What are the differences in process control when co-extruding PVC/PMMA and PVC/ASA profile materials?

What are the differences in process control when co-extruding PVC/PMMA and PVC/ASA profile materials?

The solubility parameters of ASA, PMMA and PVC are very close, and their compatibility is good. The co-extruded layer is not easy to peel off. Generally, the thickness of the co-extruded layer is 0.2 to 0.4 mm. When extruding profiles, single-screw extruders are usually used for co-extrusion. The extrusion temperature of PMMA should be controlled at a relatively high level (generally 210 to 230℃). If the temperature is too low, the melt viscosity will be high, the output will be uneven, and the thickness deviation will be large. However, if it is too high (over 260℃), it will cause overheating decomposition and discoloration. Therefore, the temperature must be strictly controlled. ASA and PMMA have relatively high hygroscopicity and must be thoroughly dried before use. Generally, the drying temperature of ASA should be controlled relatively high. The process control of co-extrusion is shown in the table.