Tag: thermal properties

Innovation in the production of composite materials: the use of graphene in pultrusion

Posted on | by Energeia Graphenemex

Innovation in the production of composite materials:

the use of graphene in pultrusion

Fiber-reinforced polymeric composites are widely used in the aerospace, automotive, naval, and wind power generation sectors due to their lightweight properties and high mechanical strength. These materials are a booming alternative to replace other materials such as metals.

At present there are different methods for the manufacture of fiber-reinforced composites, among which the pultrusion method stands out. A highly efficient and automated method that allows control of process parameters (greater precision and accuracy), reducing variability in the production of parts.

Pultrusion is a production process for reinforced materials where two components can be distinguished, the matrix or continuous phase and the reinforcement or discontinuous phase. The matrix acts as a bonding agent, in which the reinforcement is embedded. The function of the matrix is to transfer the load to the fibers, keep the fibers in their position, prevent the propagation of cracks, provide physical and chemical properties of the composite and also define the temperature range that the composite material can withstand. The matrix is thermosetting or thermosetting (unsaturated polyester, epoxy resins or vinyl-ester resins). On the other hand, the reinforcement has the purpose of adding some property that the matrix does not have, such as increasing mechanical resistance, rigidity, resistance to abrasion or improving its performance when exposed to high temperatures. The reinforcement efficiency is greater, the smaller the size of the particles or the diameter of the fiber and the more homogeneously they are distributed in the matrix. The most used fibers are glass, carbon and aramid due to their high tensile strength.

The pultrusion process (Figure 1) is continuous and is used to manufacture parts with a constant cross section, such as poles, rods, automotive moldings, etc. In the first feeding stage, the reinforcing fibers go through a perforated plate for alignment, then they go through a pre-molding where a fabric is added to reinforce the fiber. Later, in the second stage, the fibers are impregnated with liquid resin and go to a pre-forming stage where the fibers are oriented before entering the mold. In the third stage (molding), the cross section of the part is shaped, and the resin is hardened by applying heat. During the application of heat in the mold, there are three phases: pre-heating of the matrix and reinforcement, activation of the polymerization catalyst and curing of the material. The profile then exits the mold as a thermoset material and passes into a continuous traction mechanism that pulls the material at a constant speed (fourth stage)). Finally, in the fifth stage, a disk saw cuts the profile to the desired length. The profile of the reinforced composite obtained is a completely rigid material, which does not soften and is insoluble with the ability to withstand high temperatures.

Figure 1. General scheme of the pultrusion process: (1) Feeding, (2) Impregnation, (3) Molding, (4) Traction device and (5) Saw (Cutting).

Currently, the main applications of this process are focused on the manufacture of materials for construction, transport, and consumables, for example: vehicle construction, thermal insulation, cable ducts, covers and grids for water treatment plants, beam profiles, building facades, windows, bridges, stairs, among others.

However, there are still limitations in this technology, the low chemical interaction of the fiber with the matrix (resin) leads to a weak interface bond strength between both phases (low chemical adhesion), which makes the behavior of interlaminar shearing and performance of composite materials is not entirely satisfactory. In other words, if the matrix is brittle, spontaneous rupture can be generated. This behavior makes it possible to measure the resistance to interlaminar shearing. Depending on the type of break, the resistance of the matrix material or the quality of the fiber-matrix bond can be characterized.

In recent years, it has been reported that the introduction of functionalized graphene oxide (GO) on the surface of the fibers is an effective method to improve the interfacial properties of composite materials, since the large surface area of graphene oxide allows covering the surface of the fibers, increasing the strength of the chemical bond between the fiber and the matrix, thus improving the mechanical resistance of the reinforced composites. In addition, graphene oxide helps to improve the resistance to interlaminar fracture of the composite material, inhibiting the initiation and propagation of cracks.

