During the foaming process of materials, the gas decomposed by the foaming agent forms bubbles in the melt. There is a trend of small bubbles expanding towards larger bubbles in these bubbles. The size and quantity of bubbles are not only related to the amount of foaming agent added, but also to the strength of the polymer melt. If the intensity is too low, gas can easily escape upon diffusion to the surface of the melt, and small bubbles merge with each other to form large bubbles. The long molecular chains of foaming regulators are entangled and adhered to the molecular chains of PVC, forming a certain network structure. On the one hand, it promotes material plasticization, and on the other hand, it improves the strength of PVC melt, so that the foam cell wall can withstand the pressure of gas inside the foam cell during the foaming process, so as not to rupture due to insufficient strength. Foam regulators can make product pores smaller and more numerous, with a more uniform and reasonable pore structure, greatly reducing the density of the foam body. Poor quality or insufficient dosage of foaming regulators can lead to low strength of the foam, resulting in burst or string bubbles.
The molecular weight and viscosity of foaming regulators produced by different manufacturers vary greatly. When foaming products break or string bubbles, and other methods are ineffective, replacing the foaming regulator or increasing the dosage appropriately can often produce significant effects. However, adding or replacing foaming regulators with higher molecular weights can increase product density due to excessive viscosity, which prevents the expansion of bubbles in the melt. And due to the high viscosity of the melt, the fluidity will deteriorate, resulting in uneven discharge of the mold, affecting the flatness of the plate surface, and even short production time, leading to mold paste failure, especially when producing plates with a thickness of less than 10mm.
Post time: May-24-2024
