Paindlikuks pakendamiseks kasutatud materjalid should be safe from different points of view. Food is not allowed to be in contact with external contaminant like bacteria, viruses, other microorganisms, dirt, so the microstructure of the package materials must not allow this dangers to pass through and contaminate food.
Polüpropüleenil on võrkjas kristalliline struktuur, mida kasutatakse ahea barjäär gaasi ja saasteainete eest. So the polymers of polypropylene are widely used in food packaging, conferring a good protection. But some migrants could pierce the macromolecular structure of polymers and could contaminate the food stuff. Such migrants could be mainly the components of printing inks and of polyurethane adhesives.
Polüuretaanliimid are a mixture of two polymers that reacts as temperatures around 30 to 50 degrees celsius. These two components suffer a polymerization process, and it strengthens.
Niisiis, seda liimi kasutataksetrükitud polümeeri sidumine metalliseeritud polümeeriga.It is known that for package food in wraps, and bags, are used laminates. Preferred materials for food packaging often consist of a first substrate, such as a film, which is generally thin and transparent (about 30 microns), and can be printable, and a second substrate which can be another type of material often is thinner film about 20 microns, a metal foil, a metallised film or a transparent film.
Mõnel juhul on leitud, et reaktiivsete polüuretaanliimide kasutamine põhjustab pakendatud toidu saastumist -reageerimata isotsüanaatide ja kantserogeensete aromaatsete amiinidega, mis tekivad liimikomponentide reageerimisel toidu niiskusega. Seegaliimi katmisraskused used in lamination will be not higher than 1.5-5g/m². food packaging materials may release migration compounds which result from the adhesives used in manufacturing such materails.