The addition of graphene oxide to reinforced polymeric composites offers numerous advantages for the development of advanced materials in a wide variety of applications due to its large surface area, which has a strong impact on mechanical strength properties, greatly improving properties such as modulus, toughness, and fatigue. On the other hand, graphene oxide can provide compounds with greater resistance to fire. Its efficiency is associated with the fact that graphene oxide has a strong barrier effect, high thermal stability, and great surface absorption capacity, which are favorable for effectively reducing heat and mass transfer.

Currently, Energeia – Graphenemex®, a leading Mexican company in Latin America in the research and production of graphene materials for the development of applications at an industrial level, sells graphene and graphene oxide that can be incorporated or dispersed in any matrix (resin) during the pultrusion process and with them improve the mechanical properties of the profiles or products.

The incorporation of graphene materials (graphene, graphene oxide) in the pultrusion process, provide improvements in the characteristics of the final product, which include:

  • Greater tensile strength. Tensile strength can increase up to 30% compared to a standard profile without graphene.
  • Production of lighter weight profiles since graphene allows the weight of the product to be reduced without affecting its mechanical properties.
  • Profiles with higher modulus of elasticity.
  • Greater resistance to corrosion and fire-retardant properties.
  • Greater resistance to fractures or fissures.

References

  1. Yuxin He, Qiuyu Chen. Effect of multiscale reinforcement by fiber surface treatment with polyvinyl alcohol/graphene oxide/oxidized carbon nanotubes on the mechanical properties of reinforced hybrid fiber composites. Composites Science and Technology 204 (2021).108634.
  2. Jonas H. M. Stiller, Kristina Roder, David Lopitz. Combining Pultrusion with carbonization: Process Analysis and materials properties of CFRP. Ceramics 2023, 6. 330-341.
  3. Dittrich B, Wartig K-A, Hofmann D, Mu¨lhaupt R, Schartel B. Flame retardancy through carbon nanomaterials: carbon black, multiwall nanotubes, expanded graphite, multi-layer graphene and graphene in polypropylene. Polym Degrad Stab 98:1495.

Improve safety with flame retardant polymeric compounds with graphene oxide

Posted on | by Energeia Graphenemex

Improve safety with flame retardant polymeric compounds

with graphene oxide

Polymeric compounds (engineering plastics) are widely used in the automotive, construction, food, aerospace and other sectors. Its use is based on the weight/resistance ratio, physical stability, chemical resistance and corrosion resistance.

However, most polymers, due to their nature, are flammable and combustible. That is, they are materials that catch fire quickly when exposed to fire, undergoing degradation, Veo complicadoand releasing heat to later start the propagation of the flames. During the combustion of polymers, they release smoke (soot) and toxic gases that are a danger to the safety of human life and property.

Four key components are involved during the combustion of polymeric materials: heat, oxygen, fuel, and free radical reaction. Flame retardancy of polymeric composites can be achieved by inhibiting or perturbing one or more of these components.

In recent years, multiple investigations have been carried out to develop additives that help inhibit or reduce the flammability of polymers, these additives are known as flame retardants.

Conventional flame retardants can be classified into two main categories, based on their components: inorganic flame retardants and organic flame retardants. The first include hydroxide, metal oxide, phosphate, silicate among others. They have excellent thermal stability, are non-toxic, are low cost and do not produce pollution. However, inorganic flame retardants are limited by high loading, low compatibility, and aggregation. On the other hand, organic flame retardants include flame retardants containing halogens, phosphorous, phosphorous-nitrogen, etc. The latter have high efficiency and good compatibility with polymers. Their main disadvantage is that they are restricted because they can release toxic gases and be harmful during combustion, endangering the health of people and the environment.

Graphene oxide (GO) is currently the most novel nanomaterial for use as a flame retardant because it exhibits high efficiency as a retardant with low loads and is non-toxic. Its efficiency is associated with the fact that graphene oxide has a strong barrier effect, high thermal stability and great surface absorption capacity, which are favorable for reducing heat and mass transfer.

Graphene-based flame retardants can improve the flame resistance of polymers by inhibiting the two key terms: heat and fuel. More specifically, graphene oxide can function as a flame retardant in different synergistic ways.

