Hydrophobic Recovery of Plasma-Hydrophilized Polyethylene Terephthalate Polymers

Oxygen plasma is widely used for enhancing the wettability of numerous polymers, including polyethylene terephthalate (PET). The treatment with plasma containing oxygen will cause surface functionalization with polar functional groups, which will, in turn, improve the wettability. However, the exact mechanisms leading to the hydrophilic or even super-hydrophilic surface finish are still insufficiently explored. The wettability obtained by plasma treatment is not permanent, since the hydrophobic recovery is usually reported. The mechanisms of hydrophobic recovery are reviewed and explained. Methods for suppressing this effect are disclosed and explained. The recommended treatment which assures stable hydrophilicity of PET samples is the treatment with energetic ions and/or vacuum ultraviolet radiation (VUV). The influence of various plasma species on the formation of the highly hydrophilic surface finish and stability of adequate wettability of PET materials is discussed.

Biodegradable and Flexible Nanoporous Films for Design and Fabrication of Active Food Packaging Systems

Nanotechnology has facilitated the development of active food packaging systems with functions that could not be achieved by their traditional counterparts. Such smart and active systems can improve the shelf life of perishable products and overcome major bottlenecks associated with the fabrication of safe and environmentally friendly food packaging systems. Herein, we used a plasma-enabled surface modification strategy to fabricate biodegradable and flexible nanoporous polycaprolactone-based (FNP) films for food packaging systems. Their capacity for preserving tomatoes, tangerines, and bananas at room and refrigeration temperatures was tested by analyzing various fruit parameters (mold generation, appearance changes, freshness, weight loss, firmness, and total soluble solids contents). Compared with commonly used polyethylene terephthalate-based containers, the proposed system enhanced the fruit storage quality (i.e., retained appearance, reduced weight loss, better firmness, and sugar contents) by controlling moisture evaporation and inhibiting mold generation. Thus, the FNP film represents a new active food packaging strategy.

Thermal Stability and Crystallization Behavior of Contaminated Recycled Polypropylene for Food Contact

Polypropylene is one of the most widely used polymers, especially in the food packaging industry, which causes negative environmental effects. Recycling is a good option to partially solve this environmental problem. Thus, the polymer was contaminated with a cocktail to simulate the conditions of disposal and recycling following FDA guidelines. The influence of contaminants on recycled PP was analyzed by quiescent and nonquiescent crystallization. It was found that the contaminants alter the crystallization flow since longer induction times were observed for all contaminated samples. Also, the thermal behavior was performed considering that the thermogravimetric (TGA) results indicated an increase in the stability with the presence of contaminants. Therefore, a deep investigation using the induced oxidation time and induced oxidation temperature was performed. The contaminants play an important role in the crystallization process, as well as, in the degradation of the samples. Furthermore, the use of TGA and DSC as complementary techniques is fundamental to analyze this influence.

Barrier properties to surrogates of hydrogenated carbon nano-films deposited on PET by plasma-enhanced chemical vapour deposition

Poly(ethylene terephthalate) resin was contaminated with a series of surrogates using a US Food and Drug Administration protocol. The contaminated samples were coated with two different kinds of hydrogenated amorphous carbon thin films (a-C:H): one with diamond-like hydrogenated amorphous carbon and another with polymer-like hydrogenated carbon (PLCH) phases. To evaluate the barrier properties of the a-C:H films, migration assays were performed using food simulants. After the tests, analysis by gas chromatography with different detectors was carried out. The appearance of the films before and after the migration experiments was studied by field emission scanning electron microscopy. The results showed that a-C:H films have good barrier properties for most of the evaluated compounds, mainly when they are deposited as PLCH phase.