Category: Graphene Oxide

Tapping into Graphene’s Potential:

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Tapping into Graphene’s Potential:

Enhancing Coatings with Nanotechnology for Weather Resistance

Coatings are designed for decorative purposes and to protect surfaces, especially against corrosion and moisture. In a coating system (multilayer), the top or finishing layer plays a crucial role as it must provide a good appearance and protect the inner layers and the substrate against environmental factors such as sunlight, humidity, corrosion, chemical resistance, soiling, etc., throughout its lifespan.

Today, Polyurethane (PU) is considered one of the coatings with the best physical-chemical characteristics for finishing coating applications and for its weather resistance. However, its weather resistance decreases with exposure to ultraviolet light over long periods.

Sunlight is one of the main causes of damage to coatings. Damage ranges from loss of physical properties, powdering (chalking), cracking, peeling, discoloration, and color change, because of chemical photodegradation, migration, evaporation, and interaction of other components with the coating.

In recent years, various nanostructured materials such as titanium, zinc oxide, cerium, and iron oxide have been implemented to improve the weather resistance of polymeric coatings. The mechanism is based on their projection effect (both absorption and dispersion) of incident rays in the UV region. These materials can stabilize coatings against exterior exposure, possess photocatalytic activity that can destroy the organic binder material present in coatings, leading to modifying the surface of these nanostructured materials to eliminate or inhibit their photocatalytic activity, requiring more processes, time, and money.

Recently, graphene has attracted much attention as a new additive and material for producing coatings to enhance anticorrosive, antimicrobial, and weather-resistant properties, due to its special electronic structure that provides unique electrical, mechanical, and chemical properties. Graphene is a nanomaterial formed by one or more layers of carbon (formed by carbon atoms bonded hexagonally with a thickness of one carbon atom). This structure enables graphene-based materials to absorb photons in the UV region. This UV absorption capacity, as well as the absence of photocatalytic activity of graphene materials, allows introducing these materials as new additives for the photo-stabilization of polymeric coatings, i.e., with greater resistance to UV radiation

Currently, Energeia – Graphenemex®, is in constant development of nanotechnological coatings with better properties. Studies have been conducted on the influence of graphene oxide on the weathering behavior of PU coatings. To evaluate the performance of graphene oxide, a PU coating with graphene oxide (PU/GO) was compared with a PU coating containing a commercial organic UV absorber (PU/control).

Color change in a coating during exposure to weathering (sunlight) is the most important and rapid parameter to visually evaluate coating degradation. To evaluate, color change, samples coated with Polyurethane with and without graphene material were introduced into an accelerated weathering chamber (based on ASTM G154). According to the standard, a QUV weathering chamber model QUV/se was used to accelerate weathering conditions. Coated samples were cyclically exposed to UVA radiation (energy 0.89 W/m2) for 8 hours, followed by moisture condensation for 4 hours at 50 °C. The color of the coatings was evaluated before exposure to compare their initial color, and subsequently evaluated at different exposure times, this evaluation was performed until reaching an exposure time of 1200 hours.

The main component of color typically considered in weathering behavior is the total color change or Delta E (ΔE). Fig. 1 shows the ΔE, as the most comprehensive criterion of color changes, which is the sum of changes in all color components.

As can be seen, most of the color variations throughout the exposure time belong to the PU/control coating. The sample containing graphene oxide (PU/GO) at 251 hours of exposure time shows a lower color change compared to PU/control. With the increase in exposure time in the weathering chamber, color variations can be observed, but the sample with graphene oxide continues to show lower color changes, indicating that the incorporation of GO in Polyurethane provides more resistance and maintains its stability for longer exposure times to weathering.

Fig 1. Total color change (ΔE) versus exposure time for Polyurethane coatings with graphene oxide (PU/GO) and without graphene oxide (PU/control) during accelerated weathering test.

From a physical point of view, graphene oxide (GO) has higher transmittance in the visible region compared to graphene, which is more favorable for its use as a UV protector in finishing coatings. On the other hand, thanks to the high surface area of graphene materials, they can also provide excellent barrier effect properties and thus develop anticorrosive coatings with greater weather resistance.

Energeia – Graphenemex®, through its Graphenergy line, offers a wide range of nanotechnological coatings with graphene. These coatings offer high anticorrosive and antimicrobial protection. In addition to providing high wear resistance, UV resistance, impermeability, and extraordinary adhesion, with the aim of improving the life of any surface or installation and reducing maintenance costs.

References

  1. G. Wang, X. Shen, B. Wang, J. Yao, J. Park, Synthesis and characterisation of hydrophilic and organophilic graphene nanosheets, Carbon N. Y. 47 (no. 5) (2009) 1359–1364.
  2. B. Ramezanzadeh, M. Mohseni, H. Yari, S. Sabbaghian, A study of thermal-mechanical properties of an automotive coating exposed to natural and simulated bird droppings, J. Therm. Anal. Calorim. 102 (no. 1) (2010).
  3. N. Rajagopalan, A.S. Khanna, Effect of Methyltrimethoxy Silane Modification on Yellowing of Epoxy Coating on UV (B) Exposure vol. 2014, (2014).
  4. M. Hasani, M. Mahdavian, H. Yari⁎, B. Ramezanzadeh. Versatile protection of exterior coatings by the aid of graphene oxide nanosheets; comparison with conventional UV absorbers. 2017.
  5. S.M. Mirabedini, M. Sabzi, J. Zohuriaan-Mehr, M. Atai, M. Behzadnasab,
  6. Weathering performance of the polyurethane nanocomposite coatings containing silane treated TiO2 nanoparticles, Appl. Surf. Sci. 257 (no. 9) (2011) 4196–4203.
  7. N.S. Allen, M. Edge, A. Ortega, C.M. Liauw, J. Stratton, R.B. McIntyre, Behaviour of nanoparticle (ultrafine) titanium dioxide pigments and stabilisers on the photooxidative stability of water based acrylic and isocyanate based acrylic coatings, Polym. Degrad. Stab. 78 (no. 3) (2002) 467–478.
  8. Effect of Silane Modified Nano ZnO on UV Degradation of Polyurethane Coatings. vol. 79, (2015), pp. 68–74.
  9. M. Rashvand, Z. Ranjbar, S. Rastegar, Nano zinc oxide as a UV-stabilizer for aromatic polyurethane coatings, Prog. Org. Coatings 71 (4) (Aug. 2011) 362–368.

