After our Cable Assembly Outer Sheath/Jacket Performance Functions webinar, attendees submitted several great questions and we’d like to answer two in particular here that focus on performing a flammability test for cables.
Question 1: You spoke about the compounds and mentioned several times about cable assemblies flammability and the need to understand the application to match the flammability to. How much different would a cable with no flame retardancy be from a cable that is highly flame retardant?
Question 2: During the webinar it was mentioned that the cable jacket protected the inner components from damage, including the exposure to flames. If the jacket is exposed to flames wouldn’t it just either melt or burn away?
The short video below will answer both of these questions.
Cable Assembly Flammability Test Demonstration
The first sample being burned is illustrative of a cable assembly jacket with no flame retardant additives. This type of cable would not have any safety certifications associated with it and would have extremely limited applications it could be used in. The second sample being burned is illustrative of a cable jacket that consists of compounds specifically developed for use in plenum or air handling areas. This jacket does not ignite and does not give off any smoke or hazardous gas as it is being burned. This cable would carry the highest safety certifications available and be authorized for use in public buildings in any air handling areas.
As you can see during the video, the first cable jacket melts away rather quickly, and in doing so, exposes the components underneath. With the cable jacket gone, these inner-components are now exposed to the flame and ultimately ignite in a blaze of smoke and flames. The second cable’s jacket doesn’t combust though; the jacket chars, and the char actually protects the underlying components from being destroyed by the flame. It's always important to communicate environmental requirements and work with a cable manufacturer who understands what works best for your project.