Examinando por Autor "Navas-Martos, Francisco"
Mostrando 1 - 2 de 2
- Resultados por página
- Opciones de ordenación
Ítem Characterization of Cellulosic Pulps Isolated from Two Widespread AgriculturalWastes: Cotton and Sunflower Stalks(MDPI, 2024-06-04) la-Rubia, María Dolores; Jurado-Contreras, Sofía; Navas-Martos, Francisco; García-Ruiz, Ángeles; Morillas-Gutiérrez, Francisca; Moya-López, Alberto José; Mateo, Soledad; Rodríguez-Liébana, José AntonioGlobally, huge amounts of cotton and sunflower stalks are generated annually. These wastes are being underutilized since they are mostly burned in the fields. So, in this work, we proposed a three-step method consisting of acid pre-treatment, alkaline hydrolysis, and bleaching for the extraction of cellulose pulps. These pulps were characterized to assess their morpho-structural and thermal properties. The design of experiments and response surface methodology were used for the optimization of the acid pre-treatment in order to achieve maximum removal of non-cellulosic compounds and obtain pulps enriched in cellulose. For cotton stalks, optimal conditions were identified as a reaction time of 190 min, a reaction temperature of 96.2 ◦C, and an acid (nitric acid) concentration of 6.3%. For sunflower stalks, the optimized time, temperature, and acid concentration were 130 min, 73.8 ◦C, and 8.7%, respectively. The pulps obtained after bleaching contained more than 90% cellulose. However, special care must be taken during the process, especially in the acid pre-treatment, as it causes the solubilization of a great amount of material. The characterization revealed that the extraction process led to cellulose pulps with around 69–70% crystallinity and thermal stability in the range of 340–350 ◦C, ready to be used for their conversion into derivatives for industrial applications.Ítem Manufacture and Characterization of Recycled Polypropylene and Olive Pits Biocomposites(MDPI, 2022-10-07) Jurado-Contreras, Sofia; Navas-Martos, Francisco; Rodríguez-Liébana, José A.; Moya, Alberto J.; La Rubia, M.DoloresThe present work studies the use of olive pit (OP) as a reinforcement in the manufacture of composites based on a post-consumer recycled polypropylene (rPP). In this way, it is feasible to provide added value from olive pits, a by-product resulting from the olive industry operations, while promoting the circular economy and reducing the use of fossil-based polymers. For this purpose, suitable samples were manufactured using 25 wt% and 40 wt% of OP. Additionally, the effect of incorporating additives was studied: (a) a process control additive (PA), and (b) a coupling agent of maleic anhydride grafted polypropylene (MAPP). The results showed an improvement in Young’s and flexural modulus with the OP addition. The incorporation of PA did not present any significant improvement in the properties of the materials, nevertheless it facilitated the biocomposite manufacturing process. As for the coupling agent, it significantly improved the mechanical properties, achieving the best results with the addition of the two types of additives and 40 wt% of OP. Moreover, the thermal properties were maintained, and there was an increase in crystallinity in all composites compared to rPP. According to the results of the fracture surface analysis, the coupling agent improves reinforcement-polymer matrix cohesion.