Defying the flames

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Defying the flames:

The triumph of graphene oxide in the creation of fire-fighting coatings

The inclusion of Graphene Oxide (GO) in coatings demonstrates effectiveness in inhibiting flammability, providing a fire-resistant barrier. Benefits include anti-corrosion protection, antimicrobial properties and increased adhesion to substrates. This advance highlights Energeia-Graphenemex’s innovation in the production of fireproof coatings, positioning itself as a leader in the research and application of high-quality graphene materials.

Coatings are used in various sectors, at an industrial level the use of coatings are focused on protection against corrosion, while at a commercial level they are used for infrastructure maintenance and for decorative purposes. Today, the coatings industry continues to constantly research the development of improved coatings, with antimicrobial, non-stick properties, and greater resistance to chemical attack and weathering. However, at a commercial level there are few developments focused on fireproof coatings (flame retardant) for fire protection in infrastructure.

Traditional fireproof coatings are cementitious coatings, based on Portland cement, magnesium oxychloride cement, vermiculite, gypsum and other minerals. In addition, they contain fibrous fillers, binders, supplements and additives that control density and rheology, these materials are generally mixed with water on site and applied by spraying some construction or can be applied to a flammable substrate by using a roller, in thicknesses of half an inch or more. However, due to their weight, thickness and poor aesthetics, they limit architectural design.

In coatings and paint industry, there is a wide variety of coatings based on different types of resins (polymers) and additives. Due to their nature, most of these coatings are flammable and combustible materials. That is, they are materials that can catch fire when exposed to fire, suffering degradation and the release of heat to subsequently initiate the spread of the flame, releasing smoke and toxic gases, being a danger to the safety of human life and property. On the other hand, polymer-based fireproof coatings use conventional additives based on halogens (bromine and chlorine), as well as phosphorus, melamine and inorganic compounds, to improve the fire resistance of the coatings, however, these materials are toxic to humans and the environment.

In recent years, Energeia-Graphenemex has focused on the production of graphene materials. Graphene is the most revolutionary nanotechnological additive for the coatings and paints industry, as it allows the development of coatings with extraordinary anti-corrosion protection, coatings with antimicrobial properties, coatings with better adhesion to substrates and greater resistance to UV radiation. In this sense, graphene oxide (GO) has been shown to be a new additive that helps inhibit or reduce the flammability of coatings, to produce effective fireproof coatings.

Its efficiency is associated with the fact that GO has a strong barrier effect, high thermal stability and great surface absorption capacity that are favorable for effectively reducing heat and mass transfer.

The incorporation of GO in coatings can improve flame resistance, by inhibiting the two key terms: heat and fuel. That is, it can function as a flame retardant in the following ways:

• GO possesses a unique two-dimensional layer structure and can promote the formation of a dense continuous layer of carbon during the combustion process (see Fig. 1). Carbon can act as a physical barrier to prevent heat transfer from the heat source and delay the escape of products (pyrolysis) from the coating.

• Because GO has a large surface area, it can effectively adsorb flammable volatile organic compounds or hinder their release and diffusion during combustion.

• The presence of oxygenated groups in the GO structure means that, during the combustion of the coating, the oxygen-containing groups in GO can undergo decomposition and dehydration at low temperature, thus absorbing heat and cooling the polymeric substrate during combustion. Meanwhile, gases generated by dehydration can dilute the oxygen concentration around the ignition periphery, decreasing the risk of fire spread.

In summary, the incorporation of GO in coatings can provide fire protection, because they can release water and provide thermal insulation effects.

Graphene-based flame-retardant coatings are designed to retard ignition and burn rate, and must provide a fire-resistant barrier.

Energeia – Graphenemex®, Mexican company, leader in Latin America in research and production of graphene materials for the development of industrial applications. It has extensive experience in the large-scale production of graphene oxide (GO) and has high-quality graphene materials for sale for use in different industries.

Fig.1 Flame retardancy test of coatings (Method based on UL-94 classification), where;
a) coating without GO and b) Coating with GO.

References

  1. Sachin Sharma Ashok Kumar, Shahid Bashir, K. Ramesh, S. Ramesh, Progress in Organic Coatings, 154, (2021)
  2. Weil, Edward. D. Fire-Protective and Flame-Retardant Coatings – A State-of-the-Art Review. Journal of Fire Sciences, 29(3), 259–296.
  3. Lipiäinen, H., Chen, Q., Larismaa, J., & Hannula, S. P. (2016). The Effect of Fire Retardants on the Fire Resistance of Unsaturated Polyester Resin Coating. Key Engineering Materials, 674, 277–282.
  4. Md Julker Nine, Dusan Losic. Mahmood Aliofkhazraei, Nasar Ali, Mircea Chipara, Nadhira Bensaada Laidani, Jeff Th.M. De Hosson, Handbook of Modern Coating Technologies, Elsevier, 2021, Pages 453-492.

Reinforced Concrete

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Reinforced Concrete:

Why Choose Fibers with Graphene Oxide?

Fiber reinforced concrete is an improved version of conventional concrete characterized by better performance against cracking, deformation, fatigue and impact. It is widely used for the manufacture of industrial and commercial floors, tunnels, slopes, tanks, shotcrete, prefabricated and in some cases as a replacement for the electrowelded mesh of floors, but not as a substitute for the reinforcing steel of structural columns, load-bearing walls. or suspended beams. Unlike concrete reinforced with steel structures, fibers represent a discontinuous and homogeneous three-dimensional reinforcement within the concrete mixture that allows it to have the same characteristics at each point of the structure.

Of the extensive classification of fibers in terms of materials, lengths, thicknesses and geometries, the main competition is between steel fibers and polypropylene fibers, because both materials increase the toughness of concrete and allow it to continue absorbing loads before collapse. The difference is that steel fibers control cracking during the setting of the concrete and after hardening, they have great tensile strength and do not deform, but rather absorb energy and transform it into an internal stress; characteristics that make them very useful for use in concrete exposed to high loads. Polypropylene fibers contribute to the control of cracks due to plastic contraction, external loads, temperature, or drying contraction and, although its tensile strength is lower than steel, its deformation capacity allows it to absorb large loads without failing. They are less expensive, easier to handle and are generally indicated for lower load concretes.

