Compounding NHFR Cable Jacketing Resins Using Polymer Modifiers
Making halogen-free or non-halogen flame-retardant (HFFR or NHFR) wire and cable compounds can benefit from using DuPont polymer modifiers. Often used as a replacement for previous coupling agents DuPont™ Fusabond® can significantly improve compound flexibility of cable jacketing while maintaining other properties like strength and elongation.
Typical levels of Fusabond® are in the range of 2-5 weight % based on the entire compound. Flame retardants that show affinity to Fusabond® include fillers such as alumina trihydrate (ATH) and magnesium hydroxide. Improved properties also can be seen when Fusabond® is used with common fillers such as calcium carbonate.
Extensive trials have been undertaken using the Fusabond® E family as a coupling agent in halogen-free flame retardant wire and cable formulations containing approximately 65% ATH in a LLDPE/EVA matrix.
DuPont™ Elvaloy® ethylene-based terpolymers can also be used in HFFR cables. By adding highly polar Elvaloy® terpolymers to the compound, oil and chemical resistance is improved, along with low-temperature flexibility. Other flexible, highly polar polymers such as high-VA content EVAs, are often harder to process, due to blocking of pellets, for example.