Melt Shear History and Contaminant Catalyzed Scission in Post Consumer Polyolefin Silo Blends
Deactivate metal catalysts and neutralize acid traces with targeted additives to stabilize viscosity drift and optimize landed cost per good recycled part.
Ziegler Natta Catalyst Residue
Meaning
Inorganic remnants of the polymerization catalyst can remain in the finished polymer resin and affect its thermal stability. The presence of ziegler natta catalyst residue can accelerate the oxidation of the polymer chains when the material is heated during melt processing. This reaction leads to a reduction in the molecular weight of the resin and changes its melt flow rate.
Compounders must add stabilizers to neutralize these reactive metal residues.
Polymer Degradation
Titanium and aluminum compounds in the resin act as catalysts for oxidation at high temperatures. When ziegler natta catalyst residue is present, it decomposes hydroperoxides into free radicals.
Equipment Protection
Corrosive acidic compounds can be formed when catalyst remnants react with moisture during extrusion and moulding. While ziegler natta catalyst residue is in the melt, it can release chloride ions that form hydrochloric acid. This acid attacks the polished steel surfaces of injection moulds, causing pits and rust.
This wear destroys the surface quality of the tooling and leads to cosmetic defects on the molded parts. Protecting the tool requires regular cleaning and the application of anti-corrosion coatings.
Compounding Practice
Compounders must select the right additives to neutralize catalyst remnants and prevent polymer degradation. To mitigate the effects of ziegler natta catalyst residue, manufacturers add synthetic hydrotalcites or other acid scavengers to the resin blend. These additives react with the acidic byproducts and trap them within their molecular structure.
This neutralization prevents the breakdown of the polymer during extrusion and subsequent injection moulding runs. It ensures that the resin can be processed safely without damaging the machinery or the finished parts.