  1. First of all, GO has a unique two-dimensional layer structure and can promote the formation of a continuous dense layer of carbon during the combustion process. Carbon can act as a physical barrier to prevent heat transfer from the heat source and delay the escape of products (pyrolysis) from the polymeric substrate.
  2. Second, GO has a large specific surface area and can effectively adsorb flammable volatile organic compounds or hinder their release and diffusion during combustion.
  3. Third, GO contains abundant reactive oxygen-containing groups (carboxyl group at the edges, as well as epoxy and hydroxyl groups at the basal planes in the sheets). For example, oxygen-containing groups can undergo decomposition and dehydration at low temperatures, thus absorbing heat and cooling the polymeric substrate during combustion. Meanwhile, the gases generated by dehydration can dilute the oxygen concentration around the ignition periphery, decreasing the risk of fire spread.
  4. It can also modify the rheological behavior of the polymer and prevent its dripping, thus hindering the release and diffusion of volatile decomposition products through the ”maze effect” and affecting the flame retardancy of compounds (for example, modifying the UL-94 classification, oxygen index (OI) and time to ignition (TTI).

In studies carried out, it has been found that the incorporation of functionalized graphene oxide (5% by weight) in Polypropylene (PP) increased the Young’s modulus and the elastic limit of PP by 53% and 11%, respectively. While in the results of the flammability test (UL-94), it indicates that the presence of GO produces a change in the behavior of the melt and prevents the material from dripping.

On the other hand, the preparation of polymeric compounds in melt blending (extrusion) of Polystyrene/GO have been reported, where it was found that GO (5%) can promote carbonization on the polymer surface (layer of carbonized material). and inside, the presence of a load or filler that presents high resistance to heat and contributes to the formation of carbon residues, improving the flame resistance of polystyrene-based compounds.

Currently Energeia – Graphenemex®, a leading Mexican company in Latin America in research and production of graphene materials for the development of applications at an industrial level, through its Graphenergy Masterbatch line, has developed a wide range of masterbatches with graphene oxide, based on various polymers, such as PP, HDPE, LDPE, PET and PA6.

The incorporation of graphene and graphene derivatives (GO) to polymeric matrices has allowed the development of polymeric compounds with better mechanical properties, greater thermal stability, gas barrier capacity and reduced flammability of polymeric compounds.

References

  1. Han Y, Wu Y, Shen M, Huang X, Zhu J, Zhang X. Preparation and properties of polystyrene nanocomposites with graphite oxide and graphene as flame retardants. J Mater Sci 48:4214.
  2. Hofmann D, Wartig K-A, Thomann R, Dittrich B, Schartel B, Mu¨lhaupt R. Functionalized graphene and carbon materials as additives for melt-extruded flame retardant polypropylene. Macromol Mater Eng 298:1322.
  3. Dittrich B, Wartig K-A, Hofmann D, Mu¨lhaupt R, Schartel B. Flame retardancy through carbon nanomaterials: carbon black, multiwall nanotubes, expanded graphite, multi-layer graphene and graphene in polypropylene. Polym Degrad Stab 98:1495.

Graphene oxide as an additive in concrete: innovation in construction

Posted on | by Energeia Graphenemex

Graphene oxide as an additive in concrete:

innovation in construction

Mexico City – 9 years after being established, Energeia Fusion S.A. de C.V., the most important Mexican company in Latin America and promoter of the renowned Graphenemex® brand, launches the Graphenergy construction line, a new generation of nanotechnological additives for concrete with graphene oxide, which promises to strengthen the infrastructure and construction industry .

El Grafeno, también conocido como “el material del futuro”, finalmente traspasó la barrera de los laboratorios de investigación y se ha convertido en una realidad como potencial solución de innumerables necesidades sociales, ambientales e industriales. Este maravilloso nanomaterial consiste láminas atómicas de carbono extraídas del grafito y, gracias a sus interesantes propiedades mecánicas, eléctricas, térmicas, ópticas, etc., durante los últimos años se han invertido millones de dólares alrededor del mundo para tenerlo disponible en distintas aplicaciones, dentro de las cuales, la industria de la infraestructura y construcción ha logrado ser una de las más favorecidas.

