Discoloration Resistant Polyolefin Films

The preservation of physical properties and aesthetics are two important aspects of the film industry. As such, forethought and care need to be taken in terms of the type of polymer and stabilization systems that are used to derive robust and attractive film products. For most applications, a combination of a phenolic antioxidant and a phosphite melt processing stabilizer can provide the base stabilization that is necessary to provide the retention of physical properties, good processability, long term thermal stability without compromising the overall aesthetic appearance of the film product. However, in selected end-use applications, it is very desirable to have film products that do not discolor during initial processing or while the product is kept in storage. Under a selected set of circumstances, certain types of phenolics have been shown to be susceptible to discoloration, either due to inadequate stabilizer concentrations, harsh processing conditions, ionizing radiation, prolonged storage of the films in an environment containing oxides of nitrogen (pollution), or a combination of these factors. Approaches to eliminate discoloration, by using “phenol” and “phenol-free” stabilization systems will be discussed. “Phenol-free” stabilization systems are recommended for color critical polyolefin film applications.