TiO2/nanocellulose hybrids as functional additives for advanced polypropylene nanocomposites

Abstract

Polymer composite materials with renewable fillers offering multiple functions, including good mechanical, photocatalytic and antibacterial properties, increased temperature and UV resistance, and enhanced gas barrier properties, are urgently needed in packaging production. The present research concerns a simple and inexpensive mechanochemical fabrication of TiO2/nanocellulose hybrids, where nanocellulose was obtained by enzymatic reactions. The effect of the weight ratio of components (TiO2 and nanocellulose) on the physicochemical and functional properties of the final products was examined. The obtained TiO2/nanocellulose hybrids were tested to determine dispersion, morphological and thermal properties. Composites of polypropylene with TiO2/nanocellulose hybrids were produced by a two-stage extrusion process. These composite materials, not previously reported in the literature, were subjected to detailed structural research using the X-ray diffraction method, analysis of phase transition using differential scanning calorimetry, analysis of nucleation and crystallization processes, as well as testing of mechanical properties. The composites with hybrid fillers produced very high values of tensile strength (approx. 55 MPa) and higher values of Young’s modulus (approx. 1700–1800 MPa). Moreover, these unique composites with TiO2/nanocellulose fillers also exhibited very good nucleating properties, including an increase in the crystallization temperature by 5–8 °C, a reduction of half-times of crystallization by approx. 40%, and high nucleation activity and thermal resistance. It was proven that all of the listed important properties of the composite materials strictly depend on the polymorphic structure, chemical composition, and dispersion and morphological properties of TiO2/nanocellulose hybrid fillers. In this work we describe for the first time a method of obtaining innovative polymer composites with TiO2/nanocellulose hybrid fillers, exhibiting properties that indicate a huge potential for application in many industries.