DuPont™ Teflon® PTFE was discovered in the 1930s but could not be melt extruded.  Modifications to polymer architecture led to the development of melt processible fluoropolymers such as Teflon® FEP, Teflon® PFA, and Tefzel® ETFE.  The ability to be melt extruded coupled with properties such as a low dielectric constant and low flammability has made materials such as Teflon® FEP and Teflon® PFA well suited for wire and cable applications.

Why Foamed Insulation

Today DuPont is pioneering innovations in the foaming of fluoropolymer resins in order to support the development of advanced TIA/EIA Category 6 and 10 gigabit (10G-BASE-T) communications cables.

Foaming fluoropolymer resin insulation reduces its dielectric constant, providing opportunities for miniaturization and weight savings because lower insulation wall thickness can be used. In addition, because this reduces dissipation factor the resulting insulated wire has lower capacitance and attenuation.   Foamed insulation also increases the relative velocity of data transmission over insulated wire.

Resin and processing requirements are highly dependent on construction.  For thicker wall constructions (i.e., coaxial RG cable) a resin with a lower melt flow rate (MFR) is used with higher void content using lower draw down tooling.  For thinner wall constructions (i.e., Category 6 and 10G-BASE-T cables) a higher MFR resins is used at a lower void content using higher draw down tooling.

Return Loss measures the amount of signal that is lost due to reflections along the length of the cable.  Successful use of foamed Teflon® FEP generates good adhesion of insulation to the copper conductor which in turn leads to improved return loss.

The above photos show the consistently small and uniform cell structure that can be achieved using Teflon® FEP foam products.

Nucleant type and loading affect processing and cell structure which impacts electrical performance.  Process variables typically used to control items such as diameter and capacitance can also have large impact on performance of finished cable products.  It is important to keep a good balance between finding a robust, stable process while maintaining desired electrical performance.

Foaming of DuPont™ Teflon® fluoropolymer resins such as Teflon® FEP and Teflon® PFA with gas injection provides a safe and economical way to produce plenum rated cables of reduced size with desirable electrical performance.