased, the maximum displacement of the upper and lower symmetrical points of the cell was 14.62 μm, which is most likely to cause longitudinal deformation of the cell; the deviation of the cell deformation parameter gradually increased, which led to deformation during the growth of the cell easily. The simulation results were consistent with the visualized cell deformation behaviors of the foamed PP composites.

High-Pressure Preform Foam Blow Molding

Recently, several companies have started to use the foaming technology in blow molding processes, primarily in extrusion blow molding. Despite the design complexity involved in the preform blow molding method, substantial advantages result when microcellular foaming and blow molding are combined. In preform and extrusion blow molding, the preform (i. e., the parison) undergoes significant biaxial stress during the inflation stage. Since either extensional or shear stress can dramatically improve cell nucleation, an externally applied stress can cause small-scale, local pressure variations throughout the sample, thus reducing the energy barrier for cell nucleation. So, unlike the current low-pressure foam blow molding technology, where cell nucleation occurs before inflating the preform/parison, we used a high-pressure system to prevent premature foaming in the shaping stage. Consequently, cell nucleation was induced after biaxial stresses were created to induce a higher cell density.