Documents published in Scipedia

• CHAPTER 17: VITRIMERS

  N. Markaide, A. Ruiz

  libro-blanco-materiales-compuestos (2024). 41

  
  

  Abstract

  The development of recyclable plastics is a key focus of research in the current world due to its environmental issues and concerns about non-renewability. Recently, vitrimeric materials have garnered significant attention as an exciting class of renewable plastics due to their potential to exhibit strength, durability, and chemical resistance approaching that of traditional thermosetting plastics, while also demonstrating recyclability at the end of their lifespan. This is attributed to their chemical structure, as vitrimers possess dynamic covalent crosslinking, providing them with stability while being reprocessable. This review summarizes the latest advancements and prospects in the development of vitrimeric materials. Special emphasis is placed on vitrimer design strategies that pave the way for the development of next-generation circular materials. The emerging applications of vitrimers are also discussed in terms of their properties, including self-repair, malleability, processability, and multiple shape memory.

  Abstract
  The development of recyclable plastics is a key focus of research in the current world due to its environmental issues and concerns about non-renewability. Recently, vitrimeric [...]

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• CHAPTER 16: BIO-MONOMERS AND THERMOSTABLE BIO-RESINS

  S. Prolongo, A. Suárez

  libro-blanco-materiales-compuestos (2024). 42

  
  

  Abstract

  Thermosetting resins, especially epoxy resins, have historically been based on petroleum-derived monomers, posing problems of toxicity, high costs, and dependence on non-renewable resources. This chapter presents the use of natural plant sources to develop more sustainable resin precursors. The synthesis of bio-epoxy monomers from vegetable oils, polysaccharides, lignin, polyphenols, and natural resins is currently the subject of interest in several research projects and scientific papers, in some cases reaching the level of product commercialization. Vegetable oils, such as linseed and soybean, and the transformation of saccharides into epoxy monomers are examples of explored options. Naturally occurring epoxy monomers derived from polyphenols from various plant sources can also be found, although their epoxidation requires the use of toxic compounds such as epichlorohydrin. Several natural sources, such as natural rubber, resin acids, and lignin are examined as alternatives to synthesize epoxy resins of natural origin. Leutelin, recently identified in fruits and medicinal herbs, is highlighted as a promising compound to produce bioepoxy monomers. Although initially the research focused mostly on the development of monomers of natural origin, research also extends to hardeners of natural origin, highlighting the synthesis of amines from vanillin and curing agents based on phenalkamines. The development of hardeners with reversible bonds, such as lignin imines, is also being explored, and the catalytic effect of hemp fibers in the curing of epoxy resins is highlighted. The combination with traditional monomers or the development of recyclable resins and vitrimers with reversible bonds are current fields of interest for the development of these resins, especially in the context of their competitors of petrochemical origin.

  Abstract
  Thermosetting resins, especially epoxy resins, have historically been based on petroleum-derived monomers, posing problems of toxicity, high costs, and dependence on non-renewable [...]

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• CHAPTER 15: REUSE OF FIBERS AND RESINS IN STRUCTURAL ELEMENTS. PROPOSALS FOR USE IN DIFFERENT INDUSTRIES: PRELIMINARY PROPOSALS FOR USE

  R. Vera

  libro-blanco-materiales-compuestos (2024). 43

  
  

  Abstract

  One of the main problems of composite recyclability, is to find applications with a positive business case and technically viable. In order to determine possibilities, it is necessary, first, to analyze mechanical properties of materials as well as today available manufacturing processes with this type of products.

  Abstract
  One of the main problems of composite recyclability, is to find applications with a positive business case and technically viable. In order to determine possibilities, it [...]

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• CHAPTER 13: WASTE MANAGEMENT AND REUSE TECHNOLOGIES OF NON-POLYMERIZED COMPOSITE MATERIALS

  N. Martín, Á. Casanova

  libro-blanco-materiales-compuestos (2024). 45

  
  

  Abstract

  This chapter addresses two relevant challenges to enforce in a manufacturing plant where carbon fiber prepreg is used as raw material for the manufacture of aeronautical parts. The first challenge is the segregation of fresh production waste, where the resin is fresh and has a big potential for being used as material for other applications. This chapter described a proposal for the collection of this highly valuable material in a pilot plant where aircraft stabilizers are manufactured. This second challenge addresses solutions for the reprocessing of waste material discarded during the manufacturing of carbon parts. Hereafter is described the preparation of new materials or by-products, which can be reincorporated into the production system of other composite material parts.

