Author: ITENE
The use of plastic materials due to their great variety of properties and structures, has caused the plastic packaging sector to represent around 44% of the plastics market[1]. However, these packaging systems, many of which involve the use of multilayer structures for high requirement applications, present issues to be classified and/or recycled (heterogeneity of waste, separation difficulties, degradation, contamination, etc.), with the potential loss of resources, as well as problems in the management of packaging waste. According to data from Plastics Europe, in 2020, plastic packaging waste achieved a total 17,9 MT, and only 46% was recycled, which is reduced to 32% using the new calculation methodology of the European Commission’s Packaging and Packaging Waste Directive. This current situation is still far from the targets set by the European Plastics Strategy, Directive (EU) 2018/852 on packaging and packaging waste, and the Waste and Contaminated Soil Law. Among these targets, it can be highlighted the tax on the use of virgin plastics, and to achieve by 2030 a plastic recycling rate of 55% and 100% of packaging reusable, recyclable or compostable.
These measures have recently led to a great deal of interest in the simplification and upcycling of packaging structures, to facilitate their recyclability and the use of bioplastics (biodegradable materials and/or materials from renewable sources), especially within the packaging sector. Much of that interest comes from biodegradable materials such as polylactic acid (PLA), polybutylene adipate terephthalate (PBAT) and polyhydroxyalkanoates (PHAs), and biobased materials such as biopolyethylene (bioPE) or biopolyamide (bioPA). The latter, despite promoting a reduction in the consumption of non-renewable natural resources, are not biodegradable/compostable. In this sense, it is crucial to design recyclable solutions.
This interest in bioplastics is reflected in the production capacity, which is expected to increase from 1,79 million tons in 2021 to approximately 6,29 million tons in 2027 according to European Bioplastics. However, this capacity is still far from that of petroleum-derived polymers, which reached 351 million tons in 2021. Besides these production capacities, applicability of bioplastics is hindered due to its cost and limited properties (mechanical, barrier, thermal, optical, etc.) and/or processability. Additionally, multilayer structures are normally necessary as one single material does not fulfill all requirements needed. In order to deal with all these problems and to be able to meet the circularity requirements set by the European Commission for the packaging sector, major research efforts are required.
An example of research on this topic is the Bionanopolys project, funded by the European Union’s Horizon 2020 Research and Innovation Programme, in which one of the main objectives is to develop bionanocomposites to achieve the properties of non-renewable/non-biodegradable products currently available in the packaging market. These bionanocomposites are divided into two main categories, recyclable biobased solutions, and biodegradable solutions.
These solutions present some advantages over conventional plastics normally used in multilayered structures since, due to its recyclability and/or biodegradability, and renewable origin, significantly reduces the environmental impact of these flexible packaging applications if properly designed and used. However, as mentioned before, limited performance of bioplastics restricts its market share and application fields. Thus, to improve the properties of these materials, different approaches are being developed within Bionanopolys project.
The first of them is the use of biobased nanoadditives such as cellulose nanofibers or cellulose nanocrystals, but also other nanoadditives like nanoclays. As main advantage from this concept is to use small amounts of additives to increase in a great manner the properties of the bioplastics and even reduce their thickness. In this way, recyclable and/or biodegradable multilayer solutions can be designed. However, to achieve a good performance of these nanoadditives within bioplastics, their interaction with the polymeric matrices needs to be improved. This can be done improving the interaction between matrix and additives by functionalizing the surface of such nanoadditives, but, to achieve a good dispersion of the nanoadditive, it is critical as well to design tailor-made screw configurations and select optimum processing parameters to maximize the dispersion of additives. However, if dispersion is not properly assessed, the design of screw configurations and optimization of processing parameters becomes very time-consuming. In the Bionanopolys project, in-line rheology and advanced simulation software for the compounding process are being developed to evaluate optimise the design and dispersion in a more efficient way.
Another approach to improve the properties of bioplastics, especially those biodegradables, is by mixing it with other types of biodegradable materials, creating a new material with different or improved properties that fulfil the requirements of the final application. The properties can vary widely choosing different components of the mixture (matrices/additives), and/or changing the proportions of each one of them, as well as its processing parameters. For this purpose, it is crucial the selection of the bioplastics and the design of specific screw configurations that allow an optimum blending without leading to potential material degradation. This approach has some limitations in terms of processing and compatibility between bioplastics, to obtain an homogeneous and well dispersed blend. To tackle this issue, reactive extrusion routes are being developed, whose can also be combined with the functionalized nanoadditives to boost its properties and reach the performance of the current non-renewable market solutions.
With these approaches, it is expected to improve the properties of a wide range of flexible packaging applications in a more sustainable way. These developed bionanocomposites will be tested in different pilot lines in WP5 for the production of bionanoproducts such as multilayer recyclable and biobased flexible packaging. One of them will consist of a multilayer recyclable solution based on bioPE with a thin layer of reinforced bioPA for vacuum packed applications. Another bioproduct will consist of upcycled biodegradable polymers reinforced with biobased additives to achieve a high barrier performance for vacuum packed applications as well with an extended shelf life.
[1] Plastics the Facts 2022 – Plastics Europe
