ACR processing aids can promote the melting of PVC, improve the surface finish, improve the elasticity of the melt, and enhance the elongation and strength of the melt. It helps to cover the air bubbles and prevent them from collapsing. The molecular weight and the amount of the foaming modifier have a great influence on the density of the foamed tablet: With the increase of the molecular weight, the PVC melt strength is increased, the density of the foamed tablet can be made lower, and the amount of the modifier is increased. Have the same effect. However, this effect does not have a linear relationship. To continue to increase the molecular weight or increase the dosage, the effect on the density reduction is not very obvious, and the density will tend to be constant.
There is an important relationship between the foaming regulator and the foaming agent. There is a balance between the density of the foamed sheet and the foaming regulator. Outside of this equilibrium point, the foamed sheet density is not affected by the foaming agent content. Maintaining constant, that is, increasing the amount of blowing agent does not reduce the density. The reason for this is that the melt strength of PVC is limited at a certain amount of foaming modifier, and excessive gas causes the collapse of the cells or merge.