Documents published in Scipedia

• Bio-based recyclable crosslinked polyurethanes based on a thermally reversible Diels-Alder adduct

  A. Restrepo Montoya, I. Larraza, K. Gonzalez, O. Echeverria Altuna, I. Harismendy, A. Saralegi, A. Eceiza

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 4 - Sostenibilidad y Reciclaje), 15

  
  

  Abstract

  Thermosets comprise a family of chemically cross-linked networks formed by irreversible chemical reactions, resulting in polymers with outstanding properties such as superior mechanical properties, high thermal stability and chemical resistance. However, their high stability precludes reprocessing or recycling, thus making it difficult to move towards a circular economy and sustainability. During the last years, research has focused on dynamic chemistry, in order to introduce reversible bonds along the polymer chain and synthesize reprocessable and/or recyclable thermosets. In this context, the Diels-Alder reaction is of special interest, as it can give thermoreversible reactions with a relatively low coupling and high decoupling temperature. Within this work, a trifunctional polyol containing the furan-maleimide Diels-Alder adduct has been developed to facilitate the recycling of cross-linked polyurethanes. The maleimide-furan adduct forms covalent bonds at low temperatures, but when heated these bonds break down, splitting the polymer chain into smaller chains and softening the polymer, allowing it to be reprocessed. Then, when the temperature drops, the bonds between the maleimide and the furan are reformed and the polymer regains its mechanical properties. Thereby, a thermoset polyurethane was synthesized reacting the triol containing Diels-Alder adduct with a polymeric isocyanate. The reprocessability and/or recyclability of the synthesized polyurethane was then evaluated by breaking it into small pieces and reprocessing them by pressing at high temperature, in order to obtain new sheets and evaluate their mechanical properties, being similar to the original ones.

  Abstract
  Thermosets comprise a family of chemically cross-linked networks formed by irreversible chemical reactions, resulting in polymers with outstanding properties such as superior [...]

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• Synthesis of hybrid acrylic-polyurethane biobased systems for adhesive applications

  O. Echeverria Altuna, I. Calafel, R. Rodriguez, N. Fernandez

  Materiales Compuestos (Online first).

  
  

  Abstract

  Hybrid acrylic/water-based polyurethane systems have been synthesized by a polymerization process in which acrylic monomers have been used as solvents in polyurethane systems. The polymerization has been carried out in four main stages The first stage in which a prepolymer has been obtained, a second stage in which the chain extension has been carried out. In the third stage has obtained the phase inversion and finally in the last stage has been carried out the synthesis of acrylic monomers. Polymerization was monitored by ATR-FTIR and gravimetry. The effect of incorporating a bifunctional chain extender and replacing a conventional PPG polyol with two types of commercial biopolyols (Priplast 1900, 48% renewable and Priplast 3294, 100% renewable) was analyzed. It has been proven that the addition of a second bifunctional chain extender improves the adhesive properties of the hybrid system, an effect that is enhanced by the use of biopolyols. It has been proven that the use of bio-based polyols is possible since they do not significantly reduce thermal properties, making it feasible to obtain a material with 20% renewable content.

  Abstract
  Hybrid acrylic/water-based polyurethane systems have been synthesized by a polymerization process in which acrylic monomers have been used as solvents in polyurethane systems. [...]

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• Thermoset polyurethanes based on recycled and biobased constituents

  E. Mendiburu-Valor, I. Larraza, O. Echeverria Altuna, I. Harismendy, A. Eceiza

  Materiales Compuestos (2024). Vol. 08 - COMUNICACIONES MATCOMP21 (2022) Y MATCOMP23 (2023), (Núm. 4 - Sostenibilidad y Reciclaje), 21

  
  

