A novel phosphorus-silicon containing epoxy resin with enhanced thermal stability, flame retardancy and mechanical properties

A novel phosphorus-silicon containing epoxy resin (EF-P/Si) was prepared by introducing a phosphoric triamide (PTA) and epoxy-functionalized polysiloxane (EFP) into the Bisphenol F epoxy resin/4,4'-diaminodiphenyl methane (DDM) system to improve its flame retardancy and mechanical properties. PTA was synthesized by Triethyl phosphate and DDM and EFP was prepared by dimethyldimethoxysilane, dimethoxydiphenylsilane and 3-glycidoxy-propyltrimethoxysilane. TGA results demonstrated that EF-P/Si yielded a char residue of up to 16.6% at 700 degrees C. The measurements of flame retardancy showed that LOl value of EF-P/Si was 30.2, 50% higher than that of the pure epoxy resin and its UL-94 grade reached to V-1. A decomposition test under air was carried out to further investigate thermal stability of EF-P/Si. EF-P/Si exhibited a compact char structure which acted as a protective layer to inhibit the decomposition of the underlying matrix. EDX and FTIR verified that P-Si synergistic effect played a role in improving thermal stability of the char residue. The results of the mechanical property test showed that the incorporation of PTA and EFP significantly enhanced failure strain and K-IC of the epoxy resin without sacrificing its tensile strength, which was attributed to the increased free volume in the cured network and the excellent flexibility of the -Si-O-Si- skeleton in EFP. (C) 2019 Elsevier Ltd. All rights reserved.