Author: Philippe Bichot
3 minutes read

EXPLORING FOUR TYPES OF ANTI-STATIC AGENTS FOR CONDUCTIVE FLOORING

What is the most essential parameter for you when choosing a conductive filler? Is it the required loading, the price, its influence on color and smoothness of the floor surface, or the stability of anti-static properties over time?

 

Achieving the targeted uniform conductivity level in epoxy and polyurethane self-leveling static dissipative floors is heavily dependent on choosing the right anti-static additive. This article compares chopped and milled carbon fibers, graphene nanotubes and antimony tin oxide (ATO), and identifies the so-called “price per property” for each conductive filler.

Parameter	Chopped carbon fiber	Milled carbon fiber	ATO	Graphene nanotubes
Working dosage	1—4 wt. %	1—10 wt. %	> 10 wt. %	0.01—0.04 wt. %
Resistance range (surface to ground)	1011-104Ω
Black dots on surface	possible	yes	none	none
Available color range	wide	limited	limited	wide
Floor thickness	min 2 mm	min 0.5 mm	up to 16 mils	any
Resistance remains stable after abrasion defects on surface	problematic	yes	yes	yes
Influence on mechanical perfomance	small negative	strong negative	small negative	none
Influence on rheology	small negative	strong negative	small negative	acceptable
"Hot spots" (resistance varies on surface)	possible	possible	possible	none
Stable resistance over time	yes	yes	yes	yes
Settling during storage	possible	possible	yes	minimal
Cost of anti-static property	acceptable	acceptable	high	acceptable

Strengths: ✅  Large variety of suppliers ✅  Good price per property

Weaknesses: ❌  Occurrence of insulative “hot spots” ❌  Problematic installation ❌  High cost of floors due to coating thickness ❌  Can’t be used without conductive primer

Carbon fiber is the most frequently applied anti-static agent for static dissipative flooring. Together, chopped and milled carbon fiber represent more than a half of the whole self-leveling anti-static flooring market share. They comprise 10–15 µm diameter carbon fibers based on coal tar pitch that are either chopped to a length of 2–6 mm or milled to a length of 0.13–2 mm. The working dosage for chopped carbon fiber is 1–2 wt.%, while for milled carbon fiber it is 1–6 wt.%. Both of these carbon fiber options have a good price per property ($0.2 – $1.5) because of the relatively low initial fiber price and concentration required.

However, because of the length of chopped carbon fiber (2 mm or longer), the thickness of the top/base layer must be at least as much. This limitation results in increased costs, as the top/base layer accounts for almost 60% of the total cost to the customer. Anti-static flooring with chopped carbon fiber has a better appearance than flooring containing milled carbon fiber, but is more sensitive to installation defects, and suffers from the occurrence of insulating “hot spots”.

Strengths: ✅  No black dots on the surface ✅  Little influence on rheology and durability

Weaknesses: ❌  High price per property ❌  Occurrence of insulative “hot spots” ❌  Graying effect due to high loading dosage

Conductive pigments, such as antimony tin oxide (ATO), are usually supplied in powder form. ATO has the highest price per property at around 5–12 $/kg, which is a result of the high initial high price of the additive combined with the high working dosage required of 8–20 wt.%.

Antimony tin oxide has a negative impact on the color of the floor the due to its high loading rate. Applying this anti-static pigment coating, applications are limited to 16 mm. Otherwise, if the coating is thicker, the ATO will settle, leaving an insulative surface. And because most ATO systems incorporate the ATO as a part C, variations can appear from mix to mix, resulting in “hot spots” or “dead spots”.

Strengths: ✅  100% ESD protection without “hot spots” ✅  Wide color range of flooring ✅  Reduced cost due to less raw material required ✅  Can be applied with standard equipment ✅  Can be used without conductive primer

Weaknesses: ❌  Need to follow dilution guideline

Graphene nanotubes (also known as single wall carbon nanotubes) are a relatively new product that is now being welcomed by the market. Their key advantage in comparison with traditional anti-static additives lies in the extremely low working dosage required to achieve the targeted level of conductivity – from as little as 0.01% of the total compound weight.

Thanks to their small diameter and high aspect ratio, this minimal dosage of graphene nanotubes is sufficient to create a uniform conductive network. Extra-low working dosages open the door to reducing the thickness of the ESD coating (as low as 25 microns DFT) and to a full color palette. Graphene nanotubes help to significantly reduce installation and maintenance time, yielding additional cost savings. Learn more about the performance of graphene nanotubes in ESD flooring

OCSiAl produces TUBALL graphene nanotube concentrates for anti-static epoxy and polyurethane flooring that make it easier to apply nanotubes in a standard manufacturing process. Request a sample of nanotube concentrate that suits your ESD flooring formulation:

Target system	Sovent-free epoxy		Solvent-based epoxy
Additive carrier	Plasticizer	Surfactant	Plasticizer & stabilizing agent
	Fatty acid glycidyl ester	Ethoxylated alcohol	Fatty acid glycidyl ester, ammonium salt of polyolefins-based derivative
Product	More info	More info	More info