What is the Direct Foaming Method of PVC Foam Board?

PVC foam board is also called Chevron board and Andy board. According to the production process, appearance and performance, it can be divided into PVC skinned foam board and free foam board. The information compiled for everyone today is related to the foaming method of foamed boards. Let's take a look together. PVC foam sheet can have the properties of sound insulation, sound absorption, heat insulation, heat preservation, etc., mainly because the surface of the PVC crust and semi-skinned foam sheet produced by the foaming technology of the PVC sheet is not only flat and smooth, but also has a high skin Hardness and stiffness, mechanical properties of wallpaper accessories are significantly better than free foam. Foam molding is divided into three processes. Formation of bubble nuclei, expansion of bubble nuclei, and solidification of bubbles. For the PVC foam board with chemical foaming agent, the expansion of the bubble core has a decisive influence on the quality of the foam board. During the bubble core expansion process, the melt is not enough to cover the bubbles, and the gas easily overflows and merges into large bubbles, which will reduce the product quality of the foamed sheet. This article focuses on the direct foaming method of PVC sheet, so that everyone has a comprehensive understanding of the direct foaming method. PVC foaming is also affected by the following factors, mainly the degree of supersaturation of the gas dissolved in the melt, the evaporation heat of the foaming agent and the gas pressure, and the melt viscosity due to the presence of the foaming agent at the same temperature Decrease. The uniformity of the foaming agent and melt mixture, the amount of nucleating agent, particle size, distribution and efficacy, and the solubility of the foaming agent in the melt affect the foaming of PVC sheet.

Which two processes are used to form the direct foaming method of PVC foam board?

The direct foaming method of PVC foam board is mainly formed by two processes, one is a free foaming process method, and the other is a controllable foaming process method. For free foaming, after the melt containing the foaming agent leaves the die, it begins to expand freely within a certain distance from the die, and obtains the desired shape and the foamed product required by the foaming density through the setting device. The density of the foam product is approximately the same in cross section, and the periphery is surrounded by a dense but thin outer skin. Pipes, plates, and profiles can be formed by free foaming under suitable process conditions. At present, it is more consistent that the application of the free foaming method is often limited to products with smaller cross sections, mainly thin-walled parts. For the controllable foaming method, the shaping device is directly connected to the die mouth, and its outer contour is the same as the die. As a result of this type of setting, the melt containing the blowing agent leaves the die as soon as the entire surface of the extrudate is rapidly cooled, preventing the formation of surface cells and the cross section of the extrudate. Swelling of any form factor. At the same time, the cavity generated by the mold core in the die mouth is filled by the cells formed by the melt during the setting process. The density of this foam product varies greatly in cross section, the core density is low, and the outer surface layer density is high. This method can also produce pipes, plates and profiles, and the strength structure is better than free foaming, so it is often used to produce PVC low foaming structural materials that meet different requirements, and the controlled foaming allows the cross-sectional area of PVC products Bigger. The above is an introduction to the foaming method of foamed board. I hope it will be helpful to everyone.