We are able to use fresh food products which are prepared so many days back. It is possible due to development in packaging. We are in the age of synthetic polymer packaging. Plastic packaging has taken the place of traditional packaging. To bring advancement in packaging different types of plastics are combined to make a single entity called multilayered plastic.
In multi layered plastic various density of plastics are compressed to make a single entity. Also other materials like aluminium, paper are also used with plastics. It produces thinner, lighter and compact package reducing total amount of material used. A single layer of plastic can’t fulfill all the requirements. But multilayered plastic combines properties of each monolayer. Its functions are
- It enhances strength and seal-ability of packaging.
- It gives protection or preservation (moisture, gas, light, flavor/odor barrier).
- It increases machinability (tensile strength, softening, slip, rigidity, pliability and heat resistance).
- Its main advantage is its promotion and convenience, cost effectiveness.
In other word it is a single packing structure with multiple functional properties.
It is prepared both in conventional and advanced method. Under conventional multilayered film technique co-extrusion, lamination, coating, co-injection with stretch blow molding, nano technology are included. Under advanced multilayered film technique, surface modification using ultraviolet curing technology, atomic layer deposition, and surface modification of polymers using atmospheric cold plasma method are involved.
On the basis of degree of flexibility multiple layer package are of two types i.e. flexible package film (i.e. film) and semigrid package (i.e. beverage cartoons, multilayer bottles).
On the basis of more than 50% polymer content the GVM (Association of Packaging Market Research) divides multilayer packages into five categories. They are
- Flexible polymer composites without barrier layer
- Flexible polymer composites with barrier layer
- Flexible polymer composites with metal oxide coatings (AlOx or SiOx)
- Thermoformed plastic
- Plastic composites with Al foil
The fundamental constituents of most MLP is polyolefin i.e. polyethylene (PE) or polypropylene (PP). But it gives poor barrier for oxygen, flavor and aroma. Polyamide gives excellent barrier to oxygen, flavor and aroma.
There are mainly 3 to 12 layers present in multilayer packaging. In case of food packaging 3 to 7 layers are present.
Multi plastic are using widely in food packaging industry. In case of two layer one is inner layer and another is outer layer. The polymer present in inner layer do not react with food, is of good sealability at lower temperature. The outer layer gives mechanical strength and printability beside barrier function. In case of three layer an extra layer is present in between these two layers. It provides barrier and it acts as an adhesive layer for two different types of polymer.
After having so many advantages its nonbiodegradable nature makes it our foe. As there are no alternatives available its use is the only option. But it can use as fuel in cement industries, for road construction after discarded. So in various countries producers take back MLP waste under EPR. Research is going on advancement of eco-friendly multilayer plastic packaging.