“…To obtain them, nanoparticles of various substances are introduced into the polymer matrix, and the resulting polymer composites may have, among other features, better mechanical properties, lower gas permeability, and increased microbiological resistance [ 5 ]. In some cases, introducing fillers into the polymer matrix also has economic reasons [ 6 ]. A variety of products are used to produce polymer composites, including biopolymers, such as lignin [ 1 , 7 , 8 , 9 , 10 , 11 , 12 ] and cellulose [ 13 , 14 , 15 , 16 , 17 , 18 , 19 ]; inorganic substances, e.g., titanium dioxide [ 20 , 21 , 22 , 23 ]; and hybrid materials, e.g., MgO/lignin [ 24 ] or TiO 2 /lignin [ 25 ].…”