What Is Conductive Polyurethane Material?

Most polymer materials typically exhibit a volume resistivity between 10¹⁰ and 10²⁰ Ω·cm, making them long used as electrical insulators. However, as the scope of polymer applications expands—especially with the rapid development of electronics and information technology—there is a growing demand for conductive polymer materials. These materials are not only easy to process, flexible, corrosion-resistant, and lightweight, but they also offer increasingly important functional benefits. Consequently, many international manufacturers are actively engaged in research and development of conductive polymers, and significant progress has been made in both materials science and industrial applications.

Conductive polymer materials can be categorized into two types: intrinsically conductive polymers and composite conductive polymers.

①Intrinsically conductive polymers derive their conductivity from their molecular structure or through specific blending processes.

②Composite conductive polymers are made by mixing a polymer matrix (such as polyurethane) with conductive fillers.

Among the various types of conductive fillers used in composite systems, the following are common:

①Carbon-based fillers – graphite, carbon black, and carbon fibers

②Metal-based fillers – metal powders, flakes, fibers, metal-coated glass fibers, and mica coated with nickel, copper, chrome, or stainless steel

③Other fillers – inorganic salts and metal oxides

Carbon black is the most widely used conductive filler. Naturally a semiconductor, it has a volume resistivity ranging from 0.1 to 10.2 Ω·cm. When carbon black particles are densely packed or their spacing is reduced to a few angstroms (10⁻¹⁰ m), a conductive network is formed. Carbon black is abundant, cost-effective, and provides stable conductivity, with tunable resistivity ranging from 10⁰ to 10⁸ Ω·cm. It is used for electrostatic discharge prevention, as a heating element, in high-conductivity applications, and in electrodes.

The conductive efficiency of carbon black depends heavily on its structure, particle size, and surface chemistry. Industrially, high-structure, small-particle types such as acetylene black are preferred for their low thermal weight loss and resistivity.

It’s important to note that carbon black only significantly improves conductivity when it reaches a percolation threshold, beyond which the conductive network becomes saturated and resistivity levels off. However, the stability of this network is sensitive. During the production of conductive polyurethane elastomers, mixing time must be carefully controlled. While sufficient mixing helps form the network, excessive mixing can damage it.

Shear forces during processing affect the orientation and dispersion of conductive networks. Research shows that different manufacturing methods influence conductivity in the following order: casting > blow molding > injection molding > extrusion > lamination. Additionally, higher molding temperatures can further reduce surface resistivity.