Multilayer Barrier Paperboard Based on Nanocellulose and Biodegradable Thermoplastics, 2021 TAPPICon Live (21TAPL)

Nanocellulose is a cellulose-based natural polymer derived from plants, algae, or bacteria, with nano-scale dimensions, and has been the most researched biomaterial in recent times (Hubbe et al. 2017a). Nanocellulose is a broader term which includes various sub-types: cellulose nanocrystals (CNCs), cellulose nano/micro fibrils (CNFs/MFC) and bacterial cellulose (BC); and depending on the source and production process, the diameters and lengths vary in between 5 - 100 nm and 100 nm - >1 µm, respectively (Abitbol et al. 2016). Micro-fibrillated cellulose (MFC) lies on the coarser side of the nanocellulose spectrum and is produced by mechanical defibrillation of chemical pulp. By far, this is the least energy/chemical intensive process to produce nanocellulose at high enough production rates for it to be industrially relevant. Cellulose nanofibrils (CNFs) on the other hand have much finer dimensions, superior properties than MFCs, and are produced by chemical pre-treatment (TEMPO-oxidation, carboxymethylation, enzymatic hydrolysis) followed by mechanical defibrillation of cellulose pulp (Hubbe et al. 2017b). MFC/CNF-based films and coatings exhibit excellent barrier against oxygen, grease, and mineral oils (Aulin et al. 2010, Lavoine et al. 2012). Moreover, nanocellulose consists just of pure cellulose molecule with little to no chemical modifications, which makes it 100% biodegradable (Vilarinho et al. 2018). Therefore, MFC/CNF-based coatings, in recent years have been gaining interest as a promising biomaterial to replace non-biodegradable fossil-fuel based plastics and metallic aluminum in barrier food-packaging applications (Hubbe et al. 2017). 

Despite their immense potential as barrier packaging films and coatings, there are still a few challenges that nanocellulose faces before it can be commercialized. Traditionally, MFC/CNF-based films and coatings are prepared by laboratory scale batch processes such as, solvent casting, filtration, and drawdown coating, often followed by slow drying at ambient conditions. Nanocellulose suspensions in general, exhibit high viscosity and yield stress at low solids content of just 3%, have poor adhesion to various substrates and require additional drying infrastructure to process them on a large scale (Kumar 2018a). In addition, MFC/CNF films and coatings are extremely sensitive to moisture, with most of the barrier properties degrading, if not disappearing completely when the relative humidity approaches 90% (Spence et al. 2011). Polylactic acid (PLA), polybutylene adipate terephthalate (PBAT) and polybutylene succinate (PBS) are biodegradable thermoplastic polymers that have reasonably high tolerance against water vapor but poor barrier against oxygen  (Wu et al. 2021). In addition, these thermoplastic polymers can be processed into coatings by extrusion coating, which is a well-established process used by the packaging industry to traditionally coat low density polyethylene (LDPE) onto paper substrates.  

TAPPI conference proceedings and presentations, technical papers, and publication articles provide technical and management data and solutions on topics covering the Pulp, Paper, Tissue, Corrugated Packaging, Flexible Packaging, Nanotechnology and Converting Industries.

Simply select the quantity, add to your cart and your conference paper, presentation or article will be available for immediate download.