Synthesis of a Multifunctional Phosphorus/Silicon Flame Retardant via an Industrial Feasible Technology

Green and efficient approach for fabricationphosphorus/siliconflame retardant with excellent toughness and dielectric property forepoxy resin High-performance and multifunctional epoxy resins arein increasingdemand in the booming electrical and electronic fields; however, thecomplexity and high cost of the process pose a huge challenge forits manufacture. Herein, two multifunctional phosphorus-siliconeflame retardants (DTEP and DDEDP) were synthesized by grafting rigidphosphaphenanthrene structure into a soft cyclic silicone epoxy resin,where the whole process is solvent-free, cost-effective, and a 100%atomic economy. The cured products containing 5 wt % DTEP and DDEDP(i.e., DTEP-5 and DDEDP-5) both can easily achieve a V-0 rating inthe UL-94 test and their limiting oxygen index values are 28.8% and29.1%, respectively. Compared to pure epoxy resin, the heat and smokeemissions of the optimal DTEP-5 sample were reduced by 30.8% and 31.5%during the combustion, and the toughness (impact strength) of DTEP-5was increased by 3.3 times without sacrificing their rigidity. Additionally,due to the superior electrical insulation capabilities and low surfaceenergy of silicone, DTEP and DDEDP impart epoxy resin with excellentdielectric and hydrophobic properties. This paper offers a facileand industrially feasible strategy for manufacturing multifunctionalepoxy resin and exhibits great promise in electrical and electronicfields.

Automated summary

This study successfully synthesized two multifunctional phosphorus-silicone flame retardants and applied them in epoxy resin using a solvent-free, cost-effective, and 100% atomic economy method. The cured samples containing 5% flame retardants showed V-0 level flame retardancy and high oxygen index values, reduced heat and smoke emissions during combustion, and increased toughness and electrical insulation capabilities.