Examinando por Autor "Robledo, Nuria"

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Challenges and opportunities for recycled polyethylene fishing nets: towards a circular economy
(MDPI, 2021-09) Juan, Rafael; Domínguez, Carlos; Robledo, Nuria; Paredes, Beatriz; Galera, Sara; García-Muñoz, Rafael A.
Plastic waste generation has become an important problem that critically affects marine and oceans environments. Fishing nets gear usually have a relatively short lifespan, and are abandoned, discarded and lost, what makes them one of the largest generators of ocean plastic waste. Recycled polyolefin resins from fishing nets (rFN), especially from polyethylene (PE), have poor properties due to the presence of contaminants and/or excessive degradation after its lifetime. These reasons limit the use of these recycled resins. This work aims to study the incorporation of recycled fishing nets PE-made to different grades of virgin PE, in order to evaluate the potential use of these rFN in the development of new products. The recovered fishing nets have been fully characterized to evaluate its properties after the collection and recycling process. Then, different PE virgin resins have been mechanically blended with the recovered fishing nets at different recycling contents to study its feasibility for fishing nets or packaging applications. Critical mechanical properties for these applications, as the elongation at break, impact strength or environmental stress cracking resistance have been deeply evaluated. Results show important limitations for the manufacture of fibers from recycled PE fishing nets due to the presence of inorganic particles from the marine environment, which restricts the use of rFN for its original application. However, it is proved that a proper selection of PE raw resins, to be used in the blending process, allows other possible applications, such as non-food contact bottles, which open up new ways for using the fishing nets recyclates, in line with the objectives pursued by the Circular Economy of Plastics.
Incorporation of recycled high-density polyethylene to polyethylene pipe grade resins to increase close-loop recycling and Underpin the circular economy
(Elsevier, 2020-12) Juan, Rafael; Domínguez, Carlos; Robledo, Nuria; Paredes, Beatriz; García-Muñoz, Rafael A.
High-density polyethylene (HDPE) is one of the most used and demanded plastic, not only for packaging, but also for construction and within this application especially for non-pressure and pressure pipes, which makes this material the most abundant in the municipal waste stream. On the basis of the Circular Economy and the sustainable life that promotes, it is important to explore new applications for recycled HDPE (rHDPE) to increase the polymer recycled uptake. However, recycled HDPE is not currently being used in pressure pipes, mainly due to the high structural and loading requirements that must be met. The present study evaluates the potential use of post-consumer rHDPE from different origins in the manufacture of polyethylene pressure pipes. Different rHDPE sources are blended in different ratios with raw HDPE with PE100 grade quality. Blends are fully characterized to determine their feasibility to be used for pipe applications. Properties such as tensile strength at yield, elongation at break and flexural modulus for all blends yield values above the minimum required for PE100 grades. Furthermore, two important mechanical properties of polyethylene pipes, Slow Crack Growth (SCG) and Rapid Crack Propagation (RCP) resistances, are deeply evaluated. Remarkably, a dual correlation of SCG and RCP with the content of recycled PE in blends was established, allowing to develop predictive capabilities that guarantee the requirements and specifications for pressure pipe applications. Finally, through the evaluation of different waste streams, it can be concluded that handling, sorting, separation and selection of polyethylene’s waste is critical to achieve the required pipe specifications, and to increase the percentage of post-consumer rHDPE into the final product. This investigation is in line with the sustainability objective and the commitment to boost the circular economy by replacing part of the conventional HDPE raw material with recycled HDPE to increase close-loop recycling on PE for pipe application, and the basis for the recycling of rHDPE from pipe at its end-life, after 50 years in service.
Strain hardening test on the limits of the Slow Crack Growth evaluation in high resistance polyethylene resins: Effect of comonomer type
(Elsevier, 2020-01) Domínguez, Carlos; Robledo, Nuria; Paredes, Beatriz; García-Muñoz, Rafael A.
Long term performance assessment of polyethylene pipes is an issue that has greatly increased in importance in recent years due to the incorporation in the market of high resistance to crack polyethylene grades (PE100RC), where established Slow Crack Growth (SCG) evaluation using traditional tests such as Full Notch Creep Test (FNCT) or Pennsylvania Notch Tensile (PENT) Test is insufficient. The development in recent years of fast evaluation techniques such as Strain Hardening (SH) modulus has opened an important alternative for quick SCG evaluation since it correlates well with other conventional tests such as FNCT and PENT. In this work, a large number of commercial and experimental polyethylene pipe resins with different comonomer types were evaluated in order to define their SH values to rank the resins as PE100 or PE100RC. A relationship is proposed that utilizes SH test results to estimate the SCG resistance of PE pipes. 1-Butene copolymer resins display threshold SH values of 38 and 53 MPa that have been assigned to PE100 and 100RC grades, respectively. Moreover, dependence of the SH values on comonomer type used has been demonstrated. The experimental results show that 1-hexene copolymer resins exhibit higher SH values than 1-butene comonomer based resins.