Fluoropolymer Processing Aid Dosing Economics under High Shear Profile Tooling
Optimize fluoropolymer dosing between 400 and 800 ppm to balance wall slip against startup induction scrap and avoid masterbatch working capital drag.
Ultra High Molecular Weight Siloxane
Meaning
Silicone based polymer with extremely long molecular chains that provide high durability and specialized surface properties in industrial applications. Using ultra high molecular weight siloxane improves the impact resistance and scratch performance of thermoplastic resins without significantly altering their base mechanical properties. These materials typically exist as gums or masterbatches that are dispersed into a host polymer during compounding.
Their size prevents them from migrating out of the finished part over time.
Tribological Benefit
Reducing the coefficient of friction is the primary reason for adding these polymers to a formulation. The ultra high molecular weight siloxane creates a low energy surface that resists wear and abrasion. Unlike liquid oils, this polymer remains locked within the plastic matrix.
Dispersion Mechanism
Integrating the gum into a rigid resin requires high shear mixing. During the processing of ultra high molecular weight siloxane, the polymer must be broken down into tiny droplets to ensure uniform performance. If the dispersion is poor, the material can form clumps that act as stress concentrators.
Proper screw design in the extruder is essential for achieving a fine morphology.
Rheological Impact
Viscosity of the melt increases when these long chains are present. An ultra high molecular weight siloxane can affect the flow through a die, requiring adjustments to the processing temperature or pressure. This change can be beneficial for stabilizing a melt curtain in film production.
The balance between processing ease and final part performance must be carefully managed.