Desarrollo y optimización de nuevos materiales poliméricos, mezclas y compuestos de alto rendimiento medioambiental a partir de poliésteres y poliamidas procedentes de recursos renovables de interés en el sector envase y embalaje

Resumen

The main objective of this doctoral thesis has been focused on obtaining, developing and characterizing new formulations with high environmental performance from the use of polyesters and polyamides of renewable origin for the packaging sector. Throughout the research process, different improvement fronts have been addressed and evaluated with the aim of improving the properties of these materials to the maximum from a highly efficient point of view for the environment. For this purpose, different types of binary and ternary mixtures have been analysed, as well as the incorporation of natural fillers and reinforcements, the incorporation of additives and the use of plasticisers capable of solving problems of fragility and adhesion linked to certain polyesters such as PLA. In the first phase of the thesis, the miscibility and mechanical, thermal and morphological properties of ternary and binary mixtures based on polyester such as PHBH or PLA as main elements have been analysed and studied. Reactive extrusion (REX) has been used, obtaining very positive results with the incorporation of materials such as PCL, TPS and PBAT to the previously mentioned polyesters. Miscibility between the different components has been improved, using elements such as ESAO or compatibilizing agents such as PE-g-MA, PE-co-GMA and DCP, and above all, MLO as a natural compatibilizer, to develop totally renewable plastics with improved ductility and tenacity for application in the packaging sector. Within binary mixtures, the combination of PLA with a polyethylene of renewable origin has proved to be a promising solution within the packaging sector. On the other hand, to improve the toughness problems and the cost of PLA, the incorporation of additives and natural fillers has been evaluated and analysed. The use of natural oils derived from soya, flax and hemp has greatly improved the ductility of PLA. In addition, these oils have been combined with fillers derived from almond shells and orange peel in proportions of up to 30%, achieving a good balance of mechanical properties and obtaining WPCs capable of being highly efficient and cost-effective in some packaging applications. In the search for environmentally friendly polymers, the properties of different bio-based polyamides have been evaluated, and PA1010 has been selected as a perfect candidate thanks to its excellent properties and 100% renewable origin. In this context, the viability of incorporating natural fibres as reinforcement has been studied, with very promising results for slate fibres, achieving maximum resistance improvements of more than double with totally natural elements. It should be noted that the combination of PA1010 and PLA with different natural agents such as ELO and MLO for the manufacture of films, have resulted in a significant improvement in mechanical properties, and above all, an improvement in the oxygen barrier effect. In the last phase of the thesis, the extraction of antioxidant elements such as gallic acid from food waste has been optimized. The incorporation of this element in PLA has resulted in the manufacture of films for active packaging, greatly favoring its application in the food packaging sector. In addition, the effect of this type of natural antioxidant on the preservation of bio-HDPE films against external agents such as temperature and UV radiation has been corroborated. Finally, the processing window and the mechanical and thermal properties of PA1010 and bio-HDPE biopolymer blends have been greatly improved.