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Firstly, the use of PVC processing aid can promote uniform plasticization of the melt and optimize the foaming foundation. PVC processing aid, such as acrylic processing aid, can accelerate the plasticization of PVC melt, forming a uniform and highly elastic melt, avoiding uneven plasticization that may cause cell rupture or collapse. The strength of the melt is improved, and additives such as acrylic processing aid can increase the viscoelasticity and ductility of the melt, allowing bubbles to resist external stress during the expansion stage (when the foaming agent decomposes and produces gas), preventing cell merging or collapse, and forming independent and uniform closed cell structures.

Secondly, control the decomposition of foaming agent and gas diffusion. PVC processing aid can adjust the decomposition temperature of AC foaming agents (usually 160-200 ℃) to synchronize with the optimal viscosity stage of PVC melt, avoiding premature release of gas (causing coarse pores) or too late release (gas cannot fully expand). PVC processing aid improve melt flowability, assist in uniform gas dispersion, and reduce the formation of large bubbles or voids due to local aggregation.

In addition, PVC processing aid can enhance the melt strength, keep the cell walls stable during expansion, reduce gas escape and cell merging, thereby obtaining small and dense cells (such as an ideal structure with an average pore size of 50-200 μ m). High melt strength can prevent the collapse of bubbles or uneven surfaces caused by shrinkage during the cooling stage of the product.

As mentioned above, acylic processing aid, as a classic additive, can accelerate plasticization and stabilize foam pores; The dosage of foaming agent is usually 0.5-2phr, which is combined with acrylic processing aid (1-5phr) to achieve balanced foaming. An appropriate amount of internal lubricant (such as calcium stearate) can further balance the fluidity of the melt and avoid hindering bubble expansion due to high viscosity.