Graphic showcasing various investigations on how hyperbranched polymers function as flame retardants
Source: BAM division Technical Properties of Polymeric Materials
The implementation of flame retardants can drastically improve the fire performance of plastics: their use promotes safety in technology and chemistry as they increase escape times in case of fire and can even prevent incipient fires. In many cases, the addition of flame retardants to polymers leads to unwanted changes to material properties like lowering the glass transition temperature, which can affect the mechanical properties. One of BAM’s tasks is to investigate the chemical mechanisms and modes of action of flame retardants, so as to ensure the continued safe use of future formulations.
One group of flame retardants combines multifunctionality with low impact on material properties: hyperbranched (hb) polymers. Their complex structure affords them special properties like high miscibility with and immobilization in polymer matrices, as well as reduced persistence, bioaccumulation, and toxicity, which are key factors for REACH compliance in the EU. Phosphorus-based hb polymers are ideal flame retardants particularly for epoxy resins, where material properties govern their effective use. The goal of the DFG-funded project (DFG SCHA 730/15-1; WU 750/8-1) was to gain a molecular understanding of the chemical mechanisms and modes of action of these macromolecules as additive flame retardants for epoxy resins: in several publications and in cooperation with the Max Planck Institute for Polymer Research in Mainz, the influence of complex architecture, O:N-ratio to phosphorus, role of sulfur and its oxidation state, and aromaticity of the polymer matrix were investigated. The multi-methodic approach via spectroscopic analysis and fire testing enabled the formulation of decomposition path models, which carry the potential to improve future formulations.
Hyperbranched phosphorus flame retardants: multifunctional additives for epoxy resins
A. Battig, J.C. Markwart, F.R. Wurm, B. Schartel
published in Polymer Chemistry, 10, 4346-4358, 2019
Matrix matters: Hyperbranched flame retardants in aliphatic and aromatic epoxy resins
A. Battig, J.C. Markwart, F.R. Wurm, B. Schartel
published in Polymer Degradation and Stability, 170, 108986, 2019
Sulfur’s role in the flame retardancy of thio-ether–linked hyperbranched polyphosphoesters in epoxy resins
A. Battig, J.C. Markwart, F.R. Wurm, B. Schartel
published in European Polymer Journal, 122, 109390, 2020
BAM, division Technical Properties of Polymeric Materials