Although the mechanical properties of steel fibers are superior to those of polypropylene and subject to the characteristics of the project and the applicable regulations, there are other technical differences that are worth considering when selecting:

Durability- The steel fibers within the concrete usually remain stable and isolated from the external environment, however, when this insulation is broken either by capillarity, microcracking or by a change in the pH of the concrete, the fibers become susceptible to corrosion, whose oxidation in the future will be responsible for the loss of adhesion with the concrete. The advantage of polypropylene fibers is that they are suitable for placement in humid and marine environments thanks to their chemical stability, resistance to corrosion and degradation.

Volumetric weight- The amount of polypropylene fibers per kilogram of weight is greater than those contained in one kilogram of steel fibers. This means that, to have a similar distribution, approximately between 5 and 8 kg of metallic fibers should be dosed for each kilogram of polypropylene fibers and, although the volumetric weight can be considered irrelevant for performance, the cost and handling of the product can be two interesting variables.

Adhesion – The adhesion or interfacial bond between the fiber and the concrete is essential for the long-term success of the structure and is quantified as the force necessary for the fiber to be torn from the concrete matrix or undergo rupture. In steel fibers, their adhesion depends mainly on their morphology and length; however, polypropylene fibers, in addition to facilitating the manufacture of different configurations, can also be chemically modified to improve their adhesion.

Distribution- Depending on the quantity dosed, steel fibers can form “hedgehogs” or leave spikes on surfaces, posing risks during handling and after placement. A disadvantage of polypropylene fibers is their hydrophobicity or incompatibility with water, this means that when the mechanical mixing of the fibers is carried out within the concrete composed of water, cement and aggregates, they can agglomerate and cause clumps, especially at dosages. elevated; Consequently, poor distribution, aggregation or formation of air spaces within the concrete will have a negative impact on its adhesion and, therefore, its performance.

Fire resistance – In the event of a fire, concrete can exhibit explosive detachment or “spalling” behavior, which consists of the violent expulsion of fragments due to the increase in pressure exerted by the release of water vapor until detachment occurs when the pressure exceeds the tensile strength of the concrete. Polypropylene microfibers melt at temperatures between 160 and 170° C, therefore creating interconnected channels that increase the permeability of the concrete and help release moisture and internal pressure.

The Mexican company Energeia-Graphenemex®, through its Graphenergy Construction division, takes advantage of the benefits of graphene nanotechnology to improve the characteristics of conventional polypropylene fibers; Its specialized formula allows obtaining individual filaments with greater mechanical and thermal resistance, better distribution and greater adhesion within the concrete compared to common fibers.

How does graphene oxide improve the performance of polymer fibers?

Graphene oxide is one of the most interesting materials to improve the characteristics of many polymers. It consists of sheets of graphene or pure carbon stabilized with oxygenated groups that make it a multifaceted structure, compatible with water, like cement crystals and easily combinable with other compounds to design materials with new or improved properties, for example:

Distribution within the concrete mix
One of the advantages of graphene oxide designed for the manufacture of polypropylene fibers is its surface chemistry consisting mainly of oxygenated groups (OH- and COOH-) that help maintain the affinity of the fibers with the aqueous elements of the graphene paste. cement acting in a similar way to plasticizing additives, this is because graphene oxide reduces the surface energy of the fibers, facilitating their distribution within the mixture and avoiding aggregates.

Adherence
Another benefit of graphene oxide present in polypropylene fibers is the electrostatic repulsion that it generates between the cement particles; This phenomenon prevents cement agglomeration and increases the degree of fiber-cement interaction by altering the hydration products and increasing their degree of polymerization. In hardened concrete, this effect increases the coefficient of friction so that when a crack displaces a fiber, more load will be required to displace it within the concrete.

Mechanical strength
Graphene oxide increases the tensile and breaking strength of polymers, this is because its elastic modulus (230 GPa) is slightly higher than that of steel and its alloys (190-214 GPa), but comparable to of Zirconia (160-241 GPa) and Cobalt alloys (200-248 GPa), therefore, fibers with graphene oxide have a lower risk of fracture and are more durable than common fibers

Degradation resistance
Polymeric fibers with graphene oxide have a longer useful life because it is a material that differs from many others that deteriorate because of UV radiation, graphene oxide maintains its structural integrity and mechanical properties, in addition, it is chemically inert. and more resistant to corrosive media.

Thermal stability
Graphene oxide increases the thermal stability of polypropylene by forming interconnected bridges or pathways throughout the polymer matrix, improving heat transport.

Drafting: EF/DH

Sources

  1. Fabrication of graphene oxide/fiber reinforced polymer cement mortar with remarkable repair and bonding properties.             J. Mater. Res. Technol. 2023; 24: 9413;
  2. The incorporation of graphene to enhance mechanical properties of polypropylene self-reinforced polymer composites J. Wang et al. / Materials and Design 195 (2020) 109073;
  3. Simultaneous enhancement on thermal and mechanical properties of polypropylene composites filled with graphite platelets and graphene sheets. Composites Part A 112 (2018);
  4. Experimental study on the properties improvement of hybrid Graphene oxide fiber-reinforced composite concrete. Diamond & Related Materials 124 (2022) 108883.
  5. Upcycling waste mask PP microfibers in portland cement paste: Surface treatment by graphene oxide. Materials Letters 318 (2022) 132238;
  6. An Experimental Study on the Effect of Nanomaterials and Fibers on the Mechanical Properties of Polymer Composites. Buildings 2022, 12,
  7. State-of-the-Art Review of Capabilities and Limitations of Polymer and Glass Fibers Used for Fiber-Reinforced Concrete. Materials 2021, 14, 409;
  8. Mecanismos de desprendimiento explosivo del hormigón bajo fuego y el efecto de las fibras de polipropileno. Estado del conocimiento. Asociación argentina de tecnología del hormigón. Revista Hormigón 62 (2022-2023) 25

Polymeric Graphene Oxide Fibers

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Polymeric Graphene Oxide Fibers:

an effective solution to prevent cracking in Concrete

Globally, concrete is the most used construction material. Concrete is applied in different infrastructures, including buildings, bridges, dams and tunnels, due to its high compressive strength. However, concrete has some limitations and problems, such as low tensile strength and cracking. Cracks or fissures can appear during the production of concrete and at subsequent stages. They begin as nanoscale cracks, later they join together forming micro and macro cracks. This behavior is closely associated with the hydration process that cement undergoes, where it releases heat and increases the temperature of the concrete. In large structures, heat cannot be released easily, causing expansion stresses, and thermal contraction, leading to cracking.

