Polyolefin Non Intentionally Added Substances Identification Basics
Polyolefin non-intentionally added substances require chromatographic screening, Cramer toxicological tiering, and finished article migration verification.
Ziegler-Natta Catalyst Residues
Meaning
Trace metallic remnants from the polymerization process stay within the finished resin and can influence its long term stability. These ziegler-natta catalyst residues typically consist of titanium and magnesium compounds that were not fully removed after the polymer chains were formed. While modern high yield processes reduce these levels significantly, even minute concentrations can affect the color and chemical resistance of a moulded part.
Thermal Influence
Metal ions act as pro-oxidants when the polymer is heated during subsequent conversion steps. The presence of ziegler-natta catalyst residues can accelerate the breakdown of the polymer during injection moulding, leading to a loss of molecular weight and reduced impact strength. This degradation is often accompanied by yellowing or the development of a distinct chemical odor as the polymer chains fragment.
Tooling Maintenance
Acidic components within the catalyst system can lead to the gradual pitting of steel moulds and extrusion dies. If the ziegler-natta catalyst residues are not properly neutralized with acid scavengers, they can release hydrochloric acid when exposed to moisture or heat. This corrosive effect is most visible on highly polished surfaces where even minor etching results in a loss of part gloss and requires frequent tool refurbishing.
These maintenance costs can escalate quickly if the corrosive residues are allowed to build up over multiple production cycles, affecting the overall return on investment for the project.
Optical Property
Fine particles of inorganic material can scatter light and reduce the transparency of thin films or clear moulded parts. In applications where high clarity is required, the level of ziegler-natta catalyst residues must be kept at a minimum to prevent haze. Resin manufacturers often specify these residue levels in parts per million to help processors select the right grade for optical components or medical packaging.