Macromolecular Nanotechnology Tailoring the morphology and properties of waterborne polyurethanes by the procedure of cellulose nanocrystal incorporation Patrícia Santiago de Oliveira Patricio a,⇑ , Iaci Miranda Pereira b , Natália Cristina Ferreira da Silva a , Eliane Ayres c , Fabiano Vargas Pereira d , Rodrigo Lambert Oréfice e a Centro Federal de Educação Tecnológica de Minas Gerais, Av. Amazonas, 5253, Belo Horizonte, MG CEP 30421-169, Brazil b Centro de pesquisa do Exercito, Rio de Janeiro, RJ, Brazil c Universidade do Estado de Minas Gerais, Av. Antônio Carlos, 7545, Pampulha, Belo Horizonte, MG CEP 31270-010, Brazil d Departamento de Química, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, Pampulha, Belo Horizonte, MG CEP 31270-901, Brazil e Departamento de Engenharia Metalúrgica e de Materiais, Universidade de Federal de Minas Gerais, Av. Antônio Carlos, 6627, Pampulha, Belo Horizonte, MG CEP 31270-901, Brazil article info Article history: Received 23 January 2013 Received in revised form 25 July 2013 Accepted 4 August 2013 Available online 19 August 2013 Keywords: Polyurethane waterborne Cellulose nanocrystals Small angle X-ray scattering Mechanical properties abstract Polyurethane waterborne synthesis was performed using a two-step method, commonly referred to as a prepolymer method. Nanocomposites based on waterborne polyurethane and cellulose nanocrystals were prepared by the prepolymer method by altering the mode and step in which the nanofillers were incorporated during the polyurethane formation. The morphology, structural, thermal, and mechanical properties of the resulting nanocom- posite films were evaluated by Fourier transform infrared spectroscopy (FTIR), small angle X-ray scattering (SAXS), scanning electron microscopy (SEM), and tensile tests. FTIR results indicated that the degree of interaction between the nanofillers and the WPU through hydrogen bonds could be controlled by the method of cellulose nanocrystal incorporation. Data obtained from SAXS experiments showed that the cellulose nanocrystals as well as the step of the reaction in which they are added influenced the morphology of the polyure- thane. The reinforcing effect of CNCs on the nanocomposites depends on their morphology. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Polyurethanes derived from aqueous dispersions, namely waterborne polyurethanes (WPUs), have replaced conventional polyurethanes based on volatile organic com- pounds (VOCs) in several applications, such as adhesives [1], membranes [2], food packaging [3] and biomedical de- vices [4]. The advantages of WPU have been reported by several authors and are mainly related to reduced safety risks and environmental concerns [5]. The major thrust of research and development has been on replacing VOCs with water during the synthesis of the polyurethanes while retaining the same high properties as when VOCs are used. Furthermore, these WPUs could have higher rates of biodegradation compared to conventional polyure- thanes [6]. WPUs are usually prepared with aliphatic diis- ocyanates because the reactivity of aromatic isocyanates with water is so high that it is difficult to prepare WPU with them [7]. Aliphatic diisocyanates are usually consid- ered less toxic than 4,4-diphenyl-methane diisocyanate (MDI), which is commonly used in conventional polyurethanes. The interest in segmented polyurethanes is also related to their molecular architecture consisting of incompatible 0014-3057/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.eurpolymj.2013.08.006 ⇑ Corresponding author. E-mail addresses: patriciapatricio@des.cefetmg.br, patriciasop@yahoo. com.br (P.S. de Oliveira Patricio). European Polymer Journal 49 (2013) 3761–3769 Contents lists available at ScienceDirect European Polymer Journal journal homepage: www.elsevier.com/locate/europolj MACROMOLECULAR NANOTECHNOLOGY