Because concrete is constantly exposed to impact, fatigue and other types of loads, cracks or fissures, and irreparable failures can occur, it is why it is common to reinforce it with polymer fibers to improve the physical-mechanical characteristics of concrete.

Incorporating fibers into concrete has proven to be effective in delaying or preventing crack propagation. At a commercial level, there is a wide range of polymeric fibers as three-dimensional secondary reinforcement of concrete and mortar, with different lengths and sizes (macrofibers and microfibers). These polymer fibers are made from materials such as polypropylene (PP), high-density polyethylene (HDPE), PVA and polyester.

However, there are some disadvantages or limitations of commercial polymer fibers, the hydrophobic nature of polymer fibers, or/and its elastic modulus is insufficient, so the incorporation of polymer fibers in concrete only slightly improves the resistance to the tension. Furthermore, the little improvement in tensile strength is mainly attributed to insufficient bond strength at the interface between the fiber and matrix, i.e., low compatibility (no adequate anchorage) of the fiber with the concrete. So the fibers easily detach from the concrete, increasing the risk of cracking and failure in the concrete. (See Figure 1)

Figure 1. Differences between commercial polymer fibers (a) and metallic fibers (b) in concrete.

Currently Energeia Fusión- Graphenemex, under its Graphenergy Construction line, developed polymeric macrofibers with graphene oxide (GO). Graphene oxide is a nanomaterial, which due to its unique physical and chemical characteristics, such as its large surface area (736.6 m2/g), extraordinary mechanical properties (25 GPa), thermal properties and its unique structure with multiple oxygen-containing groups on its surface, makes GO an ideal material for modifying the surface of polymer fibers. These characteristics allow improving the interface or compatibility of the fibers with cementitious materials and/or concrete.

The oxygenated groups of GO act as anchoring sites for the formation of cement hydration products, improving the interface between the fibers and the cementitious matrix (See Figure 2). Consequently, a stronger interface leads to an improvement in the tensile strength of the concrete.

Figure 2. Scanning Electron Microcopy (SEM) analysis of fibers torn from concrete. PVA fiber (a and b).
PVA/GO fiber (e and f). Taken from [Ref. 2]

When a concrete structure is subjected to loading, tension and compression stresses begin to build up. Over time, small cracks appear in places where the stress reaches a critical point. In this sense, the Graphenergy reinforcing fibers remain solidly anchored in the concrete matrix and absorb the tensile stress at any point and direction.

If there is a small crack the fibers are held firmly within the concrete, as the tension increases the fiber slowly elongates (deforms) until it reaches its maximum strength. With a 38% improvement in tensile strength and 29% more elongation than commercial reinforcement, concrete structures reinforced with Graphenergy fibers can withstand high bending stress over a long period. These nanotechnology fibers delay the appearance of the first crack and slow down the spread of cracks in the concrete.

The main difference between Graphenergy reinforcing fibers and other commercial fibers is that fibers with graphene become part of the concrete matrix and give rise to a composite material. Graphenergy reinforcing fibers form a reinforcing network throughout the structure, reducing or inhibiting the appearance of cracks (effective crack control), and improve the ductility of concrete. Additionally, Graphenergy reinforcing fibers improve concrete quality, providing greater shrinkage resistance, fire resistance and greater impermeability in concrete.

References

  1. Filho, A., Parveen, S., Rana, S., Vanderlei, R., & Fangueiro, R. (2020). Mechanical and micro-structural investigation of multi-scale cementitious composites developed using sisal fibres and microcrystalline cellulose. Industrial Crops and Products, 158, 112912.
  2. Yao, X., Shamsaei, E., Chen, S., Zhang, Q. H., de Souza, F. B., Sagoe-Crentsil, K., & Duan, W. (2019). Graphene oxide-coated Poly(vinyl alcohol) fibers for enhanced fiber-reinforced cementitious composites. Composites Part B: Engineering, 107010.
  3. Lingbo Yu, Shuai Bai, Xinchun Guan, Effect of multi-scale reinforcement on fracture property of ultra-high performance concrete, Construction and Building Materials, Volume 397, 2023, 132383, ISSN 0950-0618.
  4. Chen Lin, Terje Kanstad, Stefan Jacobsen, Guomin Ji, Bonding property between fiber and cementitious matrix: A critical review, Construction and Building Materials, Volume 378, 2023, 131169, ISSN 0950-0618.
  5. Bolat, H., Şimşek, O., Çullu, M., Durmuş, G., & Can, Ö. (2014). The effects of macro synthetic fiber reinforcement use on physical and mechanical properties of concrete. Composites Part B: Engineering, 61, 191–198. 

Graphene Oxide, the nanomaterial that will reduce the impact of corrosion

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Graphene Oxide

the nanomaterial that will reduce the impact of corrosion

What is corrosion?

The term corrosion refers to the destruction of a material because of its chemical or electrochemical interactions with the surrounding medium. The importance of its prevention and/or control is due to the fact that, being a natural phenomenon, once started it is practically impossible to stop. Therefore, an uncontrolled evolution will invariably compromise the integrity and useful life of the materials, generating the industry involved direct and indirect expenses due to loss of product, stoppage of activities due to maintenance until the replacement of machinery or structures.

“Economic losses caused by corrosion exceed 3.4% of global GDP”

Microbiologically influenced corrosion

Microbiologically influenced corrosion (MIC) can be defined as the electrochemical process in which microorganisms such as algae, fungi and bacteria initiate, facilitate, or accelerate a corrosion reaction, generally located in the form of cracks. or pitting on both metal and concrete surfaces. Although corrosion involves various variables, it is estimated that MIC participates in 20 to 40% of all corrosion failures, particularly in hydraulic and oil infrastructure, with costs close to 2 billion dollars annually.

Why do you start the MIC?

The presence of humidity in any environment is the ideal habitat for the growth of numerous communities of microorganisms that, combined with optimal conditions of temperature, pH, nutrient flow, etc., promotes their adhesion and growth on surfaces, forming a biofilm that is not removed, it grows into a hardened, obstructive biomass within which sulfate-reducing bacteria, acid-producing bacteria, iron-reducing bacteria, and gel-forming bacteria promote corrosion or MIC through destructive electrochemical reactions of the surfaces.

How do you combat it?

