All-natural polymer composites with engineered properties

In the last decades, petroleum-based synthetic polymers have been widely used for the production of plastic materials thanks to their versatile and multifunctional properties. Nevertheless, the environmental problems related to their total inability to biodegrade and the release of toxic chemical with time are pushing researchers to exploit natural polymers from bioresources as building blocks to fabricate plastic-like materials. Methods for the extraction of natural polymers from plants, animals, and microorganism have already been proposed in literature, but these natural compounds still present weaknesses related to their mechanical and optical properties, humidity resistance, and barrier properties. The aim of this Thesis is the design and the development of all-natural polymer composites combining the properties of various natural polymers both as matrix and as nano-micro fillers in just one combined material. A detailed analysis about the proper modification of the initial structure will be given, with emphasis on the tuning of the final properties. The production methods used in this work are compatible with processes, such as casting, extrusion, and hot-pressing, used in plastics processing industry in order to develop natural composite materials that can be easily scalable. Moreover, a comprehensive comparison of these novel natural composites with respect to commonly used synthetic materials is shown. After a general introduction about the economy and the main advantages and drawbacks of petroleum-based plastics, a meticulous review of the main biopolymers used as sustainable alternatives to their synthetic counterparts and a description of the main advantages of natural polymeric composites is discussed. Other additional Chapters form this Thesis: 1. The first one is about the functionalization of cellulose acetate with oleic acid. 2. The second one is focused on the amorphous reassembly of the three main components of wood, i.e. cellulose, hemicellulose and lignin. 3. The third one presents the fabrication of biocomposites from aleuritic acid and nanocellulose. 4. The fourth one is related with the reinforcement of fibrous composite mycelium with a polyaleuritate coating. 5. The fifth one describes the fabrication of plant cuticle-like packaging films from tomato pomace agro-waste, beeswax, and sodium alginate.