PS Foamed Extrusion Tooling

Introduction to PS Foamed Extrusion Tooling
PS is divided into GPPS and HIPS. Both are members of the polystyrene family, but general-purpose polystyrene (GPPS) and high-impact polystyrene (HIPS) have different applications due to fundamental structural differences. GPPS excels in foaming, while HIPS excels in surface co-extrusion.

Problems and Solutions in Continuous Extrusion Foaming Production of PS

I. Large Cell Size or High Open Cell Ratio
This manifests as uneven cell size and low closed cell ratio in the product, affecting thermal insulation and mechanical properties. It is mainly caused by poor dispersion of the foaming agent or insufficient melt strength, and unreasonable die pressure design. Solutions include: optimizing the screw assembly, adding a shear mixing section to ensure sufficient dissolution of the foaming agent; appropriately reducing the die head temperature (to 115-125℃) to increase melt viscosity; adding a small amount of talc to promote the formation of microbubble nuclei. If the problem persists, it is necessary to replace the front plates of the die head to increase the pressure of the PS Foamed Extrusion Tooling.

II. Orange Peel Surface
This is caused by melt rupture at the die exit or uncontrolled foam expansion. Solutions:
1. Reducing traction speed to match foam expansion with traction stretching; increasing die temperature to improve surface flowability; checking die lip finish, polishing regularly, and removing accumulated material.**

2. Thickness and Density Fluctuations:** Unstable extruder operation leading to fluctuations in extrusion volume or uneven cooling and setting.
3. Using a precise melt pump to ensure stable pressure and flow; implementing zoned temperature control in the setting and cooling water channels, keeping the temperature difference within ±1℃.

3. Die Blockage or Material Adhesion:** Localized carbonization of the melt within the PS Foamed Extrusion Tooling die, or foaming agent precipitation and scaling.
4. Troubleshooting:** Thoroughly cleaning the die and cooling section during shutdown; appropriately increasing the die head pressure to prevent premature vaporization of the foaming agent within the die; if severe, consider adjusting the formulation to increase external lubrication by 0.1-0.2 kg.

5. Uncontrolled Product Warpage and Shrinkage:** Uneven cooling in the PS Foamed Extrusion Tooling leads to internal stress. The cooling water temperature gradient should be adjusted (decreasing from high to low temperature), and the length of the cooling section should be extended. The side that bends is where the cooling is too good; therefore, the cooling of that side should be strengthened.

Our company has 27 years of technical experience. If you have any technical questions, please feel free to contact AONA TOOLING. Our professional engineers will do their best to solve them for you.