  Abstract
  This chapter addresses two relevant challenges to enforce in a manufacturing plant where carbon fiber prepreg is used as raw material for the manufacture of aeronautical parts. [...]

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• CHAPTER 10: MECHANICAL RECYCLING OF COMPOSITE MATERIALS

  S. Prolongo, A. Suárez

  libro-blanco-materiales-compuestos (2024). 48

  
  

  Abstract

  The mechanical recycling of long-fiber composite materials is presented as an alternative of greater technological simplicity as well as low energy consumption, emission of pollutants and use of solvents, which places it in an advantageous position from the point of view of environmental sustainability. However, the products obtained are short-fibered, which reduces their mechanical reinforcement capacity, and have been used mainly as fillers for cementitious, asphalt and thermoplastic matrices.  The technologies used to reduce the size of the initial pieces substantially influence the characteristics of the final product obtained, especially if they are to be used for functional purposes in terms of electrical or thermal properties. In addition, the fibers obtained have a proportion of resin from the initial composite material, so the subsequent treatment processes of these fibers, both physical and chemical, can affect the amount of final resin present in the product, its agglomeration or its surface characteristics.  The current challenges for these products is to find processes that allow a better quality and greater uniformity of the final properties of the short fiber, so that the products obtained present a greater added value, which allows them to compete with other current discontinuous reinforcements.

  Abstract
  The mechanical recycling of long-fiber composite materials is presented as an alternative of greater technological simplicity as well as low energy consumption, emission of [...]

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• CHAPTER 12: WASTE REDUCTION IN PRODUCTION AND REUSE OF MATERIALS

  L. Coronado, I. Raboso

  libro-blanco-materiales-compuestos (2024). 46

  
  

  Abstract

  The efforts to reduce, reuse and recycle scrap derived from manufacturing processes with composite materials are significantly increasing in all those sectors making use of such materials in their production systems. The rising commitment with the environmental cause and the everyday stricter regulation in terms of waste management has led to launching new initiatives  to minimize the environmental impact  of composite materials and derived components manufacturing. Therefore, the aim of this chapter is to provide several examples of optimization initiatives in the use of composite materials and, consequently, the reduction and reuse of waste in production environments in the aeronautical sector, having Airbus as a reference where, according to the available pre-pandemic data, 61% of the scrap corresponds to uncured material whereas 39% refers to cured waste.

  Abstract
  The efforts to reduce, reuse and recycle scrap derived from manufacturing processes with composite materials are significantly increasing in all those sectors making use of [...]

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• CAPÍTULO 11: TECNOLOGÍAS DESTINADAS A LA REUTILIZACIÓN DE FIBRAS CORTAS DE VIDRIO Y CARBONO RECICLADAS

  J. Navarro, L. Quilez", B. Bas

  libro-blanco-materiales-compuestos (2024). 47

  
  

  Abstract

  En este capítulo se describen las diferentes estrategias de reutilización que se pueden llevar a cabo con los materiales compuestos con matrices poliméricas una vez pasados por los centros de reciclaje actualmente disponibles a escala industrial.  El trabajo describe cómo, dependiendo de la naturaleza tanto de las matrices como de las fibras de refuerzo, la reutilización de este tipo de fibras debe estar dirigida hacía un tipo de procesos u otros y cómo, mediante la variación de las tecnologías, es posible dar lugar a productos con una mayor o menor orientación de las fibras. De la misma manera, el capítulo analiza algunos de los procesos de fabricación de materiales compuestos, que pueden afectar a la longitud de las fibras y por lo tanto modificar las propiedades del material final.  De esta forma, se describen las diferentes tecnologías actualmente disponibles y en proceso de desarrollo en España para poder dar una nueva vida a las fibras de carbono y de vidrio, orientadas a retener la mayor parte de su valor añadido y propiedades, como son: reutilización en materiales compuestos termoestables, reutilización como refuerzo en materiales compuestos termoplásticos, reprocesado de la fibra (estructuras de fibra tejidas o no tejidas), reciclado de fibras que todavía estén embebidas, reciclajes específicos según la naturaleza de la fibra.  A lo largo del texto se van recogiendo algunos de los proyectos liderados por entidades españolas con mayor relevancia en el desarrollo de las diferentes tecnologías y, además, al final del mismo se remarcan esos mismos proyectos y otros más en los que se destaca el trabajo realizado por centros, universidades y empresas españolas en el campo de la reutilización y reciclaje de fibras de carbono y de vidrio.  

