Sustainable and advanced barrier coating solutions for paper packaging

 
The escalating global crisis of plastic waste calls for an urgent exploration of sustainable packaging alternatives. Petroleum-based plastics are prevalent in food packaging due to its barrier properties. However, they have a non-biodegradable nature, and contribute largely to microplastics accumulation in the environment. Developing biodegradable materials that effectively protect and preserve food while minimizing environmental impact is mandatory in current times. This study focuses on enhancing paper's barrier properties using different coating solutions as a promising approach to address this critical challenge. Different coatings technologies (PVD, Spray-coating, Screen-printing, Knife-coating, Layer-by-layer, Extrusion Coating and others) were used to produce monolayer and multilayer solutions to improve the barrier to oil, water vapour and oxygen. The performance of different solutions was evaluated in grease resistance test, in Water Vapour Transmission Rate (WVTR) and Oxygen Transmission Rate (OTR). Promising results were obtained by monolayer coating through wet coating techniques. A biodegradable, food-safe biopolymer coating, with less than 10 µm of thickness, achieved maximum performance in the grease resistance. Multilayer coatings showcased superior overall performance. Hybrid multilayers, combining multiple coating technologies, represented a significant innovation. These systems allowed for the integration of diverse functionalities to enhance overall product performance. Two examples of this hybrid approach: a combination of a biopolymer blend and a thin ceramic layer provided an OTR of 25 cc/(m2·24h) (23 °C and 50% RH), a great improvement compared to the control since the paper substrate's OTR value was impossible to measure due to "sensor overload" of the permeability equipment; moreover, this solution presented an exceptional grease resistance; other promising solution is a multilayer of biodegradable, food-safe biopolymer coating combined with a Layer-by-layer system, achieved an outstanding WVTR reduction of 89% (38 °C and 90% RH) in comparison to the paper substrate and kept the grease resistance in the highest level.