Expandable Graphite as a Multifunctional Flame-Retarding Additive for Highly Filled Thermal Conductive Polymer...

Area of Science:

• Materials Science
• Polymer Chemistry
• Fire Safety Engineering

Background:

• Polyamide 6 (PA6) is a versatile polymer requiring enhanced flame retardancy and thermal conductivity for specific applications.
• Developing multifunctional additives that improve both properties simultaneously is crucial for advanced material design.

Purpose of the Study:

• To evaluate expandable graphite (EG) and graphite (G) as additives in polyamide 6 (PA6) to enhance flame retardancy and thermal conductivity.
• To investigate the interplay between thermal conductivity, residue formation, and fire performance in highly filled PA6 systems.

Main Methods:

• Formulation of PA6 composites with varying wt.% of graphite (G) and expandable graphite (EG).
• Fire testing using UL-94, Limiting Oxygen Index (LOI), and cone calorimeter setups.
• Analysis of thermal conductivity and residue formation effects on fire behavior.

Main Results:

• Thermal conductivity significantly influences time to ignition but offers limited fire resistance once ignited.
• PA6 with 20 wt.% EG/50 wt.% G showed no measurable heat development in cone calorimeter tests.
• V0 classification in UL-94 tests was achieved with ≥70 wt.% G, ≥25 wt.% EG, or ≥20 wt.% EG/25 wt.% G.

Conclusions:

• Expandable graphite and graphite are effective multifunctional additives for PA6, improving both flame retardancy and thermal conductivity.
• Thermal conductivity is most effective in mitigating ignition under low heat impact and good heat dissipation conditions.
• Optimized formulations with EG and G can achieve high fire safety standards for PA6 composites.