Cellulose NANOFIBER-polyethylene nanocomposites modified by polyvinyl alcohol Alper Kiziltas, 1,2 Behzad Nazari, 3 Esra Erbas Kiziltas, 1,4 Douglas J. S. Gardner, 1,4 Yousoo Han, 1 Todd S. Rushing 5 1 Advanced Structures and Composites Center (AEWC), University of Maine, Orono, Maine 04469 2 Department of Forest Industry Engineering, Faculty of Forestry, University of Bartin, Bartin, 74100, Turkey 3 Department of Chemical Engineering, University of Maine, Orono, Maine 04469 4 The Scientific and Technological Research Council of Turkey (TUB _ ITAK), Tunus Cad, Kavaklıdere, Ankara 06100, Turkey 5 U.S. Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg Mississippi 39180 Correspondence to: A. Kiziltas (E - mail: kiziltasalper@gmail.com) ABSTRACT: The uniform dispersion of cellulose nanofibers (CNFs) in non-polar polymer matrices is a primary problem to over- come in creating novel nanocomposites from these materials. The aim of this study was to produce CNF-polyethylene (PE) nano- composites by melt compounding followed by injection molding to investigate the possibility of using polyvinyl alcohol (PVA) to improve the dispersion of CNF in the PE matrix. The tensile strength of CNF- filled composites was 17.4 MPa with the addition of 5 wt % CNF–PVA, which was 25% higher than the strength of neat PE. The tensile modulus of elasticity increased by 40% with 5% CNF–PVA addition. Flexural properties also significantly increased with increased CNF loading. Shear viscosity increased with increasing CNF content. The elastic moduli of the PE/CNF composites from rheological measurements were greater than those of the neat PE matrix because of the intrinsic rigidity of CNF. Melt creep compliance decreased by about 13% and 45% for the com- posites with 5 wt % CNF and 10 wt % CNF, respectively. It is expected that the PVA carrier system can contribute to the develop- ment of a process methodology to effectively disperse CNFs containing water in a polymer matrix. V C 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42933. KEYWORDS: cellulose and other wood products; manufacturing; rheology; thermogravimetric analysis; thermoplastics Received 24 May 2015; accepted 15 September 2015 DOI: 10.1002/app.42933 INTRODUCTION Cellulose nanofibers (CNFs) have great potential as reinforce- ment in polymer nanocomposites because of their superior mechanical properties, nanoscopic size, abundance, low weight, renewability, biodegradability, nontoxicity, and biocompatibil- ity. 1–3 Therefore, CNFs have been extensively researched around the world, and the number of publications including research papers and patents on the preparation of nanocomposites con- taining CNFs has increased in recent years. 4–8 A broad range of potential applications of CNF to high-performance bio/nano- composites have been developed, and these applications are expected to open up opportunities for the replacement of con- ventional petroleum-based composites with new and improved materials. 1,2,9 However, despite the attractive properties of CNFs, there are several obstacles to their use including lack of cost-effective production methods, difficulty of dispersion in non-polar matrix systems and non-aqueous media, and inad- equate interfacial adhesion properties. 2,3 The degree of dispersion of CNFs in a thermoplastic matrix strongly depends on the conditions of the melt compounding and processing techniques, such as extrusion or injection mold- ing, used to prepare the CNF-reinforced polymer composites. 1,10 CNF dispersion in a thermoplastic can be limited by the proc- essing temperature, which is restricted to about 2008C with CNFs, and the incompatibility between hydrophilic CNFs and hydrophobic thermoplastics. 2,10–12 There are many publications based on cellulose nanocomposites; however, there have been relatively few reports on studies using CNFs with hydrophobic thermoplastics such as polypropylene (PP), polyethylene (PE), and polystyrene (PS). CNF reinforcement of hydrophobic ther- moplastic polymers has received far less attention than water soluble polymers or latexes as matrix resins for CNFs. Some reported examples of polyolefin (PP and PE)-based nanocom- posites reinforced with CNFs are summarized in Table I. Melt compounding was chosen over solvent casting for this study because melt processing is more practical for scaling up V C 2015 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM J. APPL. POLYM. SCI. 2016, DOI: 10.1002/APP.42933 42933 (1 of 8)