bioresources. com
PEER-REVIEWED REVIEW ARTICLE
PLA, PBS, and PHAs are commercial, biodegradable biopolymers, with characteristics that are comparable to conventional petroleum-based thermoplastics. The challenge in considering these polymers is their relatively high price, low production volumes, and the more challenging processability compared to that of conventional polymers, e.g. , polyolefins. In addition, the most common bio-based raw materials for PLA, PBS, and PHAs production compete with food. However, different waste-streams, wastewaters and agro-wastes, have been studied as an alternative feedstock. The PLA, PBS, and PHAs offer adequate mechanical and barrier properties for many applications, specially for packaging. Nevertheless, in order to enable a more extended use of these biopolymers in the packaging industry, the price level should be comparable to that of conventional polymers. This means the need for cheaper raw materials, more efficient production processes, thinner barrier layers, or the development of cost-efficient blends or composites. Another powerful accelerator could be a change in the legislation considering packaging materials, e.g. , similarly to European directive of single use plastics or French ordinance Décret n° 2016-1170 (2016). For both wood-based or microorganism-based biobarriers, the incorporation of inorganic and mineral nano- and microparticles offer interesting prospects, for example, to develop antibacterial, thermal resistance and other properties (Hoseinnejad et al. 2018; Wang et al. 2018). For instance, high-barrier and fully biodegradable food packaging materials have been achieved by coating PLA with glycol chitosan-clay nanocomposite (Habel et al. 2018). Likewise, major advances have been made with compositions to achieve UV protection (Niu et al. 2018) as well as scavenging and releasing activities, all relevant to food and pharmaceutical packaging, to extent the shelf life, for diagnostic, identification and communication (quality tracking, brand protection, etc .). This topic has been reviewed recently (Janjarasskul and Suppakul 2018) and is a subject of current research. In all these contexts, safety and regulatory aspects need careful attention. While this review did not discuss the topic in detail, an interesting solution to biodegradability, to improve the properties of packaging materials, and to enhance barrier effects, is the use of multicomponent polymers and blends. This includes the synthesis of systems via interpenetrating networks (Bai et al. 2015). For related purposes, various compatibilizers, including those that can be adopted during melt processing, have been discussed (Muthuraj et al. 2018). Along similar ideas, proteins have been proposed as compatibilizer and eco-friendly dispersant in composites comprising cellulose nanofibrils and PLA (Khakalo et al. 2018). Another aspect of interest is the possibility to make patterned biobarriers, which can be useful to engineer surfaces in advanced applications (Guo et al. , 2018). Finally, the so-called “solvent welding” is being researched to tune the surfaces of biobased films, expanding the scope of properties and offering a possibility to facilitate multilayered structures (Reyes et al. 2019) CONCLUSIONS Packaging materials are selected by end use requirements and they can be combined to fulfill given target properties. No single bio-based material will satisfy all potential markets or applications. Existing petroleum-based barrier solutions comprise products that have been developed over the course of several decades. The use of bio- based materials is not as matured and needs further development. Growing interest in designing packaging concepts include multilayer structures. PLA, PBS, and PHBs are
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Helanto et al. (2019). “ Bio-based barriers ,” B io R esources 14(2), Pg #s to be added.
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