Polyamide (PA), also known as Nylon, is a clear and printable thermoplastic that has a relatively high melting point, exceptional strength and toughness, and good oxygen barrier properties. It is also scratch, puncture, and flex-crack resistant and does not dissolve/absorb grease, oil, or acidic food. These properties make PA ideal for use in conventional and microwave cooking applications.
The two most popular grades of polyamides are Nylon 6,6 and Nylon 6. Both have the same ratios of carbon, hydrogen, oxygen, and nitrogen, and possess very similar properties. However, there are some differences; under similar processing conditions, Nylon 6,6 is usually more crystalline and more ordered than Nylon 6 resulting in slightly different physical properties such as higher melting point, higher modulus, and slower permeability and moisture absorption, whereas Nylon 6 has somewhat better ductility and impact resistance.
Nylon is ideal for cheese packaging because it has excellent oxygen barrier properties but is carbon dioxide (CO2) permeable, thus if CO2 is formed during storage it will not be trapped inside the package and, thus, does not balloon it.
Compared to other specialty film resins, Nylon is relative easy to process and performs well at both high and low temperatures. It is microwaveable, recyclable, and burns without releasing harmful chemicals to the atmosphere.
The two most common types of Nylon film are cast or unoriented Nylon and
biaxially oriented Nylon (BOPA)1. BOPA is the most important polyamide film. It is an excellent choice for demanding packaging applications.
The orientation results in higher tensile strength, lower elongation (harder to stretch), greater stiffness, and higher oxygen barrier compared to non-oriented cast PA film.
Nylon is often co-extruded with other films such as polyolefins. As a component of a multilayer film, it provides an effective oxygen barrier and improves mechanical strength.
Biaxial Oriented Nylon or BOPA film can be used for a wide variety of applications especially where high gas barrier properties are required. Because of its higher price relative to PVC, PE, and PP film, it is generally considered a specialty film. It is mainly used as a flexible packaging film for food sensitive to oxygen and is chosen when high mechanical strength, high melting point, transparency, and good oxygen barrier is required. Important food packaging applications include processed meat (sausage, bacon), smoked fish, cheese and other diary products, and semi-finished microwavable meals.
The three most important commercial Nylon film types are biaxially orientated film (BOPA), cast mono-film, and multi-layer co-extruded films.
1”Biaxially oriented" means that the PET film is stretched in two different directions to increase strength and modulus (lower elongation and higher stiffness).