Detailed Explanation of the Core Production Process of PVC Foam Board
Oct 13, 2025
The production of PVC foam boards mainly adopts the extrusion foaming method. Its core process includes several key stages such as material mixing, extrusion plasticizing, foaming shaping and post-treatment.
Mixing process
This is the foundation for ensuring the stability of subsequent production and product quality. Usually, a combination of high-speed hot mixing and low-speed cold mixing is adopted.
High-speed hot mixing: First, solid materials such as PVC resin, stabilizers, and fillers are added to a high-speed mixer. Under the heat generated by high-speed shearing and friction, the material temperature rapidly rises to around 100℃. At this point, liquid raw materials such as plasticizers and lubricants are added, and the mixing continues to reach 110-120℃. This process enables various additives to be evenly coated on the surface of the PVC resin.
Low-speed cold mixing: Immediately put the hot-mixed materials into the cold mixer, add the foaming agent at the same time, and turn on the jacket cooling water to quickly cool the materials to below 40℃. Cold mixing can prevent materials from caking and thermal degradation, and remove excess moisture to obtain loose and uniform dry-mixed materials.
Extrusion foaming and shaping
This is the soul of the entire craftsmanship. The cooled materials are fed into the counter-rotating twin-screw extruder or conical single-screw extruder through the metering and feeding device.
Plasticizing and compression: The material undergoes different temperature ranges (typically from 120 ° C to 180 ° C) in the extruder and is gradually melted and plasticized into a viscous flow state. During this process, the vent holes of the extruder must be closed to prevent the gas from the decomposition of the foaming agent from escaping.
Foaming and skinning: The fully plasticized melt passes through a specially structured foaming die head. The temperature of the machine head is required to be extremely constant (usually 165-185℃), for which an oil heating plate is often covered externally for precise temperature control. The moment the melt leaves the die, the pressure drops sharply. The gases dissolved in the melt become supersaturated rapidly, precipitate and form countless tiny bubble nuclei. The bubbles expand to form pores.
Immediately after, the foamed slab enters the three-roll calender. The temperature of the calendering roller should be controlled between 60 and 75 degrees Celsius. When in contact with the warmer roller surface, the melt on the surface of the sheet is rapidly cooled and compacted, and the surface bubbles are burst, thus forming a hard, smooth and dense skin layer. This is the "skin formation" effect.
Post-processing and molding
The slabs that have been calendered and shaped are further solidified through the cooling conveying section, then uniformly drawn out by the traction machine, and finally cut to a fixed length by the automatic sawing device.
Key process control points
To produce high-quality PVC foam boards, the following key factors must be precisely controlled:
Temperature control: This is the primary condition for successful foaming. If the temperature is too high and foaming occurs prematurely, gas is prone to escape from the barrel, causing the board surface to crack and become rough. When the temperature is too low, the plasticization is poor, the melt strength is insufficient, the board surface is uneven, and even normal foaming cannot be achieved.
Melt pressure: Sufficient melt pressure is the key to ensuring that the gas is fully dissolved in the melt and does not foam prematurely. The screw speed, the lubrication system in the formula, and other factors all directly affect the melt pressure.
Foaming and nucleation balance: The dosage of foaming agent, the type and dosage of foaming regulator (which affects melt strength), and the dispersion status of calcium carbonate (as a nucleation agent) jointly determine the number, size and uniformity of cell structure.