There are three most common methods to try to combat MIC, the first is mechanical cleaning of surfaces to remove biofilms, ideally in incipient stages, however, it is not always possible to access all exposed areas, making their efficiency difficult. The second is the use of biocidal agents that, in addition to being expensive, most may not be friendly to human health and the environment. Finally, and perhaps the most suitable method is the placement of external barriers in the form of coatings or polymeric films to prevent direct contact of the metal or concrete structures with the aggressive medium.

Corrosion control in concrete

The options available to protect concrete against corrosion from its fresh state are the additions of pozzolanic materials, fly ash, blast furnace slag, sulfate-free aggregates, polymer fibers, use of sulfate-resistant cement or modified with nanoparticles such as nanotubes and carbon nanofibers, silica nanoparticles, alumina or titanium dioxide. For protection in the hardened state, it is common to apply physical barriers such as anti-corrosion coatings or polymeric films and, for the protection of metal structures, in addition to anti-corrosion coatings, you can use galvanized, tinned structures or the placement of magnesium sacrificial anodes. However, it is considered that, due to the natural porosity of concrete, there are no totally efficient methods that attack the problem of corrosion towards the interior of structures.

Corrosion in concrete can occur due to carbonation, ingress of chlorides and sulfates or due to microbiological attack. When the concrete has reinforcing steel and is attacked by corrosion, oxide can grow 2 to 4 times the volume of the original steel, causing loss of adhesion of concrete and put the resistance of the material at risk. Furthermore, the porosity of the concrete, in addition to allowing the passage of moisture for the entry of aggressive ions, also offers millions of ideal niches for the retention of microorganisms and for the subsequent formation of MIC-initiating biofilms, not only because they favor their anchoring, but because they make their removal difficult and promote the advancement of corrosion.

“It is expected that by 2032 the corrosion inhibitors market will amount to 12.5 billion, and in 2022 this figure will be around 8.3 billion.”

Graphene and graphene oxide are multifunctional carbon nanomaterials with extraordinary properties that, when incorporated as a nanofiller in other compounds such as coatings, plastics or cement, have the ability to molecularly organize their structure in such a way that they improve their resistance to chemical, physical and microbiological attacks. Among their particularities is that they are inert nanostructures, that is, they are stable, they do not react with other materials and they do not suffer oxidation or corrosion. They are extremely thin and light, but at the same time, very resistant and flexible. They are impermeable even to gases and have highly efficient antimicrobial mechanisms.

Below is a summary of some of the most notable research on the use of graphene as an alternative against microbiologically influenced corrosion (MIC):

2015- The Department of Materials Science and Engineering at Rensselaer Polytechnic Institute, New York, USA, modified polyurethane coatings with graphene identifying 10 times greater protection against MIC compared to unmodified polyurethane coatings.

2017- The Nanobiomaterials laboratory of the Federico Santa María Technical University, Valparaíso, Chile, evaluated the direct effect of graphene placed on nickel substrates and its interaction with bacteria that cause corrosion. The results showed an impermeable barrier generated by graphene that blocked the interaction between bacteria and the metal, but without a bactericidal effect.

2021- The Department of Civil and Environmental Engineering, South Dakota School of Mines and Technology, USA, reported that multiple layers of graphene restricted MIC attack on copper and nickel surfaces 10 times more.

2021– The School of Engineering at the University of Glasgow, Scotland, examined the deterioration of graphene oxide (GO)-modified cement pastes exposed to acidic environments. The results demonstrated that the presence of GO reduces the loss of mass in the concrete due to these attacks, recognizing it as a potential additive to modify the microstructure and useful life of concrete in the face of aggressive environments such as those present in chemical product warehouses to systems. of wastewater.

Energeia Fusion (Graphenemex®), the leading Mexican company in Latin America in the production of graphene materials, after a long journey of research, in 2018 launched the Graphenergy Line on the market, which includes a series of anticorrosive and antimicrobial coatings with graphene nanotechnology and the first additive for concrete with graphene oxide in the world, whose individual or combined use promises great benefits against corrosion.

Graphenergy Construction is a water-based additive with graphene oxide designed to improve the quality of cement structures in terms of mechanical resistance and durability. The added value that graphene oxide offers to concrete in the fight against MIC from the outside to the inside is the result of a series of events that begin by favoring the hydration of the cement, acting as water reservoirs and as a platform for the growth of crystals. of C-S-H and to dissipate the heat of hydration; improves the interfacial transition zones between the cement paste and the aggregates, helping to reduce the size and volume of the pores, this in turn favors an increase in mechanical resistance, reduces permeability, increases its resistivity, that is, reduces the transfer of electrical charges into the interior of the concrete, delaying the onset of corrosion and, finally, modifying the electrostatic charges and the wettability of the surfaces, making the formation of biofilms that cause MIC difficult.

Graphenergy coatings formulated with graphene oxide offer great resistance against corrosion in coastal and non-coastal areas, as well as excellent antimicrobial protection without biocidal mechanisms, since their effect consists of preventing the adhesion of microorganisms to surfaces. In addition, its impermeability, resistance to abrasion and resistance against the intense effects of the elements increase its useful life and, therefore, substantially reduce the maintenance costs of both metal and concrete structures.

Drafting:  EF/DH

References

  1. The Many Faces of Graphene as Protection Barrier. Performance under Microbial Corrosion and Ni Allergy Conditions. Materials 2017, 10, 1406;
  2. Effect of graphene oxide on the deterioration of cement pastes exposed to citric and sulfuric acids. Cement and Concrete Composites, 2021, 124, 104252;
  3. Superiority of Graphene over Polymer Coatings for Prevention of Microbially Induced Corrosion. Scientific Reports, 2015, 5:13858;
  4. Atomic Layers of Graphene for Microbial Corrosion PreventionACS Nano 2021, 15, 1, 447;
  5. Microbiologically induced corrosion of concrete in sewer structures: A review of the mechanisms and phenomena. Construction and Building Materials. 2020, 239, 117813;
  6. Microbiologically Induced Corrosion of Concrete and Protective Coatings in Gravity Sewers. Chinese Journal of Chemical Engineering, 2012, 20(3) 433;
  7. In situ Linkage of Fungal and Bacterial Proliferation to Microbiologically Influenced Corrosion in B20 Biodiesel Storage Tanks. Front. Microbiol. 2020, 11;
  8. Chapter 1 – Failure of the metallic structures due to microbiologically induced corrosion and the techniques for protection. Handbook of Materials Failure Analysis. With Case Studies from the Construction Industries. 2018, 1;
  9. Maleic anhydride-functionalized graphene nanofillers render epoxy coatings highly resistant to corrosion and microbial attack. Carbon, 2020, 159, 586;
  10. Gerhardus Koch, Cost of corrosion, In Woodhead Publishing Series in Energy, Trends in Oil and Gas Corrosion Research and Technologies, Woodhead Publishing, 2017;
  11. https://www.futuremarketinsights.com/reports/corrosion-inhibitors-market.
  12. http://www.imcyc.com/revistacyt/oct11/artingenieria.html

