A Core-Shell Elastic Flame Retardant with Superior Migration Resistance for Fire-Safe and Toughened Polyamide 66

Area of Science:

• Materials Science
• Polymer Chemistry
• Flame Retardant Technology

Background:

• Halogen-free flame retardants often migrate in polyamide 66 (PA66) under harsh conditions, causing surface whitening.
• Aluminum diethylphosphinate (ADP) and melamine polyphosphate (MPP) commonly used in PA66 exhibit this migration issue.

Purpose of the Study:

• To develop a novel core-shell elastic flame retardant (SiR@FR) to overcome the migration challenge in PA66.
• To enhance the flame retardancy, migration resistance, and mechanical properties of PA66 composites.

Main Methods:

• A core-shell elastic flame retardant (SiR@FR) was synthesized by encapsulating polymethylsiloxane (SiR) onto ADP and MPP using a solution deposition method.
• The modified flame retardant was incorporated into PA66, and the resulting composite (PA66-5) was subjected to aging tests, flame retardancy evaluations (UL-94 V-0), and mechanical property assessments.

Main Results:

• PA66-5 demonstrated excellent migration resistance, showing no surface whitening after 480 hours of aging at 85 °C/85% relative humidity.
• The composite achieved a UL-94 V-0 rating and a 65% reduction in peak heat release rate.
• Impact strength increased by 21% due to improved toughness and alleviated stress concentration.

Conclusions:

• The SiR@FR encapsulation strategy effectively prevents flame retardant migration in PA66.
• The developed flame-retardant PA66 composites exhibit superior stability, flame retardancy, and mechanical properties.
• This approach offers a promising solution for demanding applications requiring durable and stable flame-retardant materials.