  Abstract
  En este capítulo se describen las diferentes estrategias de reutilización que se pueden llevar a cabo con los materiales compuestos con matrices poliméricas [...]

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• CHAPTER 9: SOLVOLYSIS AND BIOLOGICAL RECYCLING OF COMPOSITES. OBTAINING RAW MATERIALS

  P. Aguar, N. Miazza

  libro-blanco-materiales-compuestos (2024). 49

  
  

  Abstract

  This chapter analyses the chemical recycling technique by solvolysis and by biological recycling, explaining that it involves breaking the polymer chain by using reactive solvents, temperature, catalysts, and pressure in the first case, and enzymes and microorganisms in the second. The situation of both technologies is shown, i.e. the operating parameters found in the literature for each type of polymer. In the case of solvolysis, the companies that are currently commercializing this technology are listed; there are still no companies for the case of biological recycling as its technology readiness level (TRL) is lower than for solvolysis. The chapter ends with recommendations for future developments for both types of solvolysis.

  Abstract
  This chapter analyses the chemical recycling technique by solvolysis and by biological recycling, explaining that it involves breaking the polymer chain by using reactive [...]

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• CHAPTER 8: REVALUATION OF PYROLYSIS PRODUCTS

  A. Lopez-Urionabarrenechea, A. Serras-Malillos, N. Gastelu, B. Perez-Martinez, E. Acha, B. Caballero, I. Marco

  libro-blanco-materiales-compuestos (2024). 50

  
  

  Abstract

  This chapter describes the physical-chemical properties and market options of pyrolysis oils and pyrolysis gases coming from residual fiber-reinforced plastic materials. The description focuses on the pyrolysis products generated from the two predominant types of resin in these materials, i.e. epoxy and unsaturated polyester, from both production and end-of-life waste. Pyrolysis oils and gases have two potential industrial applications: the petroleum refining and petrochemical industries, and the alternative fuels market, namely, refuse derived fuels (RDF). However, it can be observed throughout the chapter that the physical-chemical properties of these two products are far from the standards currently required by the industry. Finally, the state of the art of the research on the optimization possibilities of these products is presented, highlighting a successful case where the oils are eliminated and hydrogen-rich gases are generated, increasing the economic profitability of the pyrolysis processes applied to this kind of waste.

  Abstract
  This chapter describes the physical-chemical properties and market options of pyrolysis oils and pyrolysis gases coming from residual fiber-reinforced plastic materials. The [...]

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• CHAPTER 7: RECYCLING AND RECOVERY TECHNOLOGIES OF CARBON AND GLASS FIBERS BY PYROLYSIS

  O. Rodriguez Largo, F. A.López

  libro-blanco-materiales-compuestos (2024). 51

  
  

  Abstract

  Of all the recycling technologies available for recycling fiber-reinforced composite materials, pyrolysis is one of the most frequently used. This technology allows the recovery of long fibers with good mechanical properties in addition to reusing the resin in the form of energy. This chapter describes this technology, including some variations of it, such as microwave-assisted pyrolysis. It can be concluded that pyrolysis is a suitable technology for the recovery of long fibers, maintaining between 70-95% of their initial mechanical properties. Furthermore, pyrolysis applied to reinforced composites is a technology currently used at an industrial level, both in Europe and in Spain.

  Abstract
  Of all the recycling technologies available for recycling fiber-reinforced composite materials, pyrolysis is one of the most frequently used. This technology allows the recovery [...]

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