Bio-Based Bisbenzoxazines with Flame Retardant Linker.
Thorben Sören Haubold1,2, Laura Puchot3, Antoine Adjaoud3,4
1Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, Wiener Strasse 12, 28359 Bremen, Germany.
Polymers
|December 28, 2021
Summary
A novel, partly bio-based flame retardant benzoxazine monomer (DOPO-PA-fa) was synthesized and demonstrated excellent thermal stability and fire resistance. This halogen-free compound significantly enhances the fire safety of benzoxazine blends.
Area of Science:
- Polymer Chemistry
- Materials Science
- Flame Retardant Technology
Background:
- Benzoxazine resins are high-performance thermosetting polymers with excellent thermal and mechanical properties.
- Developing effective, halogen-free flame retardants is crucial for improving the fire safety of polymers.
- Incorporating reactive flame retardants into polymer backbones offers enhanced permanence and performance.
Purpose of the Study:
- To synthesize a novel, partly bio-based, halogen-free flame retardant benzoxazine monomer.
- To evaluate the thermal stability and flame retardant properties of the synthesized monomer.
- To assess the monomer's performance when blended with other benzoxazine systems.
Main Methods:
- A four-step synthesis involving a DOPO-based flame retardant, ethylene carbonate, phloretic acid, furfurylamine, and paraformaldehyde.
- Characterization of the monomer using Nuclear Magnetic Resonance (NMR), Infrared (IR), and Mass Spectrometry (MS).
- Polymerization behavior monitored by Differential Scanning Calorimetry (DSC) and rheological analysis; thermal stability assessed via thermogravimetric analysis (TGA); flame retardancy evaluated using UL-94 tests and Limiting Oxygen Index (LOI).
Main Results:
- Successful synthesis of the halogen-free flame retardant benzoxazine monomer (DOPO-PA-fa).
- Polymerization initiated at approximately 200 °C, yielding poly(DOPO-PA-fa) (pDOPO-PA-fa) with high thermal stability (30% residual mass at 800 °C).
- Achieved a V-0 rating in UL-94 tests and a high LOI of 35%, demonstrating excellent flame retardancy. Blending significantly improved thermal stability and fire resistance of other benzoxazines.
Conclusions:
- The synthesized DOPO-PA-fa monomer is a promising, partly bio-based, halogen-free flame retardant for benzoxazine systems.
- The monomer exhibits superior thermal stability and flame retardancy, making it suitable for demanding applications.
- This work highlights a viable strategy for developing advanced flame-retardant polymers with improved fire safety characteristics.
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