The permeability of polymers to gases and vapors is crucial for their effectiveness in food packaging. This permeability is influenced by various polymer properties such as free volume, crystallinity, tacticity, cross-linking, orientation, and thickness. These properties determine how well the packaging can prevent moisture loss and block unwanted contaminants, including odors.
Polymers used in food packaging come in various forms, including films and flexible items, as well as rigid containers like clear drink bottles and opaque dairy cartons. Each form serves specific purposes based on the food's needs and the packaging's required durability.
Polyethylene, polypropylene, polystyrene, and polyvinyl chloride are among the most commonly used plastic polymers in food packaging. Each of these polymers offers unique properties that cater to different packaging requirements. For instance, polyethylene is widely used due to its flexibility and strength, while polypropylene provides excellent resistance to chemicals and high temperatures.
A critical aspect of food packaging is preventing the migration of potentially harmful substances from the packaging into the food. Food can diffuse into plastic packaging, enhancing the migration of unreacted monomers and mobile additives. Thus, the selection of polymers is vital to ensure food safety.
Two of the most important barrier polymers in food packaging are polyvinylidene chloride and ethylene vinyl alcohol. These materials provide exceptional barrier properties, making them ideal for protecting food from moisture and gas transmission. While other materials also play significant roles, these two polymers are indispensable in modern food packaging, ensuring food remains fresh and safe from production to consumption.
Essential Polymers in Modern Food Packaging