Graphene career in the construction industry

2004 – Isolation of Graphene.

2010 – Recognition of the scientists Konstantin Novoselov and Andre Geim with the Nobel Prize in Physics for the isolation of Graphene.

2013 – Energeia Graphenemex is established, the first company in Latin America specialized in the production of graphene materials and development of applications.

2018 – Graphenemex® launches Nanocreto® on the market, the first additive for concrete with graphene oxide in the world (Mexico).

2019 – Graphenenano launches Smart additives, additives with graphene for concrete (Spain).

2019 – GrapheneCA presents its line of OG concrete admix products for the industry

concrete (USA).

2021- Scientists from the University of Manchester develop the concrete admixture Concretene (England).

2022 – Energeia – Graphenemex® launches the Graphenergy Construction line, a

improved version of its concrete admixture (Mexico).

Graphenergy construction is a water-based admixture compatible with other admixtures, designed to improve the quality of concrete or concrete, with the aim of reinforcing the pre-existing characteristics of concrete, such as mechanical resistance, but also to add value by providing non-existent properties in the original design, such as waterproofing, thermal insulation and antimicrobial protection.

How does Graphenergy construction work?

1. High impermeability and anti-corrosiveness

Graphenergy construction within the cementitious matrix forms molecularly more ordered and closed architectures that reduce the porosity of the structure and therefore create hydrophobic surfaces that, at a microstructural level, also hinder the passage of liquids and gases, hindering the passage of the agents that cause structural deterioration, especially in aggressive environments such as coastal or highly polluted environments.

Structure closure at the molecular level has also been demonstrated by electrical diffusivity measurements; These results support the protection of the metal structure of the concrete, increasing the useful life of the structure.

2. Improved mechanical properties

The more compact and organized architecture at the molecular level that Graphenergy Construction Graphene Oxide achieves within the concrete, allows microcrack limitation centers to form and therefore the structure becomes stronger when subjected to compression or tension loads, while favoring its flexibility.

3. Thermal insulation

The thermal insulation offered by Graphenergy construction is due to the ability of graphene oxide to dissipate heat with great efficiency and even to withstand intense electrical currents without heating up.

4. Antimicrobial protection

Graphenic additives offer different fronts of chemical and physical attacks of combined interaction, highly resistant to the formation of microbial biofilms, this means that microorganisms do not find a suitable environment to grow and release their by-products (eg. sulfuric acid) and, therefore, is not generated or, failing that, delays the appearance of microbiologically induced corrosion of concrete (MIC). This protection is extremely important, for example, for water systems since, inside the pipes, MIC is capable of dissolving up to 25 mm of concrete per year.

References

1. Basquiroto de Souza F., Proposed mechanism for the enhanced microstructure of graphene oxide–Portland cement composites. JOBE. 2022, 54, 104604

2. Dimov D., Ultrahigh Performance Nanoengineered Graphene Concrete Composites for Multifunctional Applications. Adv. Funct. Mother. 2018, 28, 1705183

3. Shamsaei E., Graphene-based nanosheets for stronger and more durable concrete: A review. Constr Build Mater. 2018, 183, 642

4. Krishnamurthy A., Superiority of Graphene over Polymer Coatings for Prevention of Microbially Induced Corrosion. 2015. Scientific Reports, 5:13858

5. https://blog.ferrovial.com/es/2022/04/graphene-sustainability-construction/

6. https://www.graphenano.com/graphene-arrives-in-construction-to-increase-the-resistance-of-concrete/

7. https://www.manchester.ac.uk/

8. https://www.cdt.cl/desarrollan-concrete-with-nanoparticles-of-graphene-to-repel-water-and-cracks/