Development of functional coatings for different applications: from food packaging to fashion industry

Coatings are important in our society due to their contribution in terms of safety, health, comfort and well-being, for example, by offering protection from external agents to buildings, infrastructures, transports, food, and textiles. Since in our life most of the time we are in direct contact with them, for example in the shoes that we wear or in the food that we eat, it is essential that the materials used to develop the coatings are not toxic for our health. In addition, nowadays, the coating research-field and industry are looking for solutions to improve the sustainability of materials (e.g. biosourced, biodegradable, renewable materials) and processes (e.g. energy efficient manufacturing) in order to reduce their impact on the environment [1]. In this contest, the main objective of this work is to select sustainable materials in order to develop functional coatings for different applications, such as food packaging and leather industry. Concerning the food packaging, one of the main trend is to develop antimicrobial active coatings to reduce or avoid the bacterial growth on food, preserving its quality for a longer a time [2]. For this reason, a food grade sustainable copolymer and an antioxidant molecule, curcumin, have been combined to develop a sustainable and active coating for various substrates such as glass and polysaccharide films with the aim of proposing a coating for food packaging [3]. Due to the application, the coating presents appealing properties, such as reduction of gas exchange between the inside and the outside of the packaging, as well as transparency to allow the visibility of the food, and UV-filtering ability to protect the food from the UV light. Last but not least, the coating is characterized by low bacterial adhesion, making it a possible candidate for active food packaging. Since the challenge of finding sustainable and green solutions for low environmental impact coatings has been evolving from avoiding petroleum-derivatives into the opportunity to get materials derived from renewable resources and waste [4], in this work, as next step, by-products of the food industry have been taken in consideration to develop a hydrophobic and water resistant coating for fish leather. Since salmon fish skin is one of the main waste of the aquaculture, the Horizon 2020 project, FISHSKIN [5], has considered it a sustainable raw material for fashion transforming it into leather. In this contest, the coating for fish leather has been developed by using the epoxidized soybean oil, which derives from the soybean oil produced in excess in many geographical areas respect to the consumption in cooking [6], and a sustainable trimer acid. As a result, it improved the waterproof ability of the leather in terms of water and humidity without affecting itsbreathability and softness. Both the developed coatings could be easily scalable in an industrial process and considered as possible solutions in their fields of application, firstly because they respect the sustainability goal as main aim of the industries. In addition, the curcumin-based coating could be easily applied on different substrates, such as paper, PET and other food packaging materials, as well as the ESO-based coating could make water resistant cotton, as demonstrated, or other functional materials, such as paper, used also in other fields of application.