Important Formulation Components
Additives are an important part of the formulation of virgin and specialty plastic compounds during the "first life" of the plastic. For example, antioxidants and stabilizers protect polymers from degradation during processing and end use. Every time a plastic material is melted or modified (undergoes a "heating process"), some of the degradation protection additives are consumed. While some antioxidants may remain in the post-industrial or post-consumer recycled (PIR/PCR) material, they may not be sufficient to protect the polymer, which can lead to problems such as gels, black spots, discoloration, changes in viscosity, and poor performance.
These problems can result in wasted material in the next processing step, for example, gels can cause the film web to break down, making post-industrial or post-consumer recycled materials unusable for certain applications. In some types of polymers, additives can help repair the damage (e.g., chain extenders for polycondensates can act on materials such as PET and polyamides). However, in polyolefins such as polyethylene (PE) and polypropylene (PP), the key is to prevent this degradation from occurring.
Processing Aids
Polymer processing aids (PPAs) are commonly used in compounds for blown or cast films, especially LLDPE, to reduce melt breakage in the film (i.e., sharkskin phenomenon) and to prevent material buildup on the mold.PPAs also reduce die head pressure and lower energy consumption. Traditionally, these PPA additives have been based on fluoropolymers as their base structure. Regulators in the European Union and the United States have included such fluoropolymers in the category of perfluoroalkyl substances (PFAS) and polyfluoroalkyl substances (PFAS), and they may be restricted as a result. A number of states in the US have rules in place and regulations with broader coverage are currently under discussion.
Additive and masterbatch suppliers have recently introduced PFAS-free PPAs that are not based on fluoropolymers. Reports indicate that some of the new PPA additives have been shown to eliminate melt breakage faster than traditional fluoropolymer PPAs. In response to the European Chemicals Agency's classification of short-chain oligomers in siloxanes as substances of very high concern (SVHC), suppliers have also introduced siloxane-free processing aids.