(Shanghai Kingcom Chemical Co., Ltd., Shanghai 201512, China)
Abstract: In this paper, new single-walled carbon nanotubes (SWCNTs) are used as conductive filler of anti-electrostatic selfleveling epoxy coatings, and the influence of SWCNTs filler on self-leveling epoxy coatings is studied. The results show that the volume resistivity of anti-electrostatic self-leveling epoxy floor coatings can reach 106 Ω·m with the a very small dosage (0.1%) of SWCNTs, while other properties of self-leveling epoxy floor coatings are not influenced by SWCNTs.
Even the slightest movements can generate and accumulate static electricity. Floors are often subject to friction, which tends to accumulate a large amount of electrostatic charges, which hinders the production process and affects product quality. In severe cases, it can cause fires, explosions and other accidents. Anti-static floor coatings can impart conductivity to the floor to eliminate the danger of static electricity. Therefore, in recent years, they have been widely used in electronics, microelectronics, communications, precision instruments, computers, aerospace and military and other high-tech industries. With the increasingly strict environmental protection regulations, solvent-free antistatic self-leveling epoxy floor coatings have become the main products of antistatic floor coatings due to their beautiful appearance and good comprehensive performance.
Antistatic floor coatings are functional coatings. They are made by adding conductive fillers to the coatings. The conductive fillers contact each other to create “conductive channels”, form continuous conductive networks, or approach each other. Due to the “tunneling effect”, electrons cross the barrier. Form an electronic distribution network. The conductive filler usually adopts conductive carbon fiber, metal filler, graphite powder, conductive mica, etc. To make it a conductive chain, a sufficient filling amount is required. However, the filling amount is too large, resulting in difficulty in dispersion, sedimentation of self-levelling thick coatings, and even uneven distribution of conductive fillers, and damage to the look and feel of the coating surface layer.
Carbon nanotubes have excellent electrical conductivity due to intrinsic properties such as quantum effects, size effects, surface effects, and quantum tunneling effects. Carbon nanotubes have been widely used for research due to their excellent electrical conductivity, but the difficulty of dispersing nanomaterials has become an obstacle to their practical application. In the experiment, modified single-walled carbon nanotubes were used as conductive fillers for self-leveling coatings, and antistatic epoxy self-leveling floor coatings with excellent antistatic properties were developed.
1 Experimental section
1.1 Main raw materials
modified single-walled carbon nanotubes (customized), epoxy curing agent (Ancamine 2883, air products), resin (GELR128, Hongchang Electronics), reactive diluent (AGE), leveling agent (BYK333), Defoamer (BYK055), filler.
1.2 Preparation of single-wall carbon nanotube antistatic epoxy self-leveling coating
Single-walled carbon nanotubes were diluted in batches using epoxy GELR128 and dispersed at high speed (1 200 r / min). After checking for uniform dispersion, add rheological agent, defoamer and other auxiliary agents in sequence. Stir at medium speed (600 r / min) and then add filler to disperse at high speed (1 000 r / min). Disperse evenly. See Table 1 for typical formulations of single-wall carbon nanotube antistatic epoxy self-leveling coatings.
Note: The two-group distribution ratio of epoxy self-leveling floor coatings: m [component A (epoxy curing agent)]: m (component B) = 1: 5.
1.3 Preparation of anti-static epoxy self-leveling floor coatings The
conventional anti-static floor coating construction process is used for base surface treatment, anti-static primer, conductive copper foil (net), and anti-static self-leveling surface coating. See Table 2 for construction process description.
1.4 Test method
Test instrument: ACLMODEL385 resistance tester (American ACL company).
Test Standard: SJ / T 11294—2018 “General Specification for Antistatic Floor Coatings”.
2 Results and discussion
2.1 Filler type
Filling modification of epoxy self-leveling with different conductive fillers. Table 3 shows the antistatic performance of the coating formed by conductive epoxy powder, conductive carbon fiber, and single-walled carbon nanotubes filled with modified epoxy self-leveling coating. The conductive powder is a composite conductive powder of four needle-shaped ZnOw and conductive mica. In order to achieve an ideal antistatic state, it needs to be filled with 20% (the amount of four needle-shaped ZnOw, mass fraction, the same hereinafter). To achieve the same antistatic performance, conductive carbon fibers only need about 1%, and single-walled carbon nanotubes can be less than about 0.1%.
