The molding of PVC foam board is divided into three processes: formation of bubble core, expansion of bubble core and curing of foam body. For the PVC foamed sheet with chemical foaming agent added, the expansion of the bubble core has a decisive influence on the quality of the foamed sheet. PVC is a straight-chain molecule with short molecular chains and low melt strength. During the process of bubble core expansion into bubbles, the melt is not enough to cover the bubbles, and the gas is easy to overflow and merge into large bubbles, reducing the product quality of the foamed sheet. .
The key factor to improve the quality of PVC foam board is to improve the melt strength of PVC. From the analysis of the processing characteristics of polymer materials, there are many ways to improve the melt strength of PVC, but the most effective way is to add additives that improve the melt strength and reduce the processing temperature. PVC is an amorphous material, and the melt strength decreases with the increase of the melt temperature. On the contrary, the melt strength increases with the decrease of the melt temperature, but the cooling effect is limited and only plays an auxiliary role. ACR processing agents all have the effect of improving melt strength, among which foaming regulators are the most effective. Melt strength increases with increasing foam regulator content. Generally speaking, as long as the screw has sufficient dispersing and mixing ability, adding a high-viscosity foaming regulator has a more obvious effect on improving the melt strength.