3596
Cellulose (2018) 25:3595–3607
Graphical Abstract
Keywords Paper coating Regenerated cellulose N -Methylmorpholine N -oxide NMMO Cellulosic coating Mechanical properties Surface modification
material properties, while at the same time developing novel composite or hybrid biomaterials (Salas et al. 2014; Hubbe et al. 2017). Different forms of cellulose, in particular, microfibrillated, microcrystalline cellu- lose and nanocellulose, are currently among the substances widely studied to meet these objectives (Lavoine et al. 2014; Nakagaito and Yano 2005). Numerous scientific publications (Zimmermann et al. 2005, 2010; Henriksson et al. 2008; Hansen and Plackett 2008; Fukuzumi et al. 2009; Tingaut et al. 2011; Lavoine et al. 2012; Dufresne 2012, 2013; Siro´ and Plackett 2010; Savadekar et al. 2015; Spence et al. 2010; Kangas et al. 2014; Mngomezulu and John 2017) indicate the possible application of these forms of cellulose in the production of new, environmentally friendly materials. Those researchers determined, among other things, that the addition of micro- and nanocellulose significantly influenced the material structure. Therefore, it is possible to modify the mechanical and barrier properties of fibrous materials. For example, Ferrer et al. (2012) and Fall et al. (2014) reported that nanocellulose-based materials had the following major features: high specific surface area, high density (1100–1560 kg/m 3 ) and high strain at break (up to 10%). Additionally, the elastic modulus of cellulose nanocrystals could be as high as 143 GPa (Sˇ turcova´ et al. 2005). From a practical viewpoint, the hydrophilicity of microcrystalline cellulose and nanocellulose is a significant advantage, as it enables them to be applied in water-based systems and/or in mixtures with other hydrophilic substances. The presence of the –OH groups in the cellulose macro- molecule may contribute to the ordered structures of the cellulose chains. As a result, these structures possess hydrogen bonding potential and, thus, they may be combined with other polymer materials (Gardner et al. 2008; Erdman et al. 2016). This makes
Introduction
The coating of paper materials is one of the most commonly applied methods for altering their surface properties. Depending on the coating suspension composition, it is possible to improve paper strength, adhesive, printing, barrier and antibacterial properties, control the coefficient of friction and fire retardancy, modify thermal and electrical conductivity, and also to enhance the many different properties of other end- products (Choi et al. 2002; Tracton 2007; Andersson 2008; Gardner et al. 2008; Liu et al. 2011; Salas et al. 2014; Mngomezulu and John 2017). A lot of sub- stances used for coating purposes are of synthetic origin (e.g. PET, PVC, PP, waxes, latexes). Such compounds—apart from their advantages, i.e. good barrier properties, high strength, low price, easy application—have many drawbacks, especially with regard to their negative environmental impact and recycling difficulties (Andersson 2008). This is one of the reasons for research aiming at reducing the content of synthetic polymers or replacing them by natural polymers (Khwaldia et al. 2010). Nowadays, such reports and their results can be found in the literature discussing the possible application of more environ- mentally friendly biopolymers, such as whey proteins, chitosan (Ga¨llstedt et al. 2005), starch (Garcia et al. 1999) and alginates (Rhim et al. 2006). Another, but equally important, reason to conduct such research is to seek out truly environmentally friendly substances, which would make it possible to obtain new paper
123
Made with FlippingBook Digital Publishing Software