  Abstract

  Poly(ethylene terephthalate) (PET) is one of the most consumed plastics in the world, so it is very common to find it in the sea or ocean. Thermomechanical recycling is normally used for urban and industrial PET waste, but it is not suitable for highly degraded marine litter. Chemical recycling of marine PET litter is presented as an alternative for the valorization of this highly degraded waste. The bis(2-hydroxyethyl) terephthalate (BHET) monomer obtained can be used in the synthesis of new polymers. This study explores the potential of using BHET for the synthesis of high modulus and high strength thermoset polyurethanes. In addition, a renewable reagent, such as a polyol derived from castor oil, has been used to synthesize a recycled and biobased polyurethane thermoset (BHET-BioPU). The resulting BHET-BioPU has been thermally, thermo-mechanically and mechanically characterized to evaluate its potential applications. In addition, the recyclability by glycolysis of the BHET-BioPU has been demonstrated, thus advancing towards a circular economy. The results of this study provide fundamental knowledge for the development of sustainable, environmentally friendly and high performance materials and recyclable as well, materials, and represent an important achievement in the global effort to reduce dependence of fossil resources and plastic pollution.

  Abstract
  Poly(ethylene terephthalate) (PET) is one of the most consumed plastics in the world, so it is very common to find it in the sea or ocean. Thermomechanical recycling is normally [...]

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• NEW SUSTAINABLE BIO-PUR FORMULATIONS FOR OFFSHORE RENEWABLE ENERGY

  O. Echeverria Altuna, O. Ollo, I. Larraza, I. Harismendy, A. Eceiza

  Materiales Compuestos (Online first).

  
  

  Abstract

  The development of sustainable composites has become in a major strategy for different sectors, such as the offshore renewable energy industry. Thermoset polyurethanes (PUR) offer some advantages for their use in structural composite parts, like their good thermal properties, adhesion with different types of fibers, ultra-fast curing, low viscosity and corrosion resistance, highlighting their resistance to fatigue and consequent durability. However, PUR have some environmental drawbacks, such as their petrochemical origin and low recyclability. Consequently, biobased PUR (BIO-PUR) formulated based on polyols derived from vegetable oils have aroused keen interest. Moreover, it is possible to incorporate recycled monomers in their formulation, which are obtained from highly degraded plastics collected from the sea. In addition, it is necessary to consider the PUR end of life to improve the composite sustainability. An interesting solution is the incorporation of dynamic bonds into the PUR network, with reversible capacity such as Diels-Alder, to improve the polymer recyclability. Therefore, this work has focused on the development of a new formulation of BIO-PUR with the required mechanical properties for structural applications in the marine environment. In addition, the integration of recycled monomers and DA bonds have been explored to improve the circularity of the developed resin. To this end, aspects ranging from analysis and synthesis to the characterization of the resins have been covered.

  Abstract
  The development of sustainable composites has become in a major strategy for different sectors, such as the offshore renewable energy industry. Thermoset polyurethanes [...]

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• Development of more sustainable PUR formulations for structural applications

  O. Echeverria Altuna, O. Ollo, I. Harismendy, A. Eceiza

  Materiales Compuestos (2023). Vol. 07 - COMUNICACIONES MATCOMP21 (2022), (Núm. 3 - Materiales y Estructuras - Modelos Numéricos), 9

  
  

  Abstract

  The industry decarbonization has become in a fundamental challenge for the industries such as automotive or wind power. In this way, the structural components lightening is one of the principal issues for material manufacturers. For this objective, the composites are a competitive alternative, due to their unique relation between their strength and weight. Among the different structural composite part fabrication processes, liquid composite moulding (LCM) is one of the most interesting, due to its efficiency in terms of costs, time and energy consumption. In this sense, resins with fast cure and low viscosity are gaining attention, among them polyurethanes are of particular interest. This family of polymers is characterized by its great versatility, among them high-performance thermosetting polyurethanes (PUR). The advantages offered by PUR-based technology are great fatigue resistance, low viscosity and fast cure. However, the commonly used PUR’s for structural applications have some environmentally drawbacks, such as their components petrochemical origin and their low recyclability. For this reason, the aim of this work was the development of a more sustainable PUR formulation with the required mechanical properties for structural applications and suitable processability for LCM processes. Because of that, this work has focused on the analysis, synthesis and characterization of new PUR formulations and also the manufacturing process simulation and optimization.

  Abstract
  The industry decarbonization has become in a fundamental challenge for the industries such as automotive or wind power. In this way, the structural components lightening is [...]

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