NANOCELLULOSE PRODUCED FROM LIGNOCELLULOSIC CROPS AS AMELIORATING AGENTS IN BIOBASED FILMS FOR THE PACKAGING INDUSTRY

The quest for more renewable and biodegradable materials currently represents a scientific key focus to combat the massive maneuver of non-sustainable products. Lignocellulosic feedstocks are rich in cellulose, hemicellulose, and lignin which, when recovered and separated, can give rise to innovative value-added products. Cellulose at the nanosized crystalline particles (CNC) are suitable examples of bioproducts that provide applications in many distinctive areas. The insertion of these homogeneously scattered particles, as an ameliorating agent, into bio-based polymers, is seen as a promising possibility to surpass the shortcomings associated with bioplastics. Therefore, the aim of this work was to identify a promising/potential biomass-to-product pathway, sustainable and innovative, for the bio-based industries, e.g. for the food packaging industry.
The extraction of nanocellulose (NC) from different lignocellulosic biomasses (giant reed, miscanthus, kenaf, sorghum, sunn hemp, hemp, coconut shell) was screened for an optimized procedure and its application as an ameliorating agent in bio-based films (chitosan) for the packaging industry was evaluated. The nanocellulose was obtained via alkaline pretreatments with NaOH, followed by a bleaching and acid hydrolysis. In the alkali pre-treatment process optimization, and taking into consideration a scale up of the process, preliminary results show that the time of 2 h 30 min and temperature of 60ºC can be chosen as optimum.
An optimum rate of NC incorporation in the bio-based films was also assessed based on the fully characterization of the resultant bionanocomposites (morphology, mechanical and optical properties, oxygen and water vapor permeability, water wettability, thermal analysis, X-ray diffraction, and FT-IR). Among the quantities incorporated, the 2.5% level presented the most encouraging effects, by improving considerably the strength (from 34 MPa to 38-48 MPa) and stiffness (increment in the range of 15-20%) and by reducing the oxygen and water vapor permeabilities (by 15-25%), essential features in the use of bio-based films by e.g. the food packaging industry. Also, it was the best level considering the ability to disperse de NC. Further, bionanocomposites are slightly more saturated and showed greater ultraviolet light block than the pristine bio-based films. Predominantly, the different results displayed in the study indicated that biomass from the different lignocellulosic biomass tested may afford a viable alternative source of ameliorating agents to be applied in the biocomposites production, thus contributing to meet the targets preconized by the sustainable development goals of the United Nations.