Graphene oxide and graphene moved from research and development in academics and into the real world thanks to more than 1000 companies worldwide working on graphene production or using graphene and graphene oxide for various applications.
There has been an increase in products containing or using applied graphene appearing on the market. The coating rubber, construction, battery, bulk graphene and plastics industries are regularly launching new products.
The capability to ensure primary particles in the formulations heavily impacts the success of the various applications.
Graphene oxide is a randomly functionalized graphene, meaning that de-agglomerating and dispersing graphene in polymers and other materials is more challenging than de-agglomerating and dispersing graphene oxide in water.
The material also offers additional potentials to functionalize the material further without trouble.
In 2019, Yufei Ma (The Sixth Element), with Yanwu Zhu (University of Science and Technology; Hefei) and Yaxuan Zheng (The Sixth Element) published a summary of the status of the industrialization of graphene oxide and reduced graphene oxide, focusing on major applications.
The Sixth Element has successfully committed significant amounts of research in various applications and is the largest graphene oxide manufacturer worldwide with a current capacity of 1000 t/a.
One of the first fields The Sixth Element began working on is enhancing corrosion protection with graphene.
The Sixth Element began to develop an appropriate graphene type in 2012 as part of a challenge set by the Chinese government to find solutions to reduce the zinc content in corrosion protection primers.
The system developed by the Sixth Element showed superior performance by adding 1% of a specially-designed graphene type SE1132 to an epoxy primer system containing 25% of zinc dust (D50 – 13 µm), all based on dry film.
The system passed more than 3000 hours in neutral salt spray testing with only 50 µm dry film thickness.
This new system was first applied to a windmill tower in the later part of 2015.
Research on the system has since continued, and it is possible that a water-based epoxy zinc primer system using 45% zinc dust (D50 – 13 µm) and 1% SE1132 (all based on dry film) could easily pass 2400 hours of neutral salt spray testing using a 100 µm dry film.
The Sixth Element is able to demonstrate that significantly better salt spray testing results are also possible through the development of more formulations and a different type of graphene.
More than 4000 hours salt spray testing can be achieved with a 70 µm thick film using a solvent based 2k standard epoxy system with 0.45% SE1233 and 33.5% zinc dust (D50: 3 µm – 5 µm) (all based on dry substance).
Customers have confirmed the excellent performance of graphene when used in corrosion protection systems. Even lower concentrations of zinc and/or graphene are sufficient depending on the formulation.
The Sixth Element has formulated a light color primer for electrostatic spray application to demonstrate the capabilities of graphene.
4000 hours salt spray testing, 2K Epoxy -70 µm, 33.5 % zinc, 0.45 % SE1233. Image Credit: The Sixth Element (Changzhou) Materials Technology Co.,Ltd.
Light reflection values increased by 35% when carbon black was replaced with 3% of the graphene type SE1233, and other light-colored pigments were added to adjust the pigment volume concentration.
An improvement of up to 70% could be achieved, depending on the final formulation. This change can influence the amount of top-coat needed to attain the desired light color.
Electro-static primer – light reflection value: left carbon black, middle with 3 % SE1233, right: white colour reference. Image Credit: The Sixth Element (Changzhou) Materials Technology Co.,Ltd.
Graphene is an excellent additive for enhancing the abrasion resistance of polymer formulations, as shown in the literature.
The Sixth Element has been asked to prove in specific research projects if the value proposition of graphene enhancing abrasion resistance is equally effective when substrates such as leather are coated with a very thin polyurethane coating.
Heat introduction into the polymer is related to the abrasion of polymers. The abrasion causes the polymer to soften, and the polymer is rubbed from the surface.
The abrasion resistance of the polymer should be enhanced by improving the mechanical strength of the polymer network and increasing the softening temperature.
If graphene is chemically bonded within the polymer network, it has the highest impact on increasing the softening temperature of a polymer. This chemical bond is most effectively achieved by using a functionalized graphene.
This encouraged The Sixth Element to opt to use a modified graphene oxide SE2430, which is already randomly functionalized. During the polymerization of the polyurethane polymer, the modified SE2430 was added.
The system was then coated on leather products used for automotive seating. Taber test method with a 500 g weight (GB/T2726-2005) was used to conduct abrasion testing at room temperature.
The abrasion resistance increased by 17 times compared to the system without graphene by adding between 0.4 weight % and 0.8 weight % of the modified SE2430.
There was no change to the hardening and drying conditions of the polyurethane system. It was also observed that the aging properties of the polyurethane were positively influenced when modified SE2430 was added.
The mechanical strength of the polyurethane coating without containing SE2430 decreased by 72% when accelerated testing conditions with 2.5 W/m² at 50°C and over 9 hours were used.
A system with 0.8% of SE2430 added had a decrease of only 58% and an improvement of 150%.
Abrasion resistance of PU leather coating using different levels of graphene. Image Credit: The Sixth Element (Changzhou) Materials Technology Co.,Ltd.
This information has been sourced, reviewed and adapted from materials provided by The Sixth Element (Changzhou) Materials Technology Co.,Ltd..
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