Polymer composites with cellulosic fillers: a study on gas transport properties

Given the growing awareness of environmental issues related to the use of traditional plastics, scientific research in recent years has focused on the study of new sustainable materials able to compete with petroleum-based polymers. Petrochemicals are widely used by the packaging industry, which is one of the main responsible for plastics production in Europe. ComBIOsites project, in the frame of the MSCA programme of the EU, aims at developing recyclable composite materials for packaging application. As part of this project, the present work deals with the study of the barrier properties of a biobased polymer reinforced with cellulosic fillers. Due to its abundance in several natural sources, cellulose is a promising candidate for producing new biobased polymers. A literature survey has been conducted to evaluate the actual potential of these materials in packaging application. The gas transport through polymeric materials has been treated using the permeation model and the main permeability tests adopted in the experimental investigations have been described. The insertion of nanofillers in the aim of reducing the permeability of polymeric systems has been studied. At the end of this research part, a review of the barrier properties of the main cellulosic nanomaterials, i.e. nanopapers and cellulosic nanocomposites, is reported. A particular reference is made to permeability data towards oxygen and water vapor, two of the main gases on which investigation on packaging materials are conducted. The experimental part of this work is focused on the characterization of a new composite material. Microfibrillated cellulose (MFC) has been used as reinforcement of a latex produced from a derivative of eugenol. Eugenol is a natural phenol that can be extracted from several plant resources. In compliance with sustainability criteria, this biobased latex has been obtained through an environmentally friendly process, i.e. aqueous emulsion polymerization. To assess the feasibility of using this material in the packaging field, permeability tests have been conducted. A Multiperm permeometer has been used to measure the Oxygen Transmission Rate (OTR) of nanocomposites in film form at desired condition of temperature and relative humidity. To evaluate the effect of fillers in determining the OTR, different MFC contents have been investigated. Part of the samples was also subjected to UV curing with the aim of improving its barrier properties. All the experimental data have been analyzed with the time-lag method for the estimation of the gas diffusion coefficient.