A High-Phosphorus-Content Polyphosphonate with Combined Phosphorus Structures for Flame Retardant PET

Area of Science:

• Materials Science
• Polymer Chemistry
• Flame Retardancy

Background:

• Polyethylene terephthalate (PET) is widely used but lacks inherent flame retardancy.
• Developing effective flame retardants for PET is crucial for safety applications.

Purpose of the Study:

• To synthesize and evaluate a high-phosphorus-content polyphosphonate (PBDA) as a flame retardant for PET.
• To investigate the flame retardant mechanism of PBDA in PET.

Main Methods:

• Synthesis of PBDA containing phosphaphenanthrene (DOPO) and phenyl phosphonate groups.
• Incorporation of PBDA into PET at 10 wt% loading.
• Flame retardancy testing (UL-94, LOI) and analysis of heat/smoke release (pHRR, THR, TSR).
• Mechanism elucidation using TGA-FTIR, Py-GC/MS, real-time FTIR, and SEM.

Main Results:

• PBDA significantly improved PET's flame retardancy, achieving a UL-94 V-0 rating and increasing LOI to 28.7%.
• Addition of 10 wt% PBDA reduced pHRR by 80%, THR by 60.5%, and TSR by 21% compared to pure PET.
• PBDA acted through both gas-phase radical quenching and condensed-phase char formation, enhancing barrier properties.

Conclusions:

• PBDA is an effective flame retardant for PET, offering excellent self-extinguishing properties and reduced heat/smoke emissions.
• The dual flame retardant mechanism (gas and condensed phase) contributes to PBDA's high performance.
• PBDA shows potential for enhancing the safety of PET-based materials.