Micro and nanocellulose extracted from energy crops as reinforcement agents in chitosan films

Abstract

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 micro (MCC) and nanosized crystalline particles (CNC) are suitable examples of bioproducts that provide applications in many distinctive areas. The insertion of these homogeneously scattered particles, as a reinforcement agent, into the chitosan (Ch) films, is seen as a promising possibility to surpass the shortcomings associated with bioplastics. Therefore, the aim of this work was to test a combination of MCC and CNC obtained from biomass from giant reed (Arundo donax L.), kenaf (Hibiscus cannabinus L.) and, miscanthus (Miscanthus × giganteus Greef et Deu.) as reinforcement agents in Ch films. Extraction of MCC and CNC was carried out via an alkaline pre-treatment approach followed by acid hydrolysis. The particles were incorporated in Ch at different rates (1.5 %, 2 %, and 2.5 % w/w of chitosan), and the resultant biocomposites were fully characterized in terms of their morphology, mechanical and optical properties, permeability (oxygen and water vapor), water wettability, thermal analysis, X-ray diffraction, and FT-IR. Chitosan films reinforced with commercial nanocellulose at the same rates were tested for comparison. It was observed an improvement for the majority of samples after the incorporation of MCC/CNC, as planned. The sample with MCC/CNC isolated from giant reed was the one that most improved the properties of the film. Between the amounts added, the 2.5 % level presented the most encouraging effects, by improving considerably the strength and stiffness and by reducing the oxygen and water vapor permeabilities, essential features in the use of bio-based films by e.g. the food packaging industry. For this MCC/CNC rate, the films demonstrated equivalent potential to the film with 2 % commercial CNC. Predominantly, the different analyses displayed in the study indicated that biomass from the three lignocellulosic crops tested may afford a viable alternative source of reinforcing agents to be applied in the biocomposites production.