Dislike rigid packaging which is from the materials such as cardboard and carton for packaging, there is another type of packaging used soft materials with very low thicknesses, called flexible packaging.
This type of packaging is used for packing the foodstuff with expiration date, and packaging shall help maintenance of products.
In flexible packaging, the materials such as types of plastic, aluminum and paper films are used. These materials are used in single layer, and sometimes they are stuck in the form of several layers which is called laminate. Thickness of these films could be from less than 10 micron to more than one hundred micron.
To print on these materials, flexography and/or graver printing is usually used. Whereas the foodstuff shall be avoided to be touched with ink layer directly, in this type of printing, a method is used which is called printing on rear side or printing from inside. In this method, the design is printed reversely on a transparent film, then this film is laminated with another film, and the inked layer is placed among two films, hence it prevents direct contact of foodstuff with ink.
The most varied layer in combination of package wrapping are polymer films which are as follows in respect of plentitude and application:
Polyethylene Film: This film is the most commonly used film in packaging industry due to its to be sewed and vicinity with food and medicines, and they are produced and used in transparent and colored forms. This film is also placed in laminated form in the structure of packages, as a layer of sewing and contact, and in single-layer form, it is used for packaging variable products. The internal layer of pockets of milk and fruit juices and shopping bags etc., all are in this group.
Polypropylene Films: This group of films are provided in the directed form (BOPP), in some forms: transparent, metalize, shell and opaque or in the form of cast without cover (SPP) which is mostly clear. The bags such as: grains, cookies and biscuits are from this group. This group of films is the most appropriate films due to its ability to be printed in the industry of printing and packaging.
Polyester film: Polyester film whose commercial name is polyethylene phthalate is the most widely used films in the industry of producing bags because of the features such as transparency, high thermal resistance, high tensile resistance, relative impermeability and low thickness. Application of this film besides aluminum foil generates a number of privileges including increasing shelf life, static, loading ability etc. in producing bags and food packaging.