Novel phosphonated hardeners derived from diamino diphenyl sulfone for epoxy resins: Synthesis and one-pack flame-retardant formulation alongside dicyandiamide

•Novel phosphonated DDS-based epoxy hardeners induced higher thermal stability as well as latent curing potency for the epoxy resin networks. TGA results showed that either ER/Dicy/DDS-DPPC or ER/Dicy/DPPC-DDS-DPPC exhibited higher char yields and lower degradation rates comparing to the cured ER/Di...

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Bibliographic Details
Published in:Polymer degradation and stability 2022-05, Vol.199, p.109917, Article 109917
Main Authors: Kamalipour, J., Beheshty, M.H., Zohuriaan-Mehr, M.J.
Format: Article
Language:English
Subjects:
Additives
Chemical synthesis
Curing
Curing agent
Curing agents
Diaminodiphenylsulfone
Differential scanning calorimetry
Epoxy resin
Epoxy resins
Flame retardant
Flame retardants
Hardeners
Heat measurement
Latent hardener
Mechanical properties
NMR
Nuclear magnetic resonance
Phosphonated
Phosphorus
Reagents
Thermal analysis
Thermal stability
Thermodynamic properties
Thermogravimetric analysis
Viscometry
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Summary:•Novel phosphonated DDS-based epoxy hardeners induced higher thermal stability as well as latent curing potency for the epoxy resin networks. TGA results showed that either ER/Dicy/DDS-DPPC or ER/Dicy/DPPC-DDS-DPPC exhibited higher char yields and lower degradation rates comparing to the cured ER/Dicy. In addition, the flame-retardancy induction was preliminarily established by the hardeners to the thermosets and approved by cone calorimetry. Therefore, it is a generally impressive and facile approach to modify latent flame-retardant curing agents for ER by modifying DDS with DPPC. Taking advantage of the features, these one-pack flame-retardant epoxy materials can create a greater chance of several applications. Epoxy resins (ER) along with their curing agents and flame retardant additives are preferred to be formulated as a one-pack material. Increasing viscosity during storage and operation is a complicated problem for one-pack material. To resolve the above-mentioned problem, we conducted a synthesis on new phosphorus-containing curing agents of 4,4-diamino diphenyl sulfone (DDS) and diphenyl phosphoryl chloride (DPPC) to be taken advantage of alongside a combination of dicyandiamide (Dicy). The chemical structure of both of the synthesized compounds derived from DDS (i.e., DDS-DPPC and DPPC-DDS-DPPC) were characterized by FTIR, as well as 1H-, 13C- and 31P-NMR spectroscopies. Latency and curing behavior of ER/Dicy/DDS-DPPC and ER/Dicy/DPPC-DDS-DPPC were studied by viscometry and differential scanning calorimetry (DSC). The compounds’ cured products’ thermal properties went through an investigation via DSC, thermogravimetric analysis (TGA), and cone calorimetry. The results revealed that the novel phosphonated DDS-based epoxy hardeners induced higher thermal stability and latent curing potency for the ER networks. TGA results showed that either ER/Dicy/DDS-DPPC or ER/Dicy/DPPC-DDS-DPPC exhibited higher char yields and lower degradation rates than that of the cured ER/Dicy's. With the incorporation of new synthesized curing agents into epoxy resin, ER/Dicy/DDS-DPPC and ER/Dicy/DPPC-DDS-DPPC samples achieved UL-94 V-1 and V-0, respectively. During combustion, synthesized curing agents decomposed to produce phosphorus-containing compounds to form protective char layers in the condensed phase, and generated phosphorus-containing radicals which quenched the active radicals in the gaseous phase. DDS-DPPC and DPPC-DDS-DPPC demonstrated a bi-phase flame retard
ISSN:0141-3910
1873-2321
DOI:10.1016/j.polymdegradstab.2022.109917