According to the anti-static coating’s electrostatic conduction mechanism, the use of a large amount of conductive powder will contact the conductive fillers with each other to create a “conductive channel”, thereby forming a continuous conductive network. The small amount of conductive carbon fibers and single-walled carbon nanotubes can only form an electron circulation network through the “tunnel effect”. The intrinsic characteristics of single-walled carbon nanotubes make the tunneling effect more obvious and effective. Therefore, a smaller amount of single-walled carbon nanotubes can achieve better antistatic performance. At the same time, large fillers have problems such as micro-sedimentation and agglomeration, so they can have a negligible impact on the antistatic uniformity and appearance of self-leveling coatings.
2.2 Amount of single-walled carbon nanotubes A
large amount of conductive powder will obviously affect various properties of epoxy coatings. The single-walled carbon nanotubes have a very small effect due to their intrinsic properties. Figure 1 is the effect of the amount of single-walled carbon nanotubes on its antistatic performance and coating viscosity. It can be seen from FIG. 1 that the antistatic performance of epoxy self-leveling can be obviously improved to the required range by using very small amounts (<0.5%, mass fraction, the same hereinafter). When the amount is more than 1%, the improvement of antistatic performance is not very obvious, which more fully shows that the conduction mechanism of single-walled carbon nanotubes is a tunnel effect rather than a contact type conductive channel effect. When the amount of single-walled carbon nanotubes is less than 1%, the effect on the viscosity of the system is not obvious. As the amount of single-walled carbon nanotubes is increased to 2%, the viscosity of the coating will increase significantly. Therefore, using single-walled carbon nanotubes with an amount of <0.5% will achieve excellent epoxy self-leveling antistatic properties without affecting the viscosity and other properties of the epoxy self-leveling itself. From the influence of the high filling amount of single-walled carbon nanotubes on the viscosity, it is not difficult to see that a higher filling amount of conductive powder will seriously affect the viscosity of epoxy self-leveling coatings, thereby affecting its construction performance.
2.3 Effect of single-walled carbon nanotube filler on epoxy self-leveling coatings
Epoxy self-leveling coatings have a leveling property, which makes the coatings with full gloss, flatness, and smooth surface after construction and molding, which have important applications in the field of flooring. The addition of conductive fillers to make epoxy self-leveling more antistatic has attracted widespread attention. Through the way of high-filling conductive powder, the leveling performance of epoxy self-leveling will be destroyed. This can be adjusted by the coating formulation to meet the construction requirements. As mentioned above, Problems such as micro-sedimentation and agglomeration will no doubt affect the appearance of self-leveling coatings. Even if the conductive carbon fiber with a relatively small amount is filled, if the problems such as dispersion are not solved satisfactorily, it will cause apparent defects that are difficult to detect. The use of single-walled carbon nanotubes has little effect on epoxy self-leveling viscosity, color, and appearance due to the extremely low dosage. At the same time, as shown in Figure 1, the tunneling effect of single-walled carbon nanotubes makes it possible to achieve an excellent antistatic effect with a small amount, and it has good repeatability and linear relationship. It can effectively adjust the amount and antistatic performance through linear derivation. relationship.
2.4 Comprehensive performance of antistatic self-leveling floor coatings
Using single-walled carbon nanotubes, a new type of antistatic epoxy self-leveling coatings is prepared through conventional epoxy self-leveling production processes. Table 4 is the comprehensive performance of single-wall carbon nanotube antistatic epoxy self-leveling floor coatings.
Epoxy self-leveling coatings use customized single-walled carbon nanotubes as conductive fillers, which can achieve excellent antistatic performance at very small amounts (<0.5%, mass fraction). And single-walled carbon nanotubes have almost no effect on the original characteristics of epoxy self-leveling coatings. We will further improve carbon nanotubes and their applications in floor coatings, and launch better antistatic floor coatings.