Innovation in the construction industry

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Innovation in the construction industry:

graphene oxide as an adjuvant to improve the resistance and durability of pavement

Concrete, due to its production efficiency, abundant sources of raw material, workability, and versatility, is a widely used material in the construction industry; among its numerous applications are rigid pavements for highways, airports, industrial floors and bridges, however, and despite its excellent resistance to compression, concrete presents limitations such as low tensile and flexural resistance that, together with factors such as overloads or environmental conditions, it usually develops failures such as cracking, perforations, detachment or erosion that will invariably require repair. Therefore, improving its quality, in addition to increasing its useful life and reducing risks, also allows maintenance work to be reduced or spaced out and, consequently, avoids the stoppage of operations or road closures, in turn representing significant economic savings.

In addition to quality and economy, another of the objectives of the construction industry is to reduce the carbon footprint, taking as a reference that the main concrete binder is cement and that, for each ton of cement manufactured, 1 ton of carbon is released. CO2 into the atmosphere. That is why there is a constant search for technologies and/or materials that improve or equalize the performance of concrete, in principle using a lower cement content through the use of cement substitutes such as mineral microparticles, an industrial waste product for example: fly ash, blast furnace slag or silica fume; reinforcements with steel, synthetic or glass fibers; resins and recycled materials such as tire rubber, polypropylene, PET or recycled concrete itself, as well as a wide variety of lignosulfonate, naphthalene sulfonate, melamine or polycarboxylate-based additives to provide plasticizing, water-reducing, setting accelerator or retardant functions, among other.

A valuable tool to add value in the triad: quality, economy and the environment, is nanotechnology, based on the premise that cement is mostly made up of C-S-H nanocrystals, responsible for the cohesive properties, hardening and, in definitively, of its mechanical resistance. This means that manipulating and modifying the structure of the cement from its nano level brings benefits at the macro level, that is, in the concrete as a finished product.

Throughout the last ten years of research and application of nanotechnology in construction, Graphene Oxide (GO) appeared on the scene, a carbon nanoparticle derived from graphite with excellent mechanical, thermal and barrier properties; Its good dispersion in water and great affinity for cement nanoparticles have shown interesting attributes to accelerate cement hydration, increase the production of C-S-H nanocrystals and reduce cement pores, which together represent important benefits in strength, durability and variety of infrastructure applications. Likewise, it has been shown that the manufacture of polymeric fibers for concrete modified with GO contributes to significantly improve its resistance to tension, impact, and abrasion, delays its deterioration due to corrosion or UV radiation and makes it more thermally stable, reduces cracking, among other benefits.

Derived from the great potential of this nanomaterial for the construction industry, in 2022 Sustainability magazine used the Web of Science (WoS) database to carry out an analysis of the research generated in the period 2010-2022 regarding the use of carbon dioxide. graphene in cement compounds. In this study, a total of 608 publications related to mechanical resistance, durability, thermal conductivity, among others, were identified, but only less than 10 journals made reference to the comprehensive benefits that GO offers to rigid pavements, either individually or as a three-dimensional reinforcement through the use of polymeric fibers, which represents a little explored application, but with large areas of opportunity.

Tomado de: Sustainability 2022, 14, 11282.

Energeia – Graphenemex®, the 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 Construction® product line in 2018, placed an additive on the market for the first time for concrete with graphene oxide that contributes to improve the microstructure of cement-based conglomerates from their initial stages. Subsequently, in 2020 and thanks to its extensive experience in handling nanocomposites, it developed a new generation of polymeric macrofibers with graphene nanofilling. The benefits that GO offers at the nano and micrometric level have been evaluated in the laboratory and in the field on concrete macro designs, obtaining excellent results in terms of workability, density, impermeability, heat dissipation, setting, appearance and with balanced mechanical contributions of resistance to compression, tension, flexibility and abrasion that together complement the economic, environmental and quality needs of rigid pavements, among many other cement-based structures. Its use is very simple and does not require additional equipment or processes to those regularly used in construction, in addition to allowing adjustments in its handling, dosage and use in conjunction with other additives to improve its performance.

Drafting: EF/DHS

References

  1. Houxuan Li, et al., Recent progress of cement-based materials modified by graphene and its derivatives. Materials 2023, 16, 3783. 2. I. Fonseka, et al., Producing sustainable rigid pavements with the addition of graphene oxide. 2023; 3. Byoung Hooi Cho., Concrete composites reinforced with graphene oxide nanoflake (GONF) and steel fiber for application in rigid pavement. Case Stud. Constr. Mater. 2022; 17: e01346; 4. Kiran K. Khot, Experimental study on rigid pavement by using nano concrete. Int Res J Eng Techno, 2021; 08: 07,4865; 5. Jayasooriya, D. et al., Application of graphene-based nanomaterials as a reinforcement to concrete pavements. Sustainability 2022, 14, 11282; 6. Sen Du, et al., Effect of admixing graphene oxide on abrasión resistance of ordinary portland cement concrete. AIP Advances. 2019; 9: 105110; 7. D. Mohottia, et al., Abrasion and Strength of high percentage Graphene Oxide (GO) Incorporated Concrete. J. Struct. Eng. 2022; 21: 1; 8. Fayyad, T., Abdalqader, A., & Sonebi, M. An insight into graphene as an additive for the use in concrete. In Civil Engineering Research Association of Ireland Conference 2022 (CERAI 2022): Proceedings (CERAI Proceedings).

