15

2020

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01

The Impact of PVC Heat Stabilizers on Foamed Board Production

　　Before discussing the impact of PVC heat stabilizers on PVC foam boards, let’s first take a closer look at what PVC foam boards are. They are sheet materials with a closed-cell foam structure and are widely used. However, during the manufacturing process, this material often experiences pore rupture. There are many factors that contribute to this phenomenon, one of which is related to the selection and dosage of PVC heat stabilizers.
　　Good melt plasticization is a prerequisite for producing high-quality PVC foam board products. If there are issues with the thermal PVC stabilizer or if the extrusion temperature is too high, local degradation of the melt may easily occur, leading to reduced melt strength and eventual tearing of bubbles due to their excessive size. Conversely, if the extrusion temperature is too low, the melt will remain underplasticized and exhibit very low strength, also resulting in bubble rupture. During the production of PVC foam boards, it is essential to regularly conduct stability tests on the PVC stabilizer at temperatures ranging from 180 to 200 degrees Celsius. Raw materials that fail to meet the stability requirements must not be used—or, if necessary, their dosage should be adjusted—and can only be used after passing the stability test.
　　In addition to ensuring that the melt does not degrade during extrusion, PVC heat stabilizers also have an important function: they regulate the decomposition temperature of the foaming agent. If the amount of PVC heat stabilizer added is too high or too low, causing the foaming agent’s decomposition temperature to be either too low or too high, this will adversely affect foaming.
　　The amount of PVC heat stabilizer should be adjusted according to the grade of resin being used. For instance, when using Type 8 resin—which has a lower plasticization temperature—the dosage of PVC heat stabilizer should be appropriately increased to ensure that the material’s plasticization temperature matches the decomposition temperature of the foaming agent. However, if too much PVC heat stabilizer is added or the melt temperature is too high, the foaming agent may decompose prematurely within the extruder, causing foaming gas to escape through the feed port and vacuum port. On the other hand, if too little PVC heat stabilizer is added or the operating temperature is too low, the foaming process will be incomplete. Therefore, the dosage of PVC heat stabilizer must be carefully optimized.

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