Conductive thermoplastic compounds are often described by the conductive additive they contain. For the application, however, the important result is the electrical behavior of the molded or extruded article under defined conditions.
Dispersion, filler network, polymer matrix, shear history, orientation, geometry and conditioning can all influence measured resistance. The specification should therefore begin with the electrical window and the conditions under which it must be achieved.
Define the electrical function
Separate antistatic, static-dissipative, conductive and shielding requirements according to the actual application and applicable test basis.
Specify whether surface resistance, volume resistivity, shielding effectiveness or another electrical measure controls acceptance, together with geometry and conditioning where relevant.
Treat the conductive network as process-sensitive
Conductive performance emerges from the network formed by the additive in the polymer matrix. Compounding quality and subsequent molding or extrusion can alter dispersion, orientation and network continuity.
A laboratory plaque result should not automatically be assumed to represent every production geometry or processing condition.
Balance electrical and mechanical requirements
Conductive additives can change stiffness, impact, elongation, density, surface and rheology. Development should establish the lowest-risk formulation that meets the required electrical window while preserving the mechanical and processing needs of the part.
Measure variability, not only the average
Near a conductivity transition, modest formulation or process changes can produce larger electrical changes. Sampling should therefore consider part location, flow direction, lot and processing condition where those factors are relevant.
- Electrical test method
- Conditioning
- Part or specimen geometry
- Measurement locations
- Process condition
- Lot-to-lot variation
Qualify on representative production geometry
Close the development loop with parts or representative geometry produced under the intended process window. Confirm electrical performance together with dimensional, mechanical and surface requirements before approval.
Technical references
