How to Avoid Post-Extrusion Discoloration in White Polyolefin Films

摘要

The preservation of physical properties and aesthetic appearance are key measures in the film industry. As such, one needs to be selective in choosing the polymer and the stabilization systems used to derive robust and attractive film products. In selected applications, it is desirable to have film products that do not discolor during processing. It is often even more important that the film not discolor while it is kept in storage. It is recognized in the film industry that under a selected set of circumstances, certain types of stabilizers (when exposed to an oxidizing environment) can lead to discoloration. This may be due to several factors, such as: inadequate stabilizer concentrations, harsh processing conditions, improper selection of white pigments (TiO_2), prolonged storage of the films in a environment containing oxides of nitrogen (pollution), and even lengthy exposure to fluorescent lighting. Using a new approach with "phenol free" stabilization systems, we suppressed post extrusion discoloration in clear and white pigmented films. "Phenol free" stabilization is highly recommended for color critical polyolefin film applications. For film applications where it is a logistical challenge to go "phenol free", we have explored the threshold of phenolic AO that can be used, yet still maintain low color.