The Difference Between PVC Celuka Foam Board & PVC Free Foam Board

We know that the PVC foaming board can also be called hard PVC microporous foaming material, according to the different production process can be divided into PVC free foaming board and PVC skin foaming board. In fact, it is the difference of extrusion foaming process.

1. Free Foaming (Free - Foaming) : Free Foaming is melt left the mouth mould will be unrestricted free expansion, after a short period of time, and then enter the size bigger sizing system. The Free foaming makes all the bubbles form on the section of the extruder, and the growth of the surface bubbles is limited by cooling. Finally, the continuous density, the surface is moderate hard and smooth products are formed. The advantage of this method is the simple process, suitable for the production of thickness of 2 ~ 6mm, simple geometry, surface gloss products (such as pipe, sheet and simple geometry profile, etc.).

2. Internal foaming method (Inward - foaming) : Crust Foaming method or said luca method (Celuka method). A special mould with a core is adopted to separate the plasticized materials, and the shaping device is connected with the mould. The outer contour is the same as the mould. When the material is sent to the setting sleeve before the mold, the melt containing the blowing agent enters the cooling setting sleeve as soon as it leaves the mouth film and undergoes rapid cooling over the entire surface, thus preventing the formation of surface bubbles and any expansion of the extruder section. It cools on the surface to form a cortex. At the same time, the core inside the mouth mold makes the cavity created in the semi-finished product filled with the foam formed by the rest of the melt, that is, the foam inside. By controlling the cooling strength, the products with surface thickness of 0.1 ~ 10mm and wall thickness of more than 6mm can be obtained. This method can produce the profile with complex section shape, and the product has the characteristics of smooth surface, high hardness and low density in the core area. In addition, by combining the method with method ①, one side of the product is crusted and the other side is free.