What is the key to improving the quality of PVC foamed sheet?
Plastic foaming has gone through three processes, namely the formation of bubble nuclei, the expansion of bubble nuclei, and the solidification of bubbles. However, for the PVC foamed sheet to which the chemical foaming agent is added, the expansion of the bubble nucleus plays a decisive role in the quality of the foamed sheet. Since PVC is a linear molecule, its molecular chain is short and its melt strength is low. During the process of bubble expansion into a bubble, the melt is not enough to cover the bubble, and the gas easily overflows and merges into a large bubble, thereby reducing the foamed film. The quality of the material. So, if you want to improve the quality of PVC foam sheet, what is the key? Here we talk about this issue.
If you want to improve the quality of PVC foam sheet, the key lies in improving the melt strength of PVC. Analysis from the processing characteristics of polymer materials: There are many ways to improve the melt strength of PVC, and the most effective way is to add additives to improve the melt strength and reduce the processing temperature. PVC belongs to an amorphous material, and melt strength decreases with the increase of melt temperature. Conversely, the melt strength increases with decreasing melt temperature. Since the cooling effect is limited, it is only an auxiliary function. ACR processing agents all have the effect of improving the melt strength, among which the foaming modifier has the best effect, and the melt strength increases with the increase of the foaming modifier content. Usually, as long as the screw has enough dispersive mixing ability, adding high viscosity foaming modifier will greatly improve the melt strength.