Improvement of Barrier Properties of Films

Developing high-barrier films has been the main challenge for film suppliers. Surface modification, crystallization and orientation, blending, and incorporation of nanoparticles as an impermeable phase have been suggested by researchers for the improvement of barrier properties. 

Typically, it is difficult to obtain all the desirable barrier properties from a single film layer. Polymer suppliers and the plastic film manufacturers have long recognized the need for multilayered, laminated, coextruded, coated, and metalized films to meet the varied requirements of food packaging. High-barrier packaging can comprise several different layers and various types of resins, which provide advanced properties for such things as extended shelf life and the ability to let in certain gases to change product coloring. 

Surface modification is one method for improving barrier properties. Transparent silicon oxide (SiOx) coating on polymers such as PET, PP, PA, polyethylene naphthalate (PEN), and polyvinyl alcohol (PVA) films have been greatly investigated by researchers. Many researchers are interested in surface modification through SiOx coating for food packaging, medical devices, and beverage packaging applications because of its transparency, water resistance, recyclability, retortability, microwave use, and excellent barrier properties. Two techniques have been used for SiOx coating: physical vapor deposition (PVD) and plasma-enhanced chemical vapor deposition (PECVD). PECVD was preferable because it can be used to deposit materials at low temperatures, with excellent coverage at a higher deposition rate, creating better adhesion and less brittle failure than films produced by PVD. From the industrial point of view, PVDC, well known as a high-barrier polymer, is coated on the surface of polymer films in order to improve the oxygen barrier property. the OTRs of a number of plastic films that are PA6/PVDC and PP/PVDC coated are compared. The data indicate orders of magnitude differences in the oxygen barrier properties of different plastic films compared to the films coated with PVDC. 

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