Editor: Dr. Heli Kangas, VTT Technical Research Centre of Finland Ltd.
Bio-based nanomaterials
Everything you need to know about the new properties and opportunities with nanosized fibres
Current global trends towards the replacement of fossil-based materials and circularity of materials favour innovations in the sustainable natural fibre value chain. One such development is bio-based micro-and nanomaterials, which were originally invented decades ago but only became feasible to produce and use with technological breakthroughs made in the beginning of the 21st century.
Nanomaterials are materials having dimensions in the nanometer scale, usually between one to 100 nm and bio-based nanomaterials are nanomaterials originating from natural, plant-based materials. Cellulose nanomaterials, or nanocellulose, are perhaps the most widely known bio-based nanomaterials, but nanolignin and nano-sized hemicelluloses have also gained more interest recently. Bio-based nanomaterials exhibit special, nano-specific properties compared to their bulk materials, such as high specific surface area leading to increased reactivity or high aspect ratio providing them with strength and stiffness. The potential applications of bio-based nanomaterials range from more established ones, such as strength additive in paper and board, to very innovative ones, such as optical and electronic structures.
In the following chapters, the reader is introduced to different types of cellulose micro- and nanomaterials: cellulose nanofibrils (CNF), microfibrillated cellulose (MFC), cellulose nanocrystals (CNC), bacterial cellulose (BC) and microcrystalline cellulose (MCC) as well as to nanolignin. The main properties of these grades are discussed and the link between the properties and the potential applications highlighted. The most suitable characterisation methods for cellulose nanomaterials are also reviewed.
The unique properties of cellulose nanomaterials give them potential for numerous applications. Various applications are presented, of which the more advanced or potential ones – paper and board, packaging, composites, membranes and biomedical applications – are discussed in more detail. The market for cellulose nanomaterial containing products is introduced via patent landscape analysis and the commercial applications currently on the market presented based on the information given by the industry.
The production of cellulose nanomaterials is based on many different technologies, consisting of a combination of mechanical, enzymatic and chemical methods. Each of these categories is discussed and considerations on industrial production are also given. In addition, the status of current industrial production of cellulose nanomaterials is summarised. A novel post-processing method for bio-based materials, additive manufacturing (3D printing), is also introduced.
The unique properties of cellulose nanomaterials also make them behave differently towards their biological surroundings compared to the same materials with larger dimensions. This might have an effect on their safety, as this depends on many, still poorly understood factors, such as their physico-chemical properties, the size and shape of the particles, their aggregation properties, reactivity and specific surface properties among others. In addition, their exposure route, whether it is via respiratory route, gastronomic track, skin or eye, has an influence on their interactions. The literature published so far on the safety of cellulose nanomaterials is reviewed and the most important findings related to human health and occupational exposure as well as to environmental health and exposure are summarised.