EoW March 2013

Technical article

Foam fluoropolymer solutions and processing for insulating high performance cables By Gary G Thuot and Robert T Young, of DuPont Chemicals and Fluoroproducts, Wilmington, Delaware, USA

Abstract With the number of high performing dielectric materials available today, selecting the ideal insulating materials for high demand cables is a balance of performance, processability and cost. This paper will present electrical performance and selection criteria for foam fluoropolymer dielectrics. Establishing viable processing ranges and key processing considerations, which will provide a stable, repeatable process, will also be investigated. Foam fluoropolymers offer excellent electrical characteristics, low smoke and high temperature resistance. Typically fluoropolymers are used in applications where low smoke is required such as plenum cables, high temperature applications such as military specified cables and applications requiring resistance to soldering. Selecting the right polymer as it relates to product size and the electrical properties is important in obtaining a robust process and desired cable performance. Processing and monitoring equipment selection and their operation are important to producing quality product at high yields. The intent of this paper is to explain some of these key product and process characteristics and their effects on the process and performance.

The attenuation results ( Figure 2 ) are based upon actual 50-ohm cable samples produced using identical design and processing conditions but varying resin grades. As illustrated in Figure 2 , there can be a significant difference in the cable loss based on grade selection.

and dielectric wall thickness. Electrical performance, as the graph below indicates, can vary with resin composition. The dissipation factor data ( Figure 1 ) illustrates differences measured on solid plaques of various grades of DuPont™ Airquick FFR foam resins in their solid state (un-foamed).

▼ ▼ Figure 1 : Dissipation factor

Dissipation Factor

Frequency

▼ ▼ Figure 2 : Attenuation

Selecting the right material

Attenuation db

Considerations for selecting a foaming fluoropolymer resin for high performance cables include electrical/physical perfor- mance needs, product conductor size

Frequency(Ghz)

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March 2013

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