Electrical Resistivity of Carbon-Black-Loaded Rubbers

Abstract

Uses are growing for rubbers with varying levels of resistivity. High electrical resistivity is very much essential in wire and cable insulation applications. Low levels of resistivity are needed for electrostatic discharge in phonograph records and many medical, industrial, and military products and for semiconductive cable compounds. The level of resistivity depends upon the number of contacts or near contacts between conductive particles in the rubber matrix. Loading level is obviously a major determinant in addition to physicochemical characteristics of the black. In the latter regard, the highly conductive grades are characterized by small particle size, high structure, high surface porosity, and low volatile content. One would, therefore, seek the reverse of those factors for high-resistivity rubbers. One of the goals of materials research now is to create new materials with physicomechanical properties tailored to a particular application and to understand the physical processes which determine the end properties. In this review, an attempt has been made to discuss the electrical properties of carbon-black-loaded rubber composites, a class of materials which covers the range from insulators to conductors. The carbon-black-loaded rubbers are formed by dispersing carbon black into the rubber. The compounding is done by adding the carbon black to the rubber, mixing at temperatures above Tg and subjecting the mixtures to high shears until a uniform blend is obtained. The carbon-black particles may be as small as 14 nm in diameter or as large as 300 nm, and they may be individually dispersed or agglomerated in micron-sized clusters. Morphology of the rubber has a profound effect on its electrical properties. High electrically resistive rubbers are becoming increasingly important. Their wide array of applications include antistatic products, shielding materials, insulating membranes, resistors, etc. In the vicinity of the crystalline transition region the rubber shows a dramatic resistivity increase which can be utilized for self-regulation processes. Compounds suitable for such various applications differ appreciably in the nature of their components and composition depending on the specific performance required.

Polypropylene nanosphere: particle size and crystal structure

“…The reinforcing fi ller materials such as carbon black, silica, iron, nickel particles, are usually used for rubber composites. These types of fi ller materials increase the Young's modulus, tensile strength and tear strength due to the interaction and anchoring of fi llers and the interface of matrix [6][7][8]. In coming times, polymer nanoparticles can exhibit improved performance of mechanical properties in thermoplastic materials, since the use of suffi cient amount of polymer segments in rubber composite increase mechanical properties, such as tensile strength, and decrease the elongation [9].…”

Mechanical Properties of Nanoparticle Chain Aggregates by Combined AFM and SEM: Isolated Aggregates and Networks

“…In the formulation of a rubber tire tread, the fillers may constitute 20−30% by weight. The mechanism by which reinforcing fillers enhance the mechanical properties of elastomers is not well understood, but it may result from filler−filler interaction and the interaction between rubber polymer molecules and filler networks. ,− Although much is known about the behavior of polymer molecules, much less is known about NCA mechanical properties. ,, …”

“…Compared with an isolated chain, a chain in a network will be entangled and cross-linked with its neighbors. The entanglements and cross links of network chains will restrain the movement and deformation of each chain, leading to a more stable and recoverable structure. , A well-known reinforcing filler, carbon black, also forms aggregate networks in filled rubber. ,, The filler network also plays an important role in enhancing the elastic behavior of filled elastomers. A better understanding of the nanoscale mechanical properties of the aggregate filler itself, such as the breaking force, tensile strength, Young's modulus, and the dynamic behavior of the aggregate networks, may help to explain the reinforcing mechanism of the filler−elastomer nanocomposite system.…”

Engineered Polymers in Packaging: Some Solutions to Prevent Electrostatic Discharge

“…In the four-terminal or four-point probes method, separate pairs of current-carrying and voltage-sensing electrodes are used [10]. The separation of current and voltage electrodes eliminates the lead and contact resistance from the measurement (for further discussions of the electrical resistivity measurements in polymers, see please [11][12][13]).…”