Intrinsically flame-retardant polyamide 66 with high flame retardancy and mechanical properties

Area of Science:

• Polymer Chemistry
• Materials Science
• Flame Retardant Technology

Background:

• Achieving both high thermal stability and reactivity in phosphorus-based flame retardants for intrinsic flame-retardant polymers is challenging.
• Existing single phosphorus compounds often compromise one property for the other.

Purpose of the Study:

• To develop a strategy for enhancing the thermal stability of a reactive flame retardant, 4-(2-(((2-carboxyethyl)(phenyl)phosphoryl)oxy)ethoxy)-4-oxohexanoic acid (CPPOA).
• To synthesize intrinsic flame-retardant polyamide 66 (FRPA66) with improved flame retardancy and mechanical performance.

Main Methods:

• CPPOA was reacted with 1,6-diaminohexane to form a CPPOA salt, enhancing its thermal stability.
• The CPPOA salt was then copolymerized with PA66 salt to create flame-retardant polyamide 66 (FRPA66).

Main Results:

• The thermal stability of CPPOA was significantly improved through salt formation.
• FRPA66 incorporating 6 wt% CPPOA achieved an LOI of 27.2% and a V-0 vertical combustion rating.
• The synthesized FRPA66 maintained excellent mechanical properties, with tensile strength of 70 MPa and impact strength of 5.6 kJ m^-2.

Conclusions:

• The developed salt formation strategy effectively enhances the thermal stability of reactive phosphorus-based flame retardants.
• This approach yields intrinsic flame-retardant polymers (FRPA66) with a desirable balance of high flame retardancy and robust mechanical properties.
• The method shows significant potential for practical applications requiring advanced flame-retardant materials.