Overcoming Construction Challenges

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Overcoming Construction Challenges:

Graphene Oxide Additives Minimize Thermal Cracking

In concrete, the binding agents are mainly a combination of pozzolanic materials and cement that, during the hydration process, releases heat accompanied by volumetric changes. This phenomenon in the presence of elements with low thermal dissipation prevents heat from diffusing efficiently, resulting in a temperature gradient between the outer surface and the inner core. That is, the temperature on the surface of the mixture usually cools faster, but inside it, the temperature rises gradually. This non-uniformity in heat distribution can generate large tensile stresses responsible for the well-known thermal cracking of concrete.

Current strategies to reduce such thermal stresses include placement of cooling pipes, use of low-heat Portland cement, phase change materials, polymeric fibers, or surface insulation. However, little attention is paid to improving the spread of heat in the cement itself. In this sense, and since cement is a nanostructured material due to the content of C-S-H nanoparticles, it is not uncommon for the nanoscale to be one of the most innovative trends in modern civil engineering, since it has been proven that most of the affectations of concrete, as thermal cracking, originate from different chemical and mechanical factors of the cement structure, the main concrete binder.

Graphene oxide (GO) is an oxidized version of Graphene, the nanomaterial that over the past decade has been the focus of numerous industries, including the construction industry. Both nanostructures are a single sheet of densely organized carbon atoms that provide numerous mechanical, thermal, and electrical properties, among others.

GO, unlike Graphene, contains a large number of oxygenated groups of the epoxide (C-O-C), hydroxyl (-OH) and carboxyl (-COOH) type that make it, on the one hand, a material that is easily dispersible in water and, on the other , give it the ability to interact with the C-S-H nanoparticles of the cement to transfer its properties and improve its performance and durability from the micro and nano scale.

Thermal conductivity

The thermal conductivity of GO depending on the degree of oxidation can reach 670 W/ (m K), while the conductivity of copper and aluminum is approximately 384 and 180 W/ (m K), respectively. This means that GO can conduct heat more efficiently than metals. However, transferring this property to other materials is not an easy task, for which it is important to overcome three main challenges:

i) Have extensive scientific knowledge of graphene materials, if possible, from their synthesis or production,

ii) Control the quality of the mix design and,

iii) Have a comprehensive vision, both technical and scientific, for the proper use and distribution of GO nanoparticles with cement to achieve the objectives set.

Graphenergy Construcción® is a water-based multipurpose additive with a specialized formula based on graphene oxide that favors the cement hydration process, not only acting as a promoter for the formation of a network of C-S-H crystals responsible for the densification and resistance of concrete, but also improves the thermal conductivity during its hydration and setting.

During the hydration of the cement, an exothermic reaction occurs, that is, heat is released, which is also accompanied by volume changes. When this heat is not dissipated efficiently, large tensile stresses can be generated, that are responsible for the well-known thermal cracking of concrete.

The crystalline network of the GO structure allows it to dissipate heat with great efficiency and even withstand intense electrical currents without heating up.

In the case of fresh concrete mixes, Graphenergy Construcción® promotes a more homogeneous heat distribution, minimizing the temperature gradient and volumetric changes, thus reducing the probability of thermal cracking.

In the case of hardened concrete, and even though it is an insulating material, when it is exposed to temperatures close to 400°C, its mechanical resistance is significantly compromised. The use of Graphenergy Construcción® reduces this risk, since it has been proven that its application generates a temperature difference 70% lower than the parameter required by the test between the exposed surface and the surface not exposed to fire.

Therefore, the contribution of the GO nanonetwork present in Graphenergy Construcción® helps to homogeneously distribute the hydration and setting temperature, reduces the risk of thermal cracking, increases the resistance of concrete at high temperatures and, finally, offers an excellent option sustainable for energy savings, particularly for those buildings whose geographical location requires the use of air conditioning equipment, achieving temperature reductions of up to 3 °C inside the buildings.

Drafting: EF/DHS

References

  1. Tanvir S., et al. Nano reinforced cement paste composite with functionalized graphene and pristine graphene nanoplatelets. Compos. B. Eng. 2020; 197: 15, 108063,
  2. Dong Lu., et al. Nano-engineering the interfacial transition zone in cement composites with graphene oxide. Constr. Build. Mater. 2022; 356: 129284,
  3. Peng Zhang., et al. A review on properties of cement-based composites doped with Graphene. J. Build. Eng. 2023: 70, 106367,
  4. WANG Qin et al., Research progress on the effect of graphene oxide on the properties of cement-based composites. New Carbon Mater. 2021; 36: 4,
  5. Junjie Chen, Effect of oxidation degree on the thermal properties of graphene oxide. j mater rest technol. 2020; 9:13740,
  6. Karthik Chintalapudi. The effects of Graphene Oxide addition on hydration process, crystal shapes, and microstructural transformation of Ordinary Portland Cement. J. Build. Eng. 2020; 32, 101551,
  7. Guojian Jing et al., Introducing reduced graphene oxide to enhance the thermal properties of cement composites. Cem Concr Compos. 2020; 109, 103559,
  8. Jinwoo An et al., Edge-oxidized graphene oxide (EOGO) in cement composites: Cement hydration and microstructure. Compos. B. Eng. 2019; 173, 106795

Improving protection and agricultural productivity

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Improving protection and agricultural productivity

thanks to plastic films with graphene oxide

The applications of plastic materials are very diverse, for use in agriculture, the formulation and development of plastic films for greenhouse covers, macrotunnels and microtunnels and for soil padding stands out. Among the most used plastic materials are Linear High Density Polyethylene (HDPE), Ethylvinylacetate (EVA), in the case of covers for structures, and Linear Low Density Polyethylene (LLDPE) as the main polymer for the manufacture of films for floor mulch.

Plastic films with the capacity to convert and transmit solar energy are materials of great interest for photothermal applications in agriculture. In this sense, the development of mulch films with good mechanical properties and photothermal conversion properties suitable for the agricultural field is still an urgent demand.

In recent years, graphene has attracted considerable attention due to its unique sheet structure, its extraordinary photothermal properties, and its mechanical properties.

To improve the solar conversion efficiency of plastic films, carbon-based nanomaterials such as: graphene (GnP), graphene oxide (GO) and reduced graphene oxide (RGO) can be incorporated, because they have excellent light absorption capacity with a wide spectral range (from ultraviolet to near infrared), and can convert light energy into heat energy (photothermal property).

Recent developments in the formulation of films, look for the blocking of UV radiation, the fluorescence effect, ultra-thermal films and more impermeable films. Other key properties desired in plastic films are mechanical resistance (greater durability), optical properties and anti-drip effect.

