Superficial modification in recycled PET by plasma etching for food packaging

Abstract

An oxygen plasma treatment has been used to improve the adhesion of amorphous hydrogenated carbon (a-C:H) films onto surfaces of recycled poly(ethylene terephthalate) (PET). Modifications produced by the oxygen plasma on the PET surface in chemical bonds and morphology were investigated by X-ray photoelectron spectroscopy and atomic force microscopy, respectively. Contact angle measurements were used to study the changes in the surface wettability. Adhesion of the a-C:H film onto the PET surface was investigated by the tape test method. It was observed that the improvement in film adhesion is in good correlation with the increase in surface roughness, due to plasma etching, and with the appearance of oxygen-related functional groups at the surface. The results of this study indicate that a-C:H-coated recycled PET can be used in food packaging. The a-C:H film could be used as a functional barrier to reduce or prevent migration of contaminants from the polymer to the package content.

The Effects of Accelerated Aging and Contact with Food Simulants on the Adhesion of Amorphous Hydrogenated Carbon Films Deposited on Clarified Polypropylene

“…The adhesion results were contrary to previous observations that used a polar polymer (PET) as the substrate [2,5]. In those studies, pre-treating the recycled PET substrate for 2.5 minutes with oxygen plasma provided good adhesion between the substrate and the a-C:H coating layer, both before and after the accelerated aging test.…”

“…Previous studies demonstrated that these films effectively reduce the migration of possible contaminants from recycled polymer without altering the food's organoleptic properties [1,2]. The efficiency of the functional polymer barriers for food packaging is evaluated by measurements of permeability that are directly related to its adhesion to the substrate [3][4][5]. Most studies in the literature have focused on poly(ethylene terephthalate) (PET) packaging [2,[5][6][7].…”

“…Fortunately, film adhesion can be improved by pretreating the substrate [3][4][5]9,11,13]. Examples of surface modifications related to polymers are plasma etching and the addition of new functional groups, such as those verified by Cruz et al [5] and Aguiar et al [9].…”

“…The efficiency of the functional polymer barriers for food packaging is evaluated by measurements of permeability that are directly related to its adhesion to the substrate [3][4][5]. Most studies in the literature have focused on poly(ethylene terephthalate) (PET) packaging [2,[5][6][7]. However, almost no studies in the literature evaluate these barriers' effectiveness in polyolefins considering their practical shelf life [2].…”

“…Fortunately, film adhesion can be improved by pretreating the substrate [3][4][5]9,11,13]. Examples of surface modifications related to polymers are plasma etching and the addition of new functional groups, such as those verified by Cruz et al [5] and Aguiar et al [9]. The effects of time, temperature, and liquid food simulants on the adhesion characteristics of a thermoplastic polymer coated with a-C:H-type PLC or DLC films were observed in one study only by Cruz et al [2], in PET.…”