Cassava starch-based nanocomposites reinforced with cellulose nanofibers extracted from sisal Jamille Santos Santana, 1 Jamile Marques do Ros  ario, 2 C  ıcero Cardoso Pola, 3 Caio Gomide Otoni, 4 Nilda de F  atima Ferreira Soares, 3 Geany Peruch Camilloto, 2 Renato Souza Cruz 1,2 1 Department of Chemical Analyses, Faculty of Pharmacy, Graduate Program in Food Science, Federal University of Bahia (UFBA), Rua Bar~ ao de Jeremoabo, s/n, Salvador, BA 40170-110, Brazil 2 Department of Technology, Faculty of Food Engineering, Feira de Santana State University (UEFS), Av. Transnordestina, s/n, Feira de Santana, BA 44036-900, Brazil 3 Department of Food Technology, Laboratory of Food Packaging, Federal University of Vic ¸osa (UFV), Av. PH Rolfs, s/n, Vic ¸osa, MG 36570-900, Brazil 4 Department of Materials Engineering, Federal University of S~ ao Carlos (UFSCar), PPG-CEM, Rodovia Washington Lu  ıs, Km 235, S~ ao Carlos, SP 13566-905, Brazil Correspondence to: R. S. Cruz (E-mail: cruz.rs@uefs.br) ABSTRACT: Cellulose nanofibers were extracted from sisal and incorporated at different concentrations (0–5%) into cassava starch to produce nanocomposites. Films’ morphology, thickness, transparency, swelling degree in water, water vapor permeability (WVP) as well as thermal and mechanical properties were studied. Cellulose nanofiber addition affected neither thickness (56.637 6 2.939 mm) nor transparency (2.97 6 1.07 mm 21 ). WVP was reduced until a cellulose nanofiber content of 3.44%. Tensile force was increased up to a nanocellulose concentration of 3.25%. Elongation was decreased linearly upon cellulose nanofiber addition. Among all films, the greatest Young’s modulus was 2.2 GPa. Cellulose nanofibers were found to reduce the onset temperature of thermal degradation, although melting temperature and enthalpy were higher for the nanocomposites. Because cellulose nanofibers were able to improve key properties of the films, the results obtained here can pave the route for the development and large-scale production of novel bio- degradable packaging materials. V C 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44637. KEYWORDS: biopolymers and renewable polymers; cellulose and other wood products; composites; packaging; polysaccharides Received 17 July 2016; accepted 7 November 2016 DOI: 10.1002/app.44637 INTRODUCTION Nonrenewable synthetic materials play an important role in mod- ern society, but these are being increasingly associated with remark- able environmental problems as a result of the accumulation of non-biodegradable plastics. 1 Obtaining biodegradable materials exhibiting thermoplastic properties from renewable sources (e.g., starch and cellulose) denotes a means of reducing the environmen- tal impact caused by the intense use of petroleum-derived materi- als. 2–6 In this context, starch has been pointed out as a feasible alternative for plastics derived from fossil sources, 7–9 mainly because it is renewable, widely available in nature, and inexpensive. Starch comprises two polysaccharides derived from a-D-glucose: amylose and amylopectin. In its native form, starch features a granular structure, which may be transformed into a continuous phase, named thermoplastic starch (TPS). 10 This can be achieved through the input of thermal and/or mechanical energy together with the addition of a plasticizer, i.e., a sub- stance capable of modifying starch molecular network in a way that increases its free volume. 11 Plasticized starch still presents some limitations, including high affinity to water (and, thus, water absorption) as well as weak mechanical properties, the latter being strongly affected by relative humidity (RH). 12 Therefore, the addition of cellulose nanofibers stands out as a promising strategy to overcome this hurdle. 13,14 Cellulose nanofibers are crystalline domains featuring unique physical characteristics: stiffness, thickness, and length. 15 These highly oriented structures lead not only to more resistant mate- rials, but also to materials having distinct optical, magnetic, electrical, and conductivity properties if compared to the mac- roscopic material. 16 Nanofibers may be obtained from numerous lignocellulosic sources, including coconut husk, 17 cassava bagasse, 18 eucalyptus V C 2016 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM J. APPL. POLYM. SCI. 2017, DOI: 10.1002/APP.44637 44637 (1 of 9)