Recent studies have reported the values of water vapor permeability (WVP) in plastic films composed of graphene at different concentrations (0, 2, 4, 6 and 8% by weight). Where it was found that the water vapor permeability in the films continuously decreases (improves the barrier property) as the concentration of graphene in the films increases. This evaluation was carried out at different relative humidity (RH) percentages, where good performance in the barrier property could be observed at different humidity percentages (32%, 55% and 76%), see Fig. 1. When the graphene content increases up to 8% by weight, the WVP of the composite films decreases from 3.9 x10-10, 5.5 x10-10, and 7.6 x10-10g/m h Pa to 0.6 x10-10, 0.8 x10- 10, and 1.2 x10-10g/m·h·Pa at 32%, 55% and 76% relative humidity, respectively. This decrease in permeability is associated with the fact that graphene forms barriers at the molecular level in plastic films, giving rise to more tortuous paths for the diffusion of water vapor molecules or oxygen molecules, limiting their transportation through the plastic film. This reduction can also largely prevent evaporation and loss of water, a very valuable resource in these times of scarcity.

In Fig. 2, the stress curves of the graphene composite films are shown. It was found that the tensile strength of the films with graphene (2-8% by weight) increased up to 22.6 MPa compared to the virgin or control film (18.3 MPa). While the Young’s Modulus continuously increased from 95.7 to 171.2 MPa with the graphene content from 0 to 8% by weight, these results show an improvement in mechanical strength.

From the point of view of the horticulturist, the most relevant mechanical properties are: resistance to traction, tearing and impact. Tensile strength assesses the film’s ability to withstand tensile stresses and is very important when mounting the film to the padding.

Regarding advances in polymeric compounds with graphene and derivatives in solar energy conversion applications. Fig. 3 illustrates the photothermal conversion efficiency of the films on the soil surface. The photothermal conversion efficiency of graphene composite films was observed to gradually increase with graphene content.

The films composed at concentrations of 2,4,6 and 8% by weight of graphene, showed a higher photothermal conversion efficiency (10.1, 19, 26 and 40.3%) than the control film (6.7%) for a temperature of 27° C, indicating that graphene composite films can effectively adsorb light and can convert light energy into heat input that can rapidly increase soil temperature.

Interestingly, all graphene composite films showed better photothermal conversion performance to increase soil temperature compared to the control group. These results indicate that the composite films have good mechanical properties and adequate photothermal conversion properties that can potentially be used in mulch films to improve soil temperature and maintain soil moisture, which is beneficial for plant growth and production. agricultural crops.

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 and sells a wide range of masterbatches with graphene (graphene concentrate), with polymers widely used in agriculture and/or horticulture, such as LLDPE, LDPE, and HDPE. Our Masterbatches are granulated materials that act as multifunctional reinforcements for the production of more resistant plastic films with lower permeability and with a high degree of photothermal conversion.

References

  1. Melt processing and properties of linear low density polyethylene-graphene nanoplatelet composites. P. Khanam, M.A. AlMaadeed, M. Ouederni, E. HarkinJones, B. Mayoral, A. Hamilton, D. Sun. 2016, Vacuum , Vol. 130, págs. 63-71.
  2. Sun, Q., Geng, Z., Dong, J., Peng, P., Zhang, Q., Xiao, Y., & She, D. (2020). Graphene nanoplatelets/Eucommia rubber composite film with high photothermal conversion performance for soil mulching. Journal of the Taiwan Institute of Chemical Engineers.
  3. Effect of functionalized graphene on the physical properties of linear low density polyethylene nanocomposites. T. Kuila, S. Bose, A. K. Mishra, P. Khanra, N. H. Kim, J. H. Lee. 2012, Polymer Testing, Vol. 31, págs. 31-38.

The impact of graphene on the setting and strength of concrete

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The impact of graphene

on the setting and strength of concrete

Setting accelerating additives for cement-based structures are usually used when it is necessary to reach the desired resistance in less time, either to maintain continuous production or when the product needs to be put into operation immediately. However, the large number of variables that interfere in this process makes it difficult to accurately anticipate the acceleration that can be obtained with each new additive; without forgetting the importance of controlling the exothermic reaction or heat release that occurs during the setting or curing of the cement to avoid the appearance of thermal cracks in the final product.

To understand part of the reactions that occur during the setting of cement, it is important to know a little about its composition, for example: around 75% is made up of tricalcium silicate and dicalcium silicate which, when reacting with water, form calcium hydroxide and silicate. hydrated calcium (C-S-H), the latter being a nanometric component and, at the same time, the most important element, since the setting, hardening, resistance and dimensional stability of the cement depend on it.

Previous articles have discussed the interesting interaction of C-S-H nanoparticles with graphene oxide (GO) nanoparticles, another nanometric structure composed of carbon atoms and oxygen groups that has captured the attention of the construction industry thanks to its benefits during the hydration of cement and the direct impact it has to improve its mechanical resistance and durability, but also its interesting role as a setting accelerator, mainly for lightened polymeric concretes.

“GO acts as a catalytic agent during the cement hydration reaction”

The presence of oxygenated groups on the surface of GO allows it to absorb water and cement molecules to stabilize, on one hand, the atoms in the C-S-H by providing oxygen sites for the silicate chains and on the other, to act as a reservoir of water and transport channels to improve the hydration of cement.

In addition, the excellent compatibility of GO with different types of resins made it the perfect candidate for reinforcing polymer-type concrete that, although it does not contain a significant phase of hydrated cement, Portland cement is often used as a filling material and, thus giving the GO a larger array to transfer its properties to.

Graphenergy Construcción® is a water-based multipurpose additive with a specialized formula based on Graphene Oxide that contributes to improve the microstructure of any cement-based product, offering the following benefits during the setting process:

Setting: Acceleration of setting time up to 30%.

Drying: Helps uniform drying with fewer marks or moisture spots.

Increased resistance during demoulding of precast products: Greater integrity of the structures, better definition of angles and a significant reduction of product fracture.

Resistance to thermal changes: the good thermal conductivity of its formulation promotes a more homogeneous heat distribution during the hydration of the cement and, therefore, contributes to reducing the appearance of thermal cracks and reduces product fractures in cold climates.

Good integration with other additives or components of concrete mixes. It favors the workability of the mixtures.

Drafting: EF/DHS

Sources

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