Abstract

Abstract

Abstract

Composites based on epoxy resin are a class of high performance structural materials with great potential in a wide variety of industrial sectors. However, being thermoset resins, despite their great benefits in lightness and mechanical performance, they present the great disadvantage that once cured they can not be reprocessed, repaired or recycled. This is hindering the rapid growth of composite materials in applications such as automotive.

In order to overcome the disadvantages of thermosetting resins, this paper presents the development of a new generation of dynamic thermoset epoxy resins able to be reprocessed,  repaired and recycled thanks to the incorporation of reversible bonds within its reticulated structure. As resins containing dynamic bonds, the cured material presents new properties previously unthinkable for thermosetting materials. These new resins have been developed for the manufacture of composite materials reinforced with both glass fiber and carbon fiber. It has been shown that these new composites have mechanical properties equivalent to those of conventional thermosetting composites, but unlike the latter, they are recyclable, repairable and reprocessable, which is a step forward and the creation of new opportunities for sectors such as automotive .

Abstract

In this work the development of a profile manufactured by pultrusion and thereafter curved by thermoforming is presented. The pultrusion profile is based on a new thermostable epoxy resin with dynamic bonds capable of being reprocessed, repaired and recycled thanks to the incorporation of reversible links within its reticulated structure (3R Technology). Being a resin that contains dynamic bonds, the cured composite shows unexpected properties for thermosetting materials.

In a first phase, a new resin/hardener formulation processable by pultrusion with a viscosity, adhesion to the fibre and speed of curing similar to a conventional formulation have been developed and in a second phase, taking into account the properties of the new composite material, the parameters of the thermoforming process (pressure, temperature or speed of thermoforming) have been analysed and optimized.

Thanks to the combination of pultrusion and thermoforming processes, longitudinal 3R composite profiles acquire a new curved geometry defined by the design of a mould. In this way, the thermoforming of the straight profiles will allow manufacturing curved parts from profiles of thermostable composites with high mechanical performance manufactured by pultrusion in medium-high rates, typical of the automotive sector. Additionally, it will be shown that the profiles manufactured using these composites can be recycled, reducing the amount of waste generated and offering these materials a second useful life.

Abstract

Composites based on epoxy resin are a class of high performance structural materials with great potential in a wide variety of industrial sectors. However, being thermoset resins, despite their great benefits in lightness and mechanical performance, they present the great disadvantage that once cured they can not be reprocessed, repaired or recycled. This is hindering the rapid growth of composite materials in applications such as automotive. In order to overcome the disadvantages of thermosetting resins, this paper presents the development of a new generation of dynamic thermoset epoxy resins able to be reprocessed,  repaired and recycled thanks to the incorporation of reversible bonds within its reticulated structure. As resins containing dynamic bonds, the cured material presents new properties previously unthinkable for thermosetting materials. These new resins have been developed for the manufacture of composite materials reinforced with both glass fiber and carbon fiber. It has been shown that these new composites have mechanical properties equivalent to those of conventional thermosetting composites, but unlike the latter, they are recyclable, repairable and reprocessable, which is a step forward and the creation of new opportunities for sectors such as automotive .

Abstract

This work is focus on the development of photocurable resins doped with nanoparticles of very diverse nature, diamond, barium oxide, hydroxyapatite and silver. These nanoreinforcements are being investigated, and even applied industrially, as nanofillers of thermosetting resins, due to the different enhancements and new properties, including increased mechanical, thermal and chemical properties, high electrical and thermal conductivity, improved biocompatibility and antimicrobial properties, among others. The reinforcement of photocurable thermosetting resins can be complex since the added charge can exert shielding to the radiation, limiting to reach high curing degree. For it, it is necessary to use catalysts and sensitizers of UV radiation. In addition, in order to limit this negative effect, a high degree of dispersion of the nanofillers is required, avoiding the presence of micrometric agglomerates. An epoxy system has been selected, whose is commly used for dental applications, and differente contents of nanofillers have been added. Once the dispersion process has been optimized, the effect of the different fillers on the degree of curing of the photocurable resin, measured through its glass transition temperature, has been studied. The degree of curing achieved has been explained through transperance measurements to the visible light of the samples, as well as the morphology of the cured and doped resins.

Abstract

The idea of ​​recycling waste materials from such different sectors as textile or  automotive has been popular for decades, but today's recycling methods often produce poor quality products that are difficult to reuse. In the specific case of thermoset composites the problem is even greater, since once the resin is cured its dissolution is not possible and therefore the recovery of the original fiber and resin becomes practically unfeasible. This work presents recyclable thermoset composites made with fabrics obtained from waste textiles and epoxy or polyurethane resins, whose crosslinking is based on reversible bonds, which confers them the ability to be dissolved in a specific agent, so that both the fiber and the resin can be recovered for subsequent reuse. Taking into account the particularities of the starting raw materials, the manufacturing parameters of the composites and the resin dissolution conditions have been studied and optimized. The work is part of the European project Trash-2-Cash, which proposes a new model in which waste from paper and textiles are recycled chemically,in order to obtain fabrics with the same quality as the initial ones, to manufacture innovative products such as recyclable thermoset composites that can be industrially produced and recycled at the end of life.

Abstract

This work presents the effect of hydrothermal aging in distilled water on several epoxy  hybrid materials that have a certain amount of carbon nanotubes and/or graphene nanoplatelets. Two types of graphene nanoplatelets have been used: amino functionalized graphene (GNH2) and non functionalized graphene. When functionalized graphene is used, covalent bonds between the graphene nanoplatelets and the epoxy matrix are expected to be formed over the curing process. Non functionalized graphene platelets are used to prove this effect. Gravimetric study of the absorption process has been done as well as the effect of the water absorption on the thermo-mechanical properties and the electric conductivity.

Abstract

Although Bisphenol A content in epoxy resins based on it (called Bisphenol A diglycidyl ethers, BADGE) is practically undetectable using nowadays analytical techniques, Bisphenol A is a controversial product due to its toxicology. For this reason, epoxy resins in general and composite epoxy matrices in particular are in focus of scientific and social media. We studied several alternatives both petroleum-based (e.g. trimethylolpropane or entaerythritol) and bio-based (e.g. isosorbide, lignin or sorbitol). The main objective of these BADGE alternatives is to obtain products that could be adapted to the requirements of the composite market with minor differences respect to Bisphenol A epoxy derivatives in morphological, chemical, mechanical and thermal properties.

Abstract

The objective of the AIRPOXY project is to reduce production and maintenance, repair & operating (MRO) costs of composite parts in aeronautics, by introducing a new family of enhanced thermoset composites that preserve all the advantages of conventional thermosets, while show unprecedented new features such as Re-processability, Repairability and Recyclability. This new generation of composites, called 3R composites, are obtained using dynamic hardeners which create reversible crosslinks in the cured epoxy resin. Once the 3R composite has been produced, the dynamic chemical bonds in the cured resin can be reshuffled under determined external stimulus, such as temperature or exposure to a specific chemical agent.

The study describes the development of a first version of 3R composite that meets the requirements of the aeronautical sector. Firstly the resin has been formulated, then the composite laminates have been produced by Resin Transfer Moulding (RTM) and finally their dynamic and